Magnetic field-boosted electrochemistry has recently emerged as an effective strategy to enhancing the catalytic capability in industrially profitable purposes. However, its utilization to enhance the quality of life of individuals has not been thoroughly investigated yet. Here, we have unveiled a static magnetic field-boosted electrocatalytic process for the dissociation of self-assembled β-amyloid (Aβ) aggregates, the major pathological hallmark of Alzheimer’s disease (AD). Cobalt-doped titanium oxide (Co-TiO2) electrode exhibits the repetitive boosting and recovery of electrical current density in response to an applied static magnetic field due to ferromagnetic cobalt dopants. According to our microscopic and spectroscopic analyses results, Co-TiO2 electrode successfully triggers the dissociation process of Aβ aggregate structure only with applied voltage. Besides, the dissociation efficacy of Co-TiO2 electrode against Aβ aggregates is boosted when a static magnetic field is applied in addition to the voltage. Our in vitro evaluation results demonstrate that Co-TiO2 electrode has biocompatibility and mitigating effect against Aβ-associated neurotoxicity. Also, our ex vivo evaluation results confirm that Co-TiO2 electrode can clear micrometer-sized and accumulated Aβ aggregates from AD mouse brain tissue. This work discovers a therapeutic potential of static magnetic field-boosted bioelectrocatalysis for future AD treatment.

Herein, the self-reinforced inductive effect derived from coexistence of both p- and n-type redox-active motifs in a single organic molecule is presented. Molecular orbital energy levels of each motif are dramatically tuned, which leads to the higher oxidation and the lower reduction potentials. The self-reinforced inductive effect of the symmetric bipolar organic molecule, N,N’-dimethylquinacridone (DMQA), is corroborated, by both experimental and theoretical methods. Furthermore, its redox mechanism and reaction pathway in the Li+-battery system are scrutinized. DMQA shows excellent capacity retention at the operating voltage of 3.85 and 2.09 V (vs Li+/Li) when used as the cathode and anode, respectively. Successful operation of DMQA electrodes in a symmetric all-organic battery is also demonstrated. The comprehensive insight into the energy storage capability of the symmetric bipolar organic molecule and its self-reinforced inductive effect is provided. Thus, a new class of organic electrode materials for symmetric all-organic batteries as well as conventional rechargeable batteries can be conceived.

Ecoflex is widely used in bioelectronics due to its outstanding properties of low modulus and large stretchability. For its use as an encapsulation layer in multi-channel wearable devices, a patterning procedure is essential. However, conventional patterning strategies for Ecoflex, such as soft lithography, punching, and laser ablation, lack sufficient quality and process compatibility. To address this, we propose a process-compatible method of patterning Ecoflex by developing Photo-patternable Ecoflex (PPE). The PPE layer, used as an encapsulation layer, effectively dissipates strain energy at homogeneous interfaces, resulting in a 50% increase in electrical conductance under 250% strain. Using PPE, we fabricated intrinsically stretchable multi-sensors that monitor bio-signals like glucose, lactate, pH, and humidity in sweat. These sensors maintain durable sensitivity under strain up to 50% and for 1000 cycles at 20% strain. Finally, we mounted these stretchable multi-chemical sensors on an arm to monitor glucose and lactate levels in sweat.

Solar-driven N2 fixation offers a green alternative to the highly energy-intensive Haber-Bosch process that releases more than 300 million metric tons of CO2 annually to form NH3. However, N2-reducing photoelectrochemical (PEC) studies have not elucidated how an oxidation reaction affects the N2 reduction reaction (NRR). Here, we report a bias-free PEC platform for N2 reduction to NH3 and H2O oxidation to O2 and H2O2. Under solar light, the molybdenum-doped bismuth vanadate-based photoanodes extract electrons from H2O and transfer them to the silicon photovoltaic-wired hematite photocathode. The light-absorbing cathode receives the electrons to drive the NRR, which is influenced by the H2O oxidation reaction’s conditions. Furthermore, the integration of PEC NRR with H2O2-dependent biocatalytic oxyfunctionalization achieves simultaneous synthesis of valuable chemicals on both electrodes. This work presents the first example of a PEC NRR platform coupled with H2O oxidation and H2O2-dependent oxygenation for unbiased chemical synthesis using N2, H2O, and sunlight.

The natural Z-schematic photosynthesis is a promising catalytic model for solar-to-chemical conversion. Here, we construct a Z-schematic, wireless photoelectrocatalytic (PEC) system (i.e., artificial leaf) for biocatalytic oxyfunctionalization of hydrocarbons. The monolithic leaf structure consists of a tandem photoanode-photocathode configuration that uses sunlight as the sole energy source to drive redox reactions. Under solar light, the ferric oxyhydroxide-coated, molybdenum-doped bismuth vanadate (FeOOH|Mo:BVO) photoanode extracts electrons from H2O electron feedstock and transfers the electrons to the conjugated polyterthiophene (pTTh) photocathode. Meanwhile, the pTTh photocathode absorbs FeOOH|Mo:BVO-filtered light for O2 reduction to H2O2. The in situ generated H2O2 activates unspecific peroxygenases (UPOs) to drive C-H oxyfunctionalization (e.g., hydroxylation and epoxidation) with an excellent enantioselectivity. Furthermore, we solve HO-mediated inactivation of UPOs using a cellulose membrane, which increases enzymatic productivity with a benchmark total turnover number of 128,000 among PEC and photocatalytic platforms that trigger UPO-mediated synthesis.

Upconversion nanoparticles (UCNPs), as near-infrared (NIR) absorbers, are promising materials for use in flexible NIR photodetectors, which can be applied for wearable healthcare applications due to their advantages in a broad spectral range, high photostability, and biocompatibility. However, to apply UCNPs in wearable and large-area integrated devices, water stability and micro-patterning methods are required. In this work, the UCNPs are encapsulated with a siloxane polymer (UCNP@SiOx) via a sol-gel process to enable photo-patternability and photo-stabililty in water conditions. The UCNP@SiOx can be photo-patterned down to micron-scale feature sizes and exhibit no significant decrease in upconversion photo luminescence (PL) intensities and PL decay time after immersion in water for 2 h. Moreover, UCNP@SiOx is evaluated by an in vitro biocompatibility test and found to be non-toxic. By integrating the UCNP@SiOx with MoS2 photo-transistors (MoS2+ UCNP@SiOx), the devices exhibit enhanced responsivity (0.79 A W-1) and specific detectivity (2.22 x 107 Jones), which are 2.8 times higher than in the bare MoS2 phototransistors, and excellent mechanical durability over 1000 cycles of 20% compression and re-stretch test. This work opens the way for the facile synthesis of water-stable and photo-patternable siloxane-encapsulated UCNPs and a strategy for fabricating high-performance flexible NIR phototransistors through wavelength conversion.

Biocatalytic photosynthesis combines the distinctive characteristics of redox biocatalysis and photocatalysis for solar-to-chemical conversion. Photocatalytic materials harvest renewable solar light to activate oxidoreductases that offer nature-inspired routes for sustainable chemical synthesis with unparalleled reaction selectivity. Here we begin with a conceptual discussion on solar-powered redox biocatalysis, describe the underlying molecular mechanisms and thermodynamics, and highlight recent advances in (i) photocatalytic activation of cell-free or whole-cell biocatalytic machineries (e.g., redox enzymes, acetogens, cyanobacteria), (ii) repurposing cofactor-dependent enzymes for their new-to-nature syntheses, (iii) chemical transformations by photoenzymes, and (iv) photoelectrocatalytic biosynthesis.

Minerals in the Earth’s crust have contributed to the natural functioning of ecosystems via biogeochemical interactions. Linnaeite is a cobalt sulfide mineral with a cubic spinel structure that promotes charge transfer reactions with its surroundings. Here we report the hidden feature of linnaeite mineral to dissociate Alzheimer’s β-amyloid (Aβ) oligomers under near-infrared (NIR) light irradiation. Alzheimer’s disease (AD) is a neurodegenerative disorder caused by the abnormal accumulation of self-assembled Aβ peptides in the elderly brain. The β-sheet structured pore-forming Aβ oligomer (βPFO) is the most neurotoxic species exacerbating the symptoms of AD. However, a therapeutic agent that is capable of inactivating βPFO has not yet been developed. Our microscopic and spectroscopic analysis results have revealed that NIR-excited linnaeite mineral can modulate the structure of βPFO by inducing oxidative modifications. We have verified that linnaeite mineral is biocompatible with and has a mitigating effect on the neurotoxicity of βPFO. This study suggests that minerals in nature have potential as drugs to reduce AD pathology.

Enzymes are the catalyst of choice for highly selective reactions, offering nature-inspired approaches for sustainable chemical synthesis. Oxidative enzymes (e.g., monooxygenases, peroxygenases, oxidases, or dehydrogenases) catalyze a variety of enantioselective oxyfunctionalization and dehydrogenation reactions under mild conditions. To sustain the catalytic cycles of these enzymes, constant supply with or withdrawal of reducing equivalents (electrons) is required. Being redox by nature, photocatalysis appears a natural choice to accomplish the electron-relay role, and many photoenzymatic oxidation reactions have been developed in the past years. In this contribution, we critically summarize the current developments in photoredoxbiocatalysis, highlight some promising concepts but also discuss the current limitations.

The accumulation of plastic waste poses a serious environmental threat. Here, non-recyclable microplastics are used as electron feedstocks that are broken down to produce value-added oxidation products and accelerate various redox biosynthetic reactions. A Zr-doped haematite photoanode extracts electrons from hydrolysed poly(ethylene terephthalate) (PET) microplastic solutions obtained from post-consumer PET waste, such as drinks bottles, and transfers the electrons to the bioelectrocatalytic site. Carbon-based cathodes receive the electrons to activate redox enzymes (for example, unspecific peroxygenase, L-glutamate dehydrogenase and ene-reductase from the old yellow enzyme family) that drive various organic synthetic reactions. These reactions include oxyfunctionalization of C-H bonds, amination of C=O bonds and asymmetric hydrogenation of C=C bonds. These photoelectrocatalytic-biocatalytic hybrid reactions achieve total turnover numbers of 362,000 (unspecific peroxygenase), 144,000 (L-glutamate dehydrogenase) and 1,300 (old yellow enzyme). This work presents a photoelectrocatalytic approach for integrating environmental remediation and biocatalytic photosynthesis towards sustainable solar-to-chemical synthesis.

The practical application of lithium-air batteries (LABs), which operate through electrochemical formation and decomposition of lithium peroxide (Li2O2), is limited by pure oxygen feeding. When using ambient air instead of pure oxygen, the detrimental lithium carbonate (Li2CO3) formation on the cathode surface accelerates, limiting the stable operation of LABs. Although redox molecules have been widely studied as a homogeneous catalyst to facilitate Li2O2 oxidation in LABs, their ability to decompose Li2CO3 has barely been explored. Here, we examined the catalytic effect of a series of organic redox mediators on removing Li2CO3. Systematic investigation confirms that the molecules with a redox potential higher than 3.7 V vs. Li/Li+ significantly lower the potential of Li2CO3 oxidation, for which the reaction mechanism was further supported by in situ gas analysis. This study suggests new possibilities of exploiting redox molecules to ensure efficient oxidation of both Li2O2 and Li2CO3 in LABs in ambient air.

Photoacoustic materials emit acoustic waves into the surrounding by absorbing photon energy. In an aqueous environment, light-induced acoustic waves form cavitation bubbles by altering the localized pressure to trigger the phase transition of liquid water into vapor. In this study, we report photoacoustic dissociation of beta-amyloid (Aβ) aggregates, a hallmark of Alzheimer’s disease, by metal-organic framework-derived carbon (MOFC). MOFC exhibits a near-infrared (NIR) light-responsive photoacoustic characteristic that possesses defect-rich and entangled graphitic layers that generate intense cavitation bubbles by absorbing tissue-penetrable NIR light. According to our video analysis, the photoacoustic cavitation by MOFC occurs within milliseconds in the water, which was controllable by NIR light dose. The photoacoustic cavitation successfully transforms robust, β-sheet-dominant neurotoxic Aβ aggregates into nontoxic debris by changing the asymmetric distribution of water molecules around the Aβ’s amino acid residues. This work unveils the therapeutic potential of NIR-triggered photoacoustic cavitation as a modulator of the Aβ aggregate structure.

Heat is a fundamental feedstock, where more than 80% of global energy comes from fossilbased heating process. However, it is mostly wasted due to a lack of proper techniques of utilizing the low-quality waste heat (<100 °C). Here we report thermoelectrobiocatalytic chemical conversion systems for heat-fueled, enzyme-catalyzed oxyfunctionalization reactions. Thermoelectric bismuth telluride (Bi2Te3) directly converts low-temperature waste heat into chemical energy in the form of H2O2 near room temperature. The streamlined reaction scheme (e.g., water, heat, enzyme, and thermoelectric material) promotes enantioand chemo-selective hydroxylation and epoxidation of representative substrates (e.g., ethylbenzene, propylbenzene, tetralin, cyclohexane, cis-β-methylstyrene), achieving a maximum total turnover number of rAaeUPO (TTNrAaeUPO) over 32000. Direct conversion of vehicle exhaust heat into the enantiopure enzymatic product with a rate of 231.4 uM h-1 during urban driving envisions the practical feasibility of thermoelectrobiocatalysis.

Pollen grains in nature possess highly hierarchical structure created through evolution process for over millions of years. Here, we report eco-friendly synthesis of highly photocatalytic metal oxides (ZnO, CeO2, and Fe2O3) using sporopollenin exine capsules (SECs), the hard structure of pollen, as a template. We generate carboxylate groups on the SECs to induce electrostatic interactions between the metal ions in the precursor solution and the surface of the SECs. The pollen-templated metal oxide structure is synthesized by aggregating metal oxide nanoparticles with the size of 10-20 nm on the micro-sized SECs framework, which have maintained unique morphology of the pollen. These metal oxides display excellent performance of organic pollutants degradation under visible light, owing to high surface area and oxygen vacancies which allow higher reaction rates and promote separation of photogenerated electron-hole pairs.

Flexible micro light-emitting diodes (f-μLEDs) have been regarded as an attractive light sourcefor the next-generation human-machine interfaces (HMI), thanks to their noticeable optoelectronicperformances. However, when it comes to their practical utilizations fulfilling industrial standards, there have been unsolved reliability and durability issues of the f-μLEDs, despite previous developments of the high-performance f-μLEDs for various applications. Herein, highly robust flexible μLEDs (f-HμLEDs) with 20 × 20 arrays, which are realized by a siloxane-based organicinorganic hybrid material (SHM), are reported. This work is the first demonstration of the flexible μLED encapsulation platform based on the SHM, which proved its mechanical, thermal, and environmental stabilities and biocompatibility, enabling us to envisage biomedical and/or flexible display applications using our f-HμLEDs.

The abnormal self-assembly of β-amyloid (Aβ) peptides and their deposition in the brain is a major pathological feature of Alzheimer’s disease (AD), the most prevalent chronic neurodegenerative disease affecting nearly 50 million people worldwide. Here, we report a newly discovered function of magnetoelectric nanomaterials for the dissociation of highly stable Aβ aggregates under low-frequency magnetic field. We synthesized magnetoelectric BiFeO3-coated CoFe2O4 (BCFO) nanoparticles, which emit excited charge carriers in response to low-frequency magnetic field without generating heat. We demonstrated that the magnetoelectric coupling effect of BCFO nanoparticles successfully dissociates Aβ aggregates via water and dissolved oxygen molecules. Our cytotoxicity evaluation confirmed the alleviating effect of magnetoelectrically excited BCFO nanoparticles on Aβ-associated toxicity. We found high efficacy of BCFO nanoparticles for the clearance of microsized Aβ plaques in ex vivo brain tissues of an AD mouse model. This study shows the potential of magnetoelectric materials for future AD treatment using magnetic field.

Each year, the pulp and paper industry produces approximately 50 million metric tons of lignin as waste, 95% of which is combusted or abandoned. Here, we report the use of lignin as a photocatalyst that forms H2O2 by O2 reduction and H2O oxidation under visible light. We investigated the photophysical and electronic properties of two lignin models, lignosulfonate and kraft lignin, by spectroscopic and photoelectrochemical analyses, and demonstrated the photoredox chemistry of lignin using these and other lignin models (for example, native-like cellulolytic enzyme lignin, artificial lignin dehydrogenation polymer and phenolic beta-aryl ether-type lignin dimer). Furthermore, the integration of lignin and H2O2-dependent unspecific peroxygenases (UPOs) enabled the highly enantioselective oxyfunctionalization of various C-H bonds. The use of lignin photocatalysts solves a number of the challenges relating to the sustainable activation of UPOs, notably, eliminating the need for artificial electron donors and suppressing the HO·-mediated inactivation of UPOs. Thus, the lignin-UPO hybrid catalyst achieved a total turnover number of UPO of 81,000 for solar-powered biocatalytic oxyfunctionalization in photochemical platforms.

The pulp and paper manufacturers generate approximately 50 million metric tons of lignin per annum, most of which has been abandoned or incinerated because of lignin’s recalcitrant nature. Here, we report bias-free photoelectrochemical (PEC) oxidation of lignin coupled with asymmetric hydrogenation of C=C bonds. The PEC platform consists of a hematite (α-Fe2O3) photoanode and a silicon photovoltaic-wired mesoporous indium tin oxide (Si/mesoITO) photocathode. We substantiate a new function of photoelectroactivated α-Fe2O3 to extract electrons from lignin. The extracted electrons are transferred to the Si/mesoITO photocathode for regenerating synthetic nicotinamide cofactor analogues (mNADHs). We demonstrate that the reduction kinetics of mNAD+s depend on their reduction peak potentials. The regenerated mNADHs activate ene-reductases from the old yellow enzyme (OYE) family, which catalyze enantioselective reduction of α,β-unsaturated hydrocarbons. This lignin-fueled biocatalytic PEC system exhibits an excellent OYE’s turnover frequency and total turnover number for photobiocatalytic trans-hydrogenation through cofactor regeneration. This work presents the first example of PEC regeneration of mNADHs and opens up a sustainable route for bias-free chemical synthesis using renewable lignin waste as an electron feedstock.

Modulating lithium metal deposition is vital for the realization of stable and energy-dense Li-metal batteries. Ionic liquid (IL) has been regarded as a promising electrolyte additive for a uniform Li deposition because its cation moiety forms a lithiophobic protective layer on Li protuberant tips. Despite recent advances in ILs for Li metal batteries, rational designs for IL additives are still in their infancy, and further improvement is required. Here, a new class of self-assembled protective layer based on the design of a new IL molecule enabling high-performance L-metal batteries is reported. For the first time, symmetric design of lithiophobic side chains is introduced to the IL cations. This symmetric design creates a self-assembled lithiophobic protective layer on Li protuberant tips, resulting in the smooth deposition of Li. Thus, the symmetric IL enables stable cycling of Li-LiFePO4 and Li-LiNi0.6Co0.2Mn0.2O2 (NCM622) batteries with an average Coulombic efficiency of ~99.8% over 600 cycles. In addition, the symmetric IL enables a practical thin Li (40 um)-NCM622 cell with an energy density of ~658 Wh kg-1 based on the cathode mass in a coin-type battery. This work proposes a design protocol for IL-based additives and provides a prospective way to highly efficient, long-lasting Li-metal batteries.

Infectious bacteria evolve fast into resistance to conventional antimicrobial agents, whereas treatments for drug resistance bacteria progress more slowly. Here, we report a universally applicable photoactivated antimicrobial modality through light-responsive carbon dot-embedding soft hyaluronic acid hydrogel (CDgel). Because of the innate nature of the infectious bacteria that produce hyaluronidase, applied hyaluronic acid-based CDgel breaks down via bacteria and releases carbon dots (CDs) into the infectious sites. The released CDs possess photodynamic capabilities under light irradiation, inducing 1O2 generation and growth inhibition of the infectious bacteria, S. aureus and E. coli (∼99% and ∼97%, respectively), in vitro. In particular, these photodynamic effects of CDs from CDgel have been shown to accelerate the healing of infected wounds in vivo, showing a higher wound regeneration rate as compared to that of untreated wounds. Our work demonstrates that the biocompatible and shape-controllable CDgel possesses therapeutic potential as a treatment modality for the light-driven control of drug-resistant bacterial infections.

The vaterite phase of CaCO3 exhibits unique characteristics, such as high porosity, surface area, dispersivity, and low specific gravity, but it is the most unstable polymorph. Here, we report lignin-induced stable vaterite as a support matrix for integrated artificial photosynthesis through the encapsulation of key active components such as the photosensitizer (eosin y, EY) and redox enzyme (l-glutamate dehydrogenase, GDH). The lignin-vaterite/EY/GDH photobiocatalytic platform enabled the regeneration of the reduced nicotinamide cofactor under visible light and facilitated the rapid conversion of α-ketoglutarate into l-glutamate (initial conversion rate, 0.41 mM h-1; turnover frequency, 1060 h-1; and turnover number, 39,750). The lignin-induced vaterite structure allowed for long-term protection and recycling of the active components while facilitating the photosynthesis reaction due to the redox-active lignin. Succession of stability tests demonstrated a significant improvement of GDH’s robustness in the lignin-vaterite structure against harsh environments. This work provides a simple approach for solar-to-chemical conversion using a sustainable, integrated light-harvesting system.

Photobiocatalysis is a green platform for driving redox enzymatic reactions using solar energy, not needing high-cost cofactors and redox partners. Here, we present a visible light-driven whole-cell platform for human P450 photobiocatalysis using natural flavins as a photosensitizer. Photoexcited flavins mediate NADPH/reductase-free, light-driven biocatalysis by human CYP2E1 both in vitro and in the whole-cell systems. Our in vitro tests demonstrate that the photobiocatalytic activity of CYP2E1 is dependent on the substrate type, the presence of catalase, and the acid type used as a sacificial electron donor. We found a protective effect of catalase against the inactivation of CYP2E1 heme by H2O2 and the direct transfer of photo-induced electrons to the heme iron not by peroxide shunt. Furthermore, the P450 photobiocatalysis in whole cells containing human CYPs 1A1, 1A2, 1B1, and 3A4 demonstrates the general applicability of the solar-powered, flavin-mediated P450 photobiocatalytic system.

Ternary chalcogenide materials have attracted significant interest in recent years because of their unique physicochemical and optoelectronic properties without relying on precious metals, rare earth, or toxic elements. Copper molybdenum sulfide (Cu2MoS4, CMS) nanocube is a biocompatible ternary chalcogenide nanomaterial that exhibits near infrared (NIR) photocatalytic activity based on its low band gap and electron-phonon coupling property. Here, we study the efficacy of CMS nanocubes for dissociating neurotoxic Alzheimers β-amyloid (Aβ) aggregates under NIR light. The accumulation of Aβ aggregates in the central nervous system is known to cause and exacerbate Alzheimers disease (AD). However, clearance of the Aβ aggregates from the central nervous system is a big challenge due to their robust structure formed through self-assembly via hydrogen bonding and side-chain interactions. Our spectroscopic and microscopic analyses results have demonstrated that NIR-excited CMS nanocubes effectively disassemble Aβ fibrils by changing Aβ fibril’s nanoscopic morphology, secondary structure, and primary structure. We have revealed that the toxicity of Aβ fibrils is alleviated by NIR-stimulated CMS nanocubes through in vitro analysis. Moreover, our ex vivo evaluation have suggested that the amount of Aβ plaques in AD mouses brain decreased significantly by NIR-excited CMS nanocubes without causing any macroscopic damage to the brain tissue. Collectively, this study suggests the potential use of CMS nanocube as a therapeutic ternary chalcogenide material to alleviate AD in future.

We unveil that the conformational change of the single organic molecule during the redox reaction leads to the impressive battery performance for the first time. We propose the model material, a phenoxazin-3-one derivative, as a new redox-active bio-inspired single molecule for the Li-ion rechargeable battery. The phenoxazin-3-one cathode delivered high discharge capacity (298 mAhg-1) and fast rate capability (65% capacity retention at 10 C). We elaborate the redox mechanism and reaction pathway of phenoxazin-3-one during Li+-coupled redox reaction. The molecular structure alteration of phenoxazin-3-one during lithium-coupled electron transfer reaction enables strong pi-pi interaction between 2Li-phenoxazin-3-one and carbon, which was evidenced by operando Raman spectroscopy and density functional theory calculation. Our work provides the in-depth understanding about the conformational molecular switch of the single molecule during Li+-coupled redox reaction and insight into the design of the new class of organic electrode materials.

Organic-inorganic hybrid perovskite nanoparticles (NPs) are a very strong candidate emitter that can meet the high luminescence efficiency and high color standard of Rec.2020. However, the instability of perovskite NPs is the most critical unsolved problem that limits their practical application. Here, an extremely stable crosslinked perovskite NP (CPN) is reported that maintains high photoluminescence quantum yield for 1.5 years (>600 d) in air and in harsher liquid environments (e.g., in water, acid, or base solutions, and in various polar solvents), and for more than 100 d under 85 C and 85% relative humidity without additional encapsulation. Unsaturated hydrocarbons in both the acid and base ligands of NPs are chemically crosslinked with a methacrylate-functionalized matrix, which prevents decomposition of the perovskite crystals. Counterintuitively, water vapor permeating through the crosslinked matrix chemically passivates surface defects in the NPs and reduces nonradiative recombination. Green-emitting and white-emitting flexible large-area displays are demonstrated, which are stable for >400 d in air and in water. The high stability of the CPN in water enables biocompatible cell proliferation which is usually impossible when toxic Pb elements are present. The stable materials design strategies provide a breakthrough toward commercialization of perovskite NPs in displays and bio-related applications.

Extracellular deposition of β-amyloid (Aβ) peptide aggregates is a major characteristic of Alzheimer’s disease (AD) brain. Because Aβ peptide aggregates aggravate neuropathy and cognitive impairment for AD patients, numerous efforts have been devoted to suppressing Aβ self-assembly as a prospective AD treatment option. Here, we report Aβ-targeting, red light-responsive carbon dots (CDs) and their therapeutic functions as a light-powered nano modulator to spatiotemporally suppress toxic Aβ aggregation both in vitro and in vivo. Our aptamer-functionalized carbon dots (Apta@CDs) showed strong targeting ability toward Aβ42 species. Moreover, red LED irradiation induced Apta@CDs to irreversibly denature Aβ peptides, impeding the formation of β-sheet-rich Aβ aggregates and attenuating Aβ-associated cytotoxicity. Consequently, Apta@CDs-mediated, photomodualtion modality achieved effective suppression of Aβ aggregation in vivo, which significantly reduced the Aβ burden at the targeted sites in the brain of 5xFAD mice by ~40% and ~25% according to imaging and ELISA analyses, respectively. Our work demonstrates the therapeutic potential of photomodulating CDs for light-driven suppression against Aβ self-assembly and related neurotoxicity.

Alzheimer’s disease (AD), the most common age-related neurodegenerative disorder, accompanies a massive degradation of neurons including axonal injury. Being an axonal neuron-specific protein, neurofilament light (NfL) is a novel blood biomarker that reflects the neurodegeneration in AD, but no attempt has been made yet to develop sensing platforms that target NfLs in blood serum or plasma. Here, we report three-dimensional cross-stacked Pt nanowire arrays for the ultrasensitive photoelectrochemical (PEC) detection of NfLs. We constructed the woodpile-like Pt nanowire array (PtWP)-based biocathode by printing multilayer Pt nanowire arrays in an orthogonal configuration and conjugating them with NfL-specific DA2 antibodies. According to our collective electrochemical analyses, the 5-layered PtWP electrode modified with DA2 antibodies exhibited high oxygen reduction activities due to the large electrochemical active surface area and the effective electron transfer properties. We have combined the DA2-PtWP biocathode with a water-oxidizing, iron oxyhydroxide-deposited bismuth vanadate (FeOOH/BiVO4) photoanode to assemble a bias-free PEC detection system. Powered by a white light-emitting diode, the unbiased PEC platform accurately recognizes NfLs in blood plasma with the limit-of-detection of 38.2 fg/mL and limit-of-quantification of 853 fg/mL, which is 40 times lower than the NfL levels in AD patients’ blood. This work demonstrates the first example of an NfL-targeting detection system exhibiting femtomolar sensitivity.

The valorization of lignin has a significant potential in producing commodity chemicals and fuels from renewable resources. However, the catalytic degradation of lignin is kinetically challenging and often requires noble metal catalysts to be used under harsh and toxic conditions. Here, we report on the bias-free, solar reformation of lignin coupled with redox biotransformation in a tandem structure of BiVO4 photoanode and perovskite photovoltaic. The tandem structure compensates for the potential gap between lignin oxidation and biocatalytic reduction through artificial Z-schematic absorption. We found that the BiVO4-catalyzed photoelectrochemical oxidation of lignin facilitated the fragmentation of high molecular weight lignin into smaller carboxylated aliphatic and aromatic acids. Lignin oxidation induced photocurrent generation at the photoanode, which enabled efficient electroenzymatic reactions at the cathode. This study successfully demonstrates the oxidative valorization of lignin as well as biocatalytic reductions (e.g., CO2-to-formate and α-ketoglutarate-to-L-glutamate) in an unbiased biocatalytic PEC platform, which provides a new strategic approach for photo-biocatalysis using naturally abundant renewable resources.

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder and affects more than 10% of the population aged over 65 worldwide. Despite considerable global efforts, AD patients can only be diagnosed after the onset of symptoms based on neuropsychological tests and neuroimaging. Because the changes in the levels of biomarkers associated with Aβ deposits and tau tangles precede the appearance of the first cognitive symptoms, accurate measurements of AD core biomarkers is critical for identifying asymptomatic AD patients and predicting disease progression. In this regard, significant efforts have been made to develop novel AD biomarker-targeting sensor platforms that have superb sensitivity and high accessibility. This review provides an overview of recent advances in optical and electrical sensing of core AD biomarkers in clinically relevant fluids such as the cerebrospinal fluid and human blood. We have summarized current challenges and future strategies for translating the sensing techniques discovered in the academic laboratories into clinical analytic platforms for early diagnosis of AD.

Inspired by natural photosynthesis, biocatalytic photoelectrochemical (PEC) platforms are gaining prominence for the conversion of solar energy into useful chemicals by combining redox biocatalysis and photoelectrocatalysis. Here, we report a dual biocatalytic PEC platform consisting of a molybdeneum (Mo)-doped BiVO4 (Mo:BiVO4) photoanode and an inverse opal ITO (IO-ITO) cathode that gives rise to the coupling of peroxygenase and ene-reductase-mediated catalysis, respectively. In the PEC cell, the photoexcited electrons generated from the Mo:BiVO4 are transferred to the IO-ITO and regenerate reduced flavin mononucleotide to drive ene-reductase-catalyzed trans-hydrogenation of ketoisophrone to (R)-levodione. Meanwhile, the photoactivated Mo:BiVO4 evolves H2O2 in situ via a two-electron water oxidation process with the aid of an applied bias, which simultaneously supplies peroxygenases to drive selective hydroxylation of ethylbenzene into enantiopure (R)-1-phenyl-1-hydroxyethane. This study shows that the deliberate integration of PEC systems with redox biocatalytic reactions can simultaneously produce valuable chemicals on both electrodes using solar-powered electrons and water.

Piezoelectric materials can evoke electrochemical reactions by transferring charge carriers to reactants upon receiving mechanical stimuli. We report a newly discovered function of piezoelectric bismuth oxychloride (BiOCl) nanosheets for dissociating Alzheimer’s β-amyloid (Aβ) aggregates through ultrasound-induced redox reactions. The accumulation of Aβ aggregates (e.g., Aβ fibrils, plaques) in the central nervous system is a major pathological hallmark of Alzheimer’s disease (AD). Thus, clearing Aβ aggregates is considered a key for treating AD, but the dissociation of Aβ aggregates is challenging due to their extremely robust structure consisting of β-sheets. BiOCl nanosheets are a biocompatible piezoelectric material with piezocatalytic activity in response to ultrasound. Our analyses using multiple spectroscopic and microscopic tools have revealed that BiOCl nanosheets effectively disassemble Aβ fibrils under ultrasound stimulation. Sono-activated BiOCl nanosheets produce piezo-induced oxidative stress, which effectively destabilizes the β-sheets in Aβ fibrils. In vitro evolution has also shown that sono-activated BiOCl nanosheets can effectively alleviate the neuro-toxicity of Aβ fibrils. Furthermore, ex vivo evolution demonstrated that amount of Aβ plaques in AD mouse’s brain slices was drastically reduced by treatment with sono-activated BiOCl nanosheets.

As a class of carbon-based nanomaterials, carbon dots (CDs) have attracted enormous attention because of their tunable optical and physicochemical properties, such as absorptivity and photoluminescence from ultraviolet to near-infrared, high photostability, biocompatibility, and aqueous dispersity. These characteristics make CDs a promising alternative photonic nanoagent to conventional fluorophores in disease diagnosis, treatment, and healthcare managements. This review describes the fundamental photophysical properties of CDs and highlights their recent applications to bioimaging, photomedicine (e.g., photodynamic/photothermal therapies), biosensors, and healthcare devices. We discuss current challenges and future prospects of photonic CDs to give an insight into developing vibrant fields of CD-based biomedicine and healthcare.

The abnormal accumulation of β-amyloid (Aβ) aggregates in the brain is a major pathological hallmark of Alzheimers disease (AD). We report near-infrared (NIR)-active CuBi2O4-based photocathodic platform that can target intact Aβ aggregates and dissociate them into nontoxic species. Due to its relatively narrow bandgap, CuBi2O4 exhibits strong absorption of NIR light, which allows for deeper tissue penetration and less photo-damage of tissues than those of visible light. Furthermore, its high stability in aqueous media, biocompatibility, and robustness against photo-corrosion makes CuBi2O4 an ideal material for medical applications. For targeted clearance of Aβ aggregates, we have conjugated the KLVFF peptide which specifically recognizes and captures Aβ aggregates on the surface of silver-doped CuBi2O4 (Ag:CuBi2O4). Upon illumination of NIR light with a cathodic bias, the KLVFF-immobilized Ag:CuBi2O4 (KLVFF-Ag:CuBi2O4) effectively dissociated β-sheet-rich, long and entangled Aβ fibrillary aggregates into small fragmented, soluble species through photo-oxygenation. We also verified that the KLVFF-Ag:CuBi2O4­ photocathode is biocompatible and effective in reducing Aβ aggregate-induced neurotoxicity. Our work demonstrates the potential of the KLVFF-Ag:CuBi2O4 platform for targeted disassembly of cytotoxic, robust Aβ aggregates with the aid of NIR energy and cathodic bias.

The use of neat reaction media, that is the avoidance of additional solvents, is the simplest and the most efficient approach to follow in biocatalysis. Here, we show that unspecific peroxygenase from Agrocybe aegerita (AaeUPO) can hydroxylate the neat model substrate cyclohexane. H2O2 was photocatalytically generated in situ by nitrogen-doped carbon nanodots (N-CNDs) and UV LED illumination. AaeUPO entrapment in alginate beads increased enzyme stability and facilitated the reaction in neat cyclohexane. NCNDs absorption in beads containing AaeUPO created a 2-in-1 heterogeneous photobiocatalyst that was active for up to seven days under reaction conditions and produced cyclohexanol, 2.5 mM. To increase productivity, the bead size and the photocatalyst-to-enzyme ratio have been identified as promising targets for optimisation.

A robust photovoltaic is essential for long-term redox biotransformations in biocatalytic photoelectrochemical (PEC) platforms. Here, we report a single Cu(In,Ga)Se2 (CIGS) solar cell for unbiased photobiocatalytic reduction reactions. The photoanode/CIGS/cathode tandem assembly drives cofactor-dependent biocatalytic CO2 reduction under visible light. Our PEC-PV tandem device achieves the longest reaction time of 72 h and the highest ever recorded turnover frequency and total turnover number of the cofactor of 0.236 h-1 and 11.2, respectively, for biocatalytic PEC production of formate through cofactor regeneration. This benchmark performance is attributed to the excellent PEC stability of the CIGS component; the substitution of CIGS with a perovskite solar cell (PSC) results in unstable generation of photocurrent and a lower concentration of formate under high-humidity environments because of the water-induced degradation of PSC. This work demonstrates the propriety of CIGS in robust PEC-PV tandems for artificial photosynthesis.

Peroxygenases have long inspired the selective oxyfunctionalization of various aliphatic and aromatic compounds due to their broad substrate spectrum and simplicity of catalytic mechanism. This study provides a proof-of-concept of piezobiocatalysis for the first time by demonstrating peroxygenase-catalyzed oxyfunctionalization reactions fueled by piezocatalytically generated H2O2. Bismuth oxychloride (BiOCl) generated H2O2 in situ via an oxygen reduction reaction under ultrasonic wave. Through the simple combination of water, ultrasound, rAaeUPO (unspecific peroxygenase), and BiOCl, the piezobiocatalytic platform accelerated selective hydroxylation of ethylbenzene to enantiopure (R)-1-phenylethanol . The BiOCl-rAaeUPO couple also catalyzed other representative substrates with high turnover frequency and selectivity. Overall, the BiOCl-rAaeUPO couple serves as a mechanical-to-chemical energy conversion platform for driving peroxygenase-catalyzed reactions under ultrasound.

Green plants convert sunlight into high-energy chemicals by coupling solar-driven water oxidation in the Z-scheme and CO2 fixation in the Calvin cycle. Here, we have interfaced formate dehydrogenase from Clostridium ljungdahlii (ClFDH) with a TiO2-deposited CuFeO2 and CuO-mixed (ClFDH-TiO2|CFO) electrode. In the biohybrid photocathode, TiO2 layer enhances the photoelectrochemical (PEC) stability of the labile CFO photocathode and facilitates the transfer of photoexcited electrons from the CFO to ClFDH. Furthermore, inspired by the natural photosynthetic scheme, we combined the photobiocathode with a water-oxidizing, FeOOH-deposited BiVO4 (FeOOH|BiVO4) photoanode to assemble a wireless Z-scheme biocatalytic PEC device as a semi-artificial leaf. The leaf-like structure fulfilled a bias-free biocatalytic CO2-to-formate conversion under visible light; its rate of formate production was 2.45 times faster than that without ClFDH. This work is the first example of wireless solar-driven semi-biological PEC system for CO2 reduction that uses water as an electron feedstock.

Lignin is the second most earth-abundant biopolymer having aromatic unit structures, but has received less attention than other natural biomaterials. Recent advances in the development of lignin-based materials, such as mesoporous carbon, flexible thin films, and fiber matrix, have found their way into applications to photovoltaic devices, energy storage systems, mechanical energy harvesters, and catalytic components. In this review, we summarize and suggest another dimension of lignin valorization as a building block for the synthesis of functional materials in the fields of energy and environmental applications. We cover lignin-based materials in the photovoltaic and artificial photosynthesis for solar energy conversion applications. The most recent technological evolution in lignin-based triboelectric nanogenerators is summarized from its fundamental properties to practical implementations. Lignin-derived catalysts for solar-to-heat conversion and oxygen reduction are discussed. For energy storage applications, we describe the utilization of lignin-based materials in lithium-ion rechargeable batteries and supercapacitors (e.g., electrodes, binders, and separators). We also summarize the use of lignin-based materials as heavy metal adsorbents for environmental remediation. This review paves the way to future potentials and opportunities of lignin as a renewable material for energy and environmental applications.

Alzheimer′s disease (AD) is the most prevalent neurodegenerative disorder. A key pathogenic event of AD is the formation of intracellular neurofibrillary tangles that are mainly composed of tau proteins. Here, we report on ultrasensitive detection of total tau (t-tau) proteins using an artificial electron donor-free, BiVO4-based photoelectrochemical (PEC) analysis. The platform was constructed by incorporating molybdenum (Mo) dopant and iron oxyhydroxide (FeOOH) ad-layer into the BiVO4 photoelectrode and employing a signal amplifier formed by horseradish peroxidase (HRP)-triggered oxidation of 3,3′-diaminobenzidine (DAB). Despite the absence of additional electron suppliers, the FeOOH/Mo:BiVO4 conjugated with the Tau5 antibody produced strong current signals at 0 V (vs. Ag/AgCl, 3 M NaCl) under the illumination of a white light-emitting diode. The Mo extrinsic dopants increased the charge carrier density of BiVO4-Tau5 by 1.57 times, and the FeOOH co-catalyst promoted the interfacial water oxidation reaction of Mo:BiVO4-Tau5 by suppressing charge recombination. The introduction of HRP-labeled Tau46 capture antibodies to the FeOOH/Mo:BiVO4-Tau5 platform produced insoluble precipitation on the transducer by accelerating the oxidation of DAB, which amplified the photocurrent signal of FeOOH/Mo:BiVO4-Tau5 by 2.07-fold. Consequently, the water oxidation-coupled, FeOOH/Mo:BiVO4-based PEC sensing platform accurately and selectively recognized t-tau proteins down to femtomolar concentrations; the limit of detection and limit of quantification were determined to be 1.59 fM and 4.11 fM, respectively.

Abnormal accumulation of β-amyloid (Aβ) peptide aggregates in the brain is a major hallmark of Alzheimer’s disease (AD). Aβ aggregates interfere with neuronal communications, ultimately causing neuronal damage and brain atrophy. Much effort has been made to develop AD treatments that suppress Aβ aggregate formation, thereby attenuating Aβ-induced neurotoxicity. Here, the design of Aβ nanodepletors consisting of ultralarge mesoporous silica nanostructures and anti-Aβ single-chain variable fragments, with the goal of targeting and eliminating aggregative Aβ monomers, is reported. The Aβnanodepletors impart a notable decline in Aβ aggregate formation, resulting in significant mitigation of Aβ-induced neurotoxicity in vitro. Furthermore, stereotaxic injections of Aβ nanodepletors into the brain of an AD mouse model system successfully suppress Aβ plaque formation in vivo up to ~30%, suggesting that Aβ nanodepletors can serve as a promising antiamylodoisis material.

Reports have recently been published on ultrathin biofluid barriers, which enable the long-term measurement of biological signals and exhibit conformability on nonlinear surfaces such as skin and organs. However, inorganic- and organic-based barriers have process incompatibility and high water permeability, respectively. Siloxane- (inorganic) based fluorinated epoxy (organic) hybrid materials (FEH) are demonstrated for bio-fluidic barrier and the biocompatibility and barrier performance for flexible electronic systems as solution-processed oxide thin-film transistors (TFTs) on 1.2 μm thick polyimide (PI) thin film substrate is confirmed. FEH thin film can be patterned as small as 10 μm through conventional photolithography. The fabricated solution-processed indium oxide TFTs with FEH barriers exhibit durable performance over 16 h with no dramatic change of transfer characteristics in phosphate-buffered saline (PBS) environment. Furthermore, to realize FEH barriers for flexible systems, the solution-processed indium oxide TFTs with FEH barriers on ultrathin PI substrate are demonstrated subjected to compression test and successfully measure the electrical properties with no irreversible degradation during 1000 cycles of mechanical testing in PBS.

Amyloid self-assembly is a powerful bottom-up approach for the synthesis of sophisticated organic nanostructures that possess fascinating structural flexibility. This study adds a new dimension to the research on amyloid self-assembly by expanding its scope to the field of photobiocatalysis. We demonstrate visible light-driven regeneration of nicotinamide adenine dinucleotide (NAD+) using solvatochromic Congo red (CR) hybridized with an amyloid-derived peptide (Fmoc-FF) nanostructure. In the course of an in-situ self-assembly process of Fmoc-FF peptides, CR molecules were hybridized into a Fmoc-FF nanofiber network through p-p interactions between the nonpolar fluorenyl group of Fmoc-FF and the aromatic moieties of CR. This hybridization made CR dyes capable of photoredox catalysis because the planarization of CR induced by the Fmoc-FF degenerated the twisted intramolecular charge-transfer state of the dye. The photocatalytic Fmoc-FF/CR hydrogel facilitated O2 reduction-coupled NAD+ regeneration under illumination. The NAD+ regeneration yield of the Fmoc-FF/CR hybrid was five times higher than that of free CR. The in-situ regenerated NAD+ activated NAD+ dependent redox enzymes for alcohol oxidation with a significantly high total turnover number of 42,953.

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder, affecting one in ten people aged over 65 years. Despite the severity of the disease, early diagnosis of AD is still challenging due to the low accuracy or high cost of neuropsychological tests and neuroimaging. Here, we report clinically accurate and ultrasensitive detection of multiple AD core biomarkers (t-tau, p-tau181, Aβ42, and Aβ40) in human plasma using densely aligned carbon nanotubes (CNTs). The closely packed and unidirectionally aligned CNT sensor array exhibits high precision, sensitivity, and accuracy, evidenced by a low coefficient of variation (< 6%), a femtomolar-level limit of detection, and a high degree of recovery (> 91.4%). By measuring the levels of t-tau/Aβ42, p-tau181/Aβ42, and Aβ42/Aβ40 in clinical blood samples, the sensor array successfully discriminates the clinically diagnosed AD patients from healthy controls with an average sensitivity of 90.0%, a selectivity of 90.0%, and an average accuracy of 88.6%.

Peroxygenases catalyze selective oxyfunctionalization of hydrocarbons with high conversion efficiencies using H2O2 as a key cosubstrate. Here, we report an unbiased photoelectrochemical (PEC) tandem structure consisting of a FeOOH/BiVO4 photoanode, a Cu(In,Ga)Se2 solar absorber, and a graphitic carbon nitride/reduced graphene oxide hybrid cathode for light-driven peroxygenase catalysis. Powered by sufficient photovoltage generated by the solar absorber, the PEC platform generates H2O2 in situ through reductive activation of molecular oxygen using water as an electron donor in the absence of external bias. The peroxygenase from Agrocybe aegerita catalyzed the stereoselective hydroxylation of ethylbenzene to (R)-1-phenylethanol with total turnover numbers over 43,300 and high enantioselectivity (ee > 99%) in the unbiased PEC tandem system.

Exploiting organic materials participating in the biological energy transduction processes can inspire the discovery of new electrode chemistry for rechargeable batteries, considering the analogy in their electrochemical reactions involving the redox activity. Nicotinamide adenine dinucleotide (NAD+) is one of the most well-known redox cofactors carrying electrons. Herein, we firstly report that intrinsically charged NAD+ motif can serve as an active electrode in electrochemical lithium cells. Through anchoring NAD+ motif by the anion-incorporation, redox activity of the NAD+ is successfully implemented in conventional batteries, exhibiting the average voltage of 2.3 V. We also show that the operating voltage and capacity are tunable by altering the anchoring anion species without modifying the redox center itself. This work not only demonstrates the redox capability of NAD+, but also suggests that anchoring the charged molecules with anion-incorporation is a viable new approach to exploit various charged biological cofactors in rechargeable battery systems.

Peroxygenases are very interesting catalysts for specific oxyfunctionalization chemistry. Instead of relying on complicated electron transport chains, they rely on simple hydrogen peroxide as stoichiometric oxidant. Their poor robustness against H2O2 can be addressed via in situ generation of H2O2. Here we report that simple graphitic carbon nitride (g-C3N4) is a promising photocatalyst to drive peroxygenase-catalyzed hydroxylation reactions. The system has been characterized outlining its scope but also its current limitations. In particular, spatial separation of the photocatalyst from the enzyme is shown as solution to circumvent the undesired inactivation of the biocatalyst. Overall, very promising turnover numbers of the biocatalyst of more than 60.000 have been achieved.

Nicotinamide adenine dinucleotide (NAD+) is a key redox compound in all living cells responsible for energy transduction, genomic integrity, lifespan extension, and neuromodulation. Here, we report a new function of NAD+ as a molecular photocatalyst in addition to the biological roles. Our spectroscopic and electrochemical analyses reveal light absorption and electronic property of two π-conjugated systems of NAD+ (HOMO-LUMO gap: 4.13 eV, LUMONicotinamide: -0.90 V, HOMONicotinamide: 3.23 V, LUMOAdenine: -2.89 V, HOMOAdenine: 1.24 V vs. Ag/AgCl). Furthermore, NAD+ exhibits a robust behavior against photodegradation under UV-Vis-NIR irradiation (λ: 260-900 nm). We demonstrate photocatalytic redox reactions driven by NAD+, such as O2 reduction, H2O oxidation, and the formation of metallic nanoparticles. Beyond the traditional role of NAD+ as a cofactor in redox biocatalysis, NAD+ executes direct photoactivation of oxidoreductases through the reduction of enzyme prosthetic groups. Consequently, the synergetic integration of biocatalysis and photocatalysis using NAD+ enables solar-to-chemical conversion with the highest-ever-recorded turnover frequency and total turnover number of 1263.4 h-1 and 1692.3, respectively, for light-driven biocatalytic trans-hydrogenation.

Bone contains an organic matrix composed of aligned collagen fibers embedded with nano-sized inorganic hydroxyapatite (HAp). Many efforts are being made to mimic the natural mineralization process and create artificial bone scaffolds that show elaborate morphologies, excellent mechanical properties, and vital biological functions. This study reports a newly discovered function of lignin mediating the formation of human bone-like HAp. Lignin is the second most abundant organic material in nature, and it exhibits many attractive properties for medical applications, such as high durability, stability, antioxidant and antibacterial activities, and biocompatibility. Numerous phenolic and aliphatic hydroxyl moieties exist in the side chains of lignin, which donate adequate reactive sites for chelation with Ca2+ and the subsequent nucleation of HAp through co-precipitation of Ca2+ and PO43-. Our results underpin the expectations for lignin-based biomaterials towards future biointerfaces and hard tissue engineering.

The electrocatalytic reduction of CO2 under low overpotential and mild conditions using redox enzyme is a propitious route for carbon capture and conversion. Here, we report bioelectrocatalytic CO2 conversion to formate by conjugating a strongly CO2-reductive, W-containing formate dehydrogenase from Clostridium ljungdahlii (ClFDH) to conductive polyaniline (PANi) hydrogel. The ClFDH in the hybrid electrode successfully gained electrons directly from PANi and exhibited high capability for electroenzymatic conversion of CO2 to formate at low overpotential without NADH. We describe a potential electron transfer pathway in the PANi-ClFDH bioelectrode based on multiple spectroscopic analyses and a QM/MM-based computational study. The 3D-nanostructured PANi hydrogel facilitated rapid electron injection to the active site of ClFDH. In the absence of NADH, the PANi-ClFDH electrode showed stable CO2-to-formate transformation at overpotential as low as 40 mV, with 1.42 μmol h-1 cm-2 conversion rate, 92.7% faradaic efficiency, and 976 h-1 turnover frequency.

The Z-scheme-inspired tandem photoelectrochemical (PEC) cells have received attention as a sustainable platform for solar-driven CO2 reduction. Here, we report on continuously 3D-structured, electrically conductive titanium nitride nanoshells (3D TiN) for biocatalytic CO2-to-formate conversion in a bias-free tandem PEC system. The 3D TiN exhibited a periodically porous network with high porosity (92.1%) and conductivity (6.72 × 104 S m-1), which allowed for high enzyme loading and direct electron transfer (DET) to the immobilized enzyme. We found that the W-containing formate dehydrogenase from Clostridium ljungdahlii (ClFDH) on the 3D TiN nanoshell was electrically activated through DET for CO2 reduction. At a low overpotential of 40 mV, the 3D TiN-ClFDH stably converted CO2 to formate at a rate of 0.34 μmol h-1 cm-2 and a faradaic efficiency (FE) of 93.5%. Compared to a flat TiN-ClFDH, the 3D TiN-ClFDH showed a 58 times higher formate production rate (1.74 μmol h-1 cm-2) at 240 mV of overpotential. Lastly, we succeeded in assembling a bias-free biocatalytic tandem PEC cell that converted CO2 to formate at an average rate of 0.78 μmol h-1 and a FE of 77.3% only using solar energy and water.

We report a siloxane-encapsulated upconversion nanoparticle hybrid composite (SEUCNP) that exhibits excellent photoluminescence (PL) stability for over 40 days even at elevated temperature, in high humidity, and in harsh chemicals. The SE-UCNP is synthesized through UV-induced free-radical polymerization of sol-gel derived UCNP-containingoligosiloxane resin (UCNP-Oligosiloxane). The siloxane matrix with random network structure by Si-O-Si bonds successfully encapsulates the UCNPs with chemical linkages between the siloxane matrix and organic ligands on UCNPs. This encapsulation results in surface passivation retaining intrinsic fluorescent properties of UCNPs under severe conditions (e.g., 85 °C, 85% relative humidity) and a wide range of pH (from 1 to 14). As an application example, we fabricate a two-color binary micro-barcode based on SE-UCNP via a low-cost transfer printing process. Under near-infrared irradiation, the binary-sequences in our barcode are readable enough to identify objects using a mobile phone camera. The hybridization of UCNPs with a siloxane matrix provides the capacity for highly stable UCNP-based applications in real environments.

The abnormal self-assembly of cerebral β-amyloid (Aβ) peptides into toxic aggregates is a hallmark of Alzheimer’s disease (AD). Here, we report on multifunctional carbon dots that can chelate Cu(II) ions, suppress Aβ aggregation, and photooxygenate Aβ peptides. Copper ions have high relevance to AD pathogenesis, causing Cu(II)-mediated Aβ aggregation and oxidative damage to neuronal cells. For effective conjugation with Cu(II)-bound Aβ complexes, we have designed carbon dots that possess nitrogen (N)-containing polyaromatic functionalities on their surface by employing o-phenylenediamine (OPD) as a polymerization precursor. We demonstrate that the pOPD-derived carbon dots exhibit multiple capabilities against Cu(II)-mediated Aβ aggregation. Furthermore, the pOPD-derived carbon dots exhibited dramatically enhanced absorption and fluorescence upon coordination with Cu(II) ions and effectively photooxygenated Aβ peptides. The photodynamically modulated Aβ residues lost the propensity to coordinate with Cu(II) and to assemble into toxic aggregates. This work demonstrates the potential of carbon dots as a multifunctional β-sheet breaker and provides a promising anti-amyloidogenic strategy for future Aβ-targeted AD treatments.

We report visible light-driven, asymmetric hydrogenation of C=C bonds using an ene-reductase from Thermus scotoductus SA-01 (TsOYE) and a light-harvesting dye (rose bengal, RB) co-immobilized in alginate hydrogel. Highly efficient encapsulation of RB in alginate hydrogel was achieved using the intrinsic affinity between TsOYE and RB, which allowed for the construction of robust RB-TsOYE-loaded alginate capsules. In the absence of NADH, the photobiocatalytic system facilitated asymmetric reduction of 2-methylcyclohexenone to an enantiopure (R)-2-methylcyclohexanone (ee>99%, max. conversion: 70.4%, turnover frequency: 1.54 min-1, turnover number: 300.2) under illumination. A series of stability tests revealed a significant enhancement of TsOYEs robustness in alginate hydrogel against heat and chemical denaturants. This study provides insight into a greener and sustainable approach of cofactor-free OYE catalysis for producing value-added chemicals using light energy.

Graphitic carbon nitride (GCN) is a two-dimensional, metal-free conjugate polymer that exhibits exceptional thermal and chemical stabilities, tempting electronic band structure, photosensitivity, and earth-abundance. Despite the potential of GCN as a photocatalyst, it suffers from a limited range of visible-light absorption with an edge wavelength of around 470 nm. Here, we report that amorphous carbon nitride (ACN) is a promising photocatalyst in comparison to GCN for solar-driven biotransformation via regeneration of nicotinamide cofactor (NADH). Under visible light (λ > 420 nm), NADH regeneration yields by ACN reached 62.3% within an hour whereas GCN hardly reduced NAD+ to NADH. The in-situ regenerated cofactor was consumed by redox enzymes to convert substrates into value-added chemicals. The remarkable photocatalytic activity of ACN originated from its unique microstructure that lacks hydrogen bonds linking polymeric melon units, leading to extended visible light absorption and less charge recombination. Our results suggest that ACN efficiently drives biocatalytic photosynthesis, simultaneously achieving exceptionally durable reusability and long-term catalytic stability.

The aberrant self-assembly of polypeptides into misfolded β-sheet-rich amyloid aggregates is closely associated with the pathogenesis of a variety of neurodegenerative disorders including Alzheimer’s, Parkinson’s, and Creutzfeldt-Jakob diseases. Central to monitoring amyloid formation in vitro has been thioflavin-T (ThT), which has been the most extensively utilized fluorescent probe. Here, we report the inhibition of the aggregation of Aβ42, the major isoform of β-amyloid found in disease-related amyloid deposits, by photosensitized ThT. Our data from 2D NMR and mass spectrometry and quantitative analysis from chemical kinetics give residue-specific information on how photosensitized ThT affects the chemical behavior of Aβ42 monomers and how such changes affect the kinetics and mechanism of aggregation. These results provide a detailed molecular understanding of the effects of photosensitizers on the aggregation behavior of Aβ42, and might facilitate the potential development of light-mediated therapeutic agents for Alzheimer’s disease.

Peroxygenases are receiving tremendous interest as catalysts for selective oxyfunctionalisation reactions, which require controlled supply of H2O2 to operate efficiently. They are rapidly inactivated in the presence of even small concentrations of H2O2. Here, we propose a photocatalytic system for the reductive activation of ambient O2 to produce H2O2 which uses the energy provided by visible light more efficiently based on the combination of wavelength-complementary photosensitizers. This approach was coupled to an enzymatic system to make formate available as sacrificial electron donor. The scope and current limitations of this approach are reported and discussed.

Redox biocatalysis has come to the forefront due to its excellent catalytic efficiency, stereoselectivity, and environmental benignity. The green and sustainable biotransformation can be driven by photoelectrochemical (PEC) platforms where redox biocatalysis is coupled with photoelectrocatalysis. The main challenge is how to transfer photoexcited electrons to (or from) the enzyme redox centers for effective biotransformation using solar energy. This review commences with a conceptual discussion of biocatalytic PEC platforms and highlights recent advances in PEC-based biotransformation through cofactor regeneration or direct transfer of charge carriers to (or from) oxidoreductases on enzyme-conjugated electrodes. Finally, we address future perspectives and potential next steps in the vibrant field of biocatalytic photosynthesis.

Cytochrome P450s are multifunctional redox enzymes that have high potential in drug development and fine chemical industry for the synthesis of steroids, lipids, vitamins, and natural products. Despite the immense potential of P450s, the dependence on nicotinamide cofactor (NADPH) and NADPH-P450 reductase (CPR) limits their employment in the chemical industry. Here, we present a visible light-driven platform for biocatalytic C-hydroxylation reactions using natural flavin molecules, especially flavin mononucleotide, as a photosensitizer. Employing visible light as a source of energy instead of nicotinamide cofactor, the bacterial CYP102A1 heme domain was successfully applied for photobiocatalytic C-hydroxylation of 4-nitrophenol and lauric acid in the absence of NADPH and CPR. We present a proof of concept that the photoactivation of flavins is productively coupled with the direct transfer of photoinduced electrons to the P450 heme iron, achieving photobiocatalytic C-hydroxylation reactions.

The abnormal aggregation of β-amyloid (Aβ) peptides is a hallmark of Alzheimer’s disease (AD) that affects more than 10% of the people over the age 60 world-wide. While the exact mechanism of neuronal loss and cognitive decline has not been elucidated yet, the amyloid hypothesis about the causative role of Aβ aggregation in AD pathology has been widely supported by the numerous in vivo and in vitro data. In this respect, many efforts have been made to explore therapeutic agents that can modulate the aggregation of Aβ, but none of the efforts succeeded in producing effective anti-Ab drugs for treating AD. This article provides an overview of recent attempts that have employed light energy to intervene with the self-assembly process of Aβ peptides via the generation of oxidative stress by photosensitizers, such as natural or synthetic dyes, light-responsive nanomaterials, and photoelectrochemical platforms. The underlying mechanism of photodynamic reactions suppressing Aβ aggregation and the dilemma in generating long-been-blamed oxidative stress are discussed by addressing the positive role of oxidative stress produced by the photosensitizers in the light-induced suppression of Aβ-mediated neurotoxicity. We have summarized current challenges and strategies to advance photo-induced inhibition and modulation of Aβ aggregation as a therapeutic option for treating AD in the future.

Redox enzymes catalyze fascinating chemical reactions with excellent regio- and stereo-specificity. Nicotinamide adenine dinucleotide cofactor is essential in numerous redox biocatalytic reactions and needs to be regenerated because it is consumed as an equivalent during the enzymatic turnover. Here we report on unbiased photoelectrochemical tandem assembly of a photoanode (FeOOH/BiVO4) and a perovskite photovoltaic to provide sufficient potential for cofactor-dependent biocatalytic reactions. We obtain a high faradaic efficiency of 96.2% and an initial conversion rate of 2.4 mM h-1 without an external applied bias for the photoelectrochemical enzymatic conversion of a-ketoglutarate to L-glutamate via L-glutamate dehydrogenase. In addition, we achieve a total turnover number and a turnover frequency of the enzyme as high as 108,800 and 6,200 h-1, respectively, demonstrating that the tandem configuration facilitates redox biocatalysis using light as the only energy source.

Amyloidogenic peptides can self-assemble into highly ordered nanostructures consisting of cross beta-sheet-rich networks that exhibit unique physicochemical properties and high stability. We have constructed light-harvesting amyloid nanofibrils by employing insulin as a building block and thioflavin T (ThT) as a amyloid-specific photosensitizer. The ability of the self-assembled amyloid scaffold to accommodate and align ThT in high density on its surface allowed for efficient energy transfer from the chromophores to the catalytic units in a similar way to natural photosystems. Insulin nanofibrils significantly enhanced the photoactivity of ThT by inhibiting non-radiative conformational relaxation around the central C-C bonds and narrowing the distance between ThT molecules that were bound to the beta-sheet-rich amyloid structure. We demonstrated that the ThT-amyloid hybrid nanostructure is suitable for biocatalytic solar-to-chemical conversion by integrating the light-harvesting amyloid module (for nicotinamide cofactor regeneration) with a redox biocatalytic module (for enzymatic reduction).

Light-driven activation of redox enzymes is an emerging route for sustainable chemical synthesis. Among redox enzymes, the family of old yellow enzymes (OYEs) dependent on the nicotinamide adenine dinucleotide cofactor (NADH) catalyzes the stereoselective reduction of α,β-unsaturated hydrocarbons. Here, we report OYE-catalyzed asymmetric hydrogenation through light-driven regeneration of NADH and its analogues (mNADHs) by N-doped carbon nanodots (N-CDs), a zero-dimensional photocatalyst. Our spectroscopic and photoelectrochemical analyses verified the transfer of photo-induced electrons from N-CDs to an organometallic electron mediator (M) for highly regioselective regeneration of cofactors. Light triggered the reduction of NAD+ and mNAD+s with the cooperation of N-CDs and M, and the reduction behaviors of cofactors were dependent on their own reduction peak potentials. The regenerated cofactors subsequently delivered hydrides to OYE for stereoselective conversions of a broad range of substrates with excellent biocatalytic efficiencies.

Bismuth vanadate (BiVO4) is an attractive, low-cost n-type semiconductor that exhibits excellent photoelectrocatalytic properties, chemical stability, and biocompatibility. This study reports a newly discovered function of BiVO4 dissociating highly stable, self-assembled amyloid aggregates associated with Alzheimer’s disease. We have developed a visible light-active, nanoporous BiVO4 photoelectrode-based platform for dissociating β-amyloid (Aβ) assemblies and alleviating Aβ aggregate-induced toxicity. Our multiple photochemical and microscopic analyses revealed that β-sheet-rich, long Aβ fibrils were effectively destabilized and broken into small-sized, soluble species by BiVO4 photoelectrode under illumination of a white light-emitting diode and an anodic bias. The photo-activated BiVO4 under anodic bias generated oxidative stress, such as superoxide ions and hole-derived hydrogen peroxide, which caused photooxidation of Aβ residues and irreversible disassembly of Aβ aggregates. The efficacy of photoelectrocatalytic dissociation of Aβ aggregates was enhanced by Mo-doped BiVO4, which facilitated the separation of electron-hole pairs by improving electron-transport properties of BiVO4. Furthermore, we verified that both pristine and Mo-doped BiVO4 photoelectrodes were nontoxic and effective in reducing Aβ-associated cytotoxicity. Our work shows the potential of BiVO4-based photoelectrode platforms for the dissociation of neurotoxic, highly stable Aβ assemblies using light energy.

Hydrogenases (H2ases) are benchmark electrocatalysts in H2 production, both in biology and (photo)catalysis in vitro. We report the tailoring of a p-type Si photocathode for optimal loading and integration of H2ase by employing a hierarchical inverse opal (IO) TiO2 interlayer. This proton reducing Si|IO-TiO2|H2ase photocathode is capable to drive overall water splitting in combination with a complementary photoanode. We demonstrate unassisted water-splitting by wiring Si|IO-TiO2|H2ase to a modified BiVO4 photoanode in a photoelectrochemical (PEC) cell during several hours of irradiation. Connecting the Si|IO-TiO2|H2ase to a photosystem II (PSII) photoanode provides proof-of-concept for an engineered Z-scheme that replaces the non-complementary, natural light absorber photosystem I by a complementary abiotic silicon photocathode.

Sodium-ion rechargeable batteries are a promising candidate for large-scale electrical energy storage systems due to the abundance of sodium resources. Herein, we report the development of carbon-incorporated NASICON-Na3V2(PO4)3 (NVP) as a cathode active material for Na-ion batteries using carboxymethyl cellulose (CMC) and sucrose as dual carbon sources. The interaction between CMC and sucrose resulted in the formation of a highly porous structure (surface area: 58.998 m2 g-1) with increased sp2 carbon species, facilitating mass and charge transportation. The specific capacity (104.99 mAh g-1) of dual-carbonized CMC/sucrose-NVP (CS-NVP) was close to the theoretical capacity (117.6 mAh g-1). Furthermore, the dual-carbonized NVP exhibited stable cyclability, showing a specific capacity of 75.04 mA g-1 even at a high rate of 20 C.

Biocatalytic transformation has received increasing attention in green synthesis of chemicals because of the diversity of enzymes, their superior catalytic activities and specificities, and mild reaction conditions. The idea of solar energy utilization in chemical synthesis through the combination of photocatalysis and biocatalysis provides an opportunity to make the "green" process greener. Oxidoreductases catalyze redox transformation of substrates by exchanging electrons at the enzyme active site, often with the aid of electron mediator(s) as a counterpart. Recent progress indicates that photoinduced electron transfer using organic (or inorganic) photosensitizers can activate a wide spectrum of redox enzymes to catalyze fuel-forming reactions (e.g., H2 evolution, CO2 reduction) and synthetically useful reductions (e.g., asymmetric reduction, oxygenation, hydroxylation, epoxidation, Baeyer-Villiger oxidation). This review provides an overview of recent advances in light-driven activation of redox enzymes through direct or indirect transfer of photoinduced electrons. The approaches and understanding in the construction of catalytic assemblies to activate different redox enzymes using organic dyes, carbon-based nanomaterials, semiconductors, and photoelectrochemical platforms are outlined. We discuss current technical challenges and strategies to advance photobiocatalytic transformation as a synthetic tool that meets an ever-increasing demand for sustainable chemistry.

In green plants, solar-powered electrons are transferred through sophistically arranged photosystems and are subsequently channelled into the Calvin cycle to generate chemical energy. Inspired by the natural photosynthetic scheme, we have constructed a photoelectrochemical cell (PEC) configured with protonated graphitic carbon nitride (p-g-C3N4) and carbon nanotube hybrid (CNT/p-g-C3N4) film cathode and FeOOH-deposited bismuth vanadate (FeOOH/BiVO4) photoanode for the production of industrially useful chiral alkanes using an old yellow enzyme homologue from Thermus scotoductus (TsOYE). In the biocatalytic PEC platform, photoexcited electrons provided by the FeOOH/BiVO4 photoanode are transferred to the robust and self-standing CNT/p-g-C3N4 hybrid film that electrocatalytically reduces flavin mononucleotide (FMN) mediator. The p-g-C3N4 promoted a two-electron reduction of FMN coupled with an accelerated electron transfer by the conductive CNT network. The reduced FMN subsequently delivered the electrons to TsOYE for the highly enantioselective conversion of ketoisophorone to (R)-levodione. Under light illumination (> 420 nm) and external bias, (R)-levodione was synthesized with the enantiomeric excess value of above 83%, not influenced by the scale of applied bias, simultaneously exhibiting stable and high current efficiency. Our results suggest that the biocatalytic PEC made up of economical materials can selectively synthesize high-value organic chemicals using water as an electron donor.

The self-assembly of beta-amyloid (Abeta) peptides into highly stable plaques is a major hallmark of Alzheimers disease. Here, we report visible light-driven dissociation of beta-sheet-rich Abeta aggregates into small, nontoxic fragments using ruthenium (II) complex {[Ru(bpy)3]2+} that functions as a highly sensitive, biocompatible, photoresponsive anti-Abeta agent. According to our multiple analyses using thioflavin T, bicinchoninic acid, dynamic light scattering, atomic force microscopy, circular dichroism, and Fourier transform infrared spectroscopy, [Ru(bpy)3]2+ successfully disassembled Abeta aggregates by destabilizing the beta-sheet secondary structure under illumination of white light-emitting diode light. We validated that photoexcited [Ru(bpy)3]2+ causes oxidative damages of Abeta peptides, resulting in the dissociation of Abeta aggregates. The efficacy of [Ru(bpy)3]2+ is attributed to reactive oxygen species, such as singlet oxygen, generated from [Ru(bpy)3]2+ that absorbed photon energy in the visible range. Furthermore, photoexcited [Ru(bpy)3]2+ strongly inhibited the self-assembly of Abeta monomers even at concentrations as low as 1 nM and reduced the cytotoxicity of Abeta aggregates.

Peptide self-assembly is a facile route to the development of bioorganic hybrid materials that have sophisticated nanostructures towards diverse applications. Here, we report the synthesis of self-assembled peptide (Fmoc-diphenylalanine, Fmoc-FF)/graphitic carbon nitride (g-C3N4) hydrogels for light harvesting and biomimetic photosynthesis through non-covalent interactions between aromatic rings in Fmoc-FF nanofibers and tris-s-triazine in g-C3N4 nanosheets. According to our analysis, the photocurrent density of the Fmoc-FF/g-C3N4 hydrogel was 1.8 times higher (0.82 μA cm-1) than that of the pristine g-C3N4. This is attributed to effective exfoliation of g-C3N4 nanosheets in the Fmoc-FF/g-C3N4 network, facilitating photo-induced electron transfers. The Fmoc-FF/g-C3N4 hydrogel reduced NAD+ to enzymatically active NADH under light illumination at a high rate of 0.130 mole g-1 h-1 and drove light-responsive redox biocatalysis. Moreover, the Fmoc-FF/g-C3N4 scaffold could well-encapsulate key photosynthetic components, such as electron mediators, cofactors, and enzymes, without noticeable leakage, while retaining their functions within the hydrogel. The prominent activity of the Fmoc-FF/g-C3N4 hydrogel for biomimetic photosynthesis resulted from the easy transfer of photo-excited electrons from electron donors to NAD+ via g-C3N4 and electron mediators as well as the hybridization of key photosynthetic components in a confined space of the nanofiber network.

Abnormal aggregation of β-amyloid (Aβ) peptides is a major hallmark of Alzheimer’s disease (AD). In spite of numerous attempts to prevent the β-amyloidosis, no effective drugs for treating AD have been developed to date. Among many candidate chemicals, methylene blue (MB) has proved its therapeutic potential for AD in a number of in vitro and in vivo studies; but the result of recent clinical trials performed with MB and its derivative was negative. Here, with the aid of multiple photochemical analyses, we first report that photoexcited MB molecules can block Aβ42 aggregation in vitro. Furthermore, our in vivo study using Drosophila AD model demonstrates that photoexcited MB is highly effective in suppressing synaptic toxicity, resulting in a reduced damage to the neuromuscular junction (NMJ), an enhanced locomotion, and decreased vacuole in the brain. The hindrance effect is attributed to Aβ42 oxidation by singlet oxygen (1O2) generated from photoexcited MB. Finally, we show that photoexcited MB possess a capability to disaggregate the pre-existing Aβ42 aggregates and reduce Aβ-induced cytotoxicity. Our work suggests that light illumination can provide an opportunity to boost the efficacies of MB toward photodynamic therapy of AD in future.

The self-assembly of amyloidogenic peptides into β-sheet-rich aggregates is a general feature of many neurodegenerative diseases, including Alzheimers disease, which signifies the need for the effective attenuation of amyloid aggregation toward alleviating amyloid-associated neurotoxicity. In the present study, we report that photoluminescent carbon nanodots (CDs) can effectively suppress Alzheimers β-amyloid (Aβ) self-assembly and function as a β-sheet breaker disintegrating preformed Aβ aggregates. We synthesized CDs using ammonium citrate through one-pot hydrothermal treatment and passivated their surface with branched polyethylenimine (bPEI). The bPEI-coated CDs (bPEI@CDs) exhibited hydrophilic and cationic surface characteristics, which interacted with the negatively charged residues of Aβ peptides, suppressing the aggregation of Aβ peptides. Under light illumination, bPEI@CDs displayed a more pronounced effect on Aβ aggregation and on the dissociation of β-sheet-rich assemblies through the generation of reactive oxygen species from photoactivated bPEI@CDs. We verified the light-triggered attenuation effect of Aβ aggregation using a series of experiments, including photochemical and microscopic analysis. Furthermore, our cell viability test confirmed the ability of photoactivated bPEI@CDs for the suppression of Aβ-mediated cytotoxicity, indicating bPEI@CDs’ potency as an effective anti-Aβ neurotoxin agent.

Enoate reductases from the family of Old Yellow Enzymes (OYEs) can catalyze stereoselective trans-hydrogenation of activated C=C bonds. Despite their potential, however, their application is limited by the necessity for continuous supply of redox equivalents such as nicotinamide cofactors [NAD(P)H]. Here, we report visible light-driven activation of OYEs through NAD(P)H-free, direct transfer of photoexcited electrons from xanthene dyes to the prosthetic flavin moiety. Our spectroscopic and electrochemical analyses verified spontaneous association of rose bengal and its derivatives with OYEs. Illumination of a white light-emitting-diode triggered photoreduction of OYEs by xanthene dyes, which facilitated the enantioselective reduction of C=C bonds in the absence of NADH. The photoenzymatic conversion of 2-methylcyclohexenone resulted in enantiopure (ee >99%) (R)-2-methylcyclohenanone with conversion yields as high as 80-90%. The turnover frequency was significantly affected by the substitution of halogen atoms in xanthene dyes. The NADH-free, xanthene-sensitized photobiocatalytic platform was successfully applied to different homologues of OYEs from Thermus scotoductus and Bacillus subtilis. This work demonstrates a simple and versatile way of activating OYEs by direct coupling of OYE-catalysis with molecular photocatalysis.

Biomineralization is a biogenic process that produces elaborate inorganic and organic hybrid materials in nature. Inspired by the natural process, this study explores novel mineralization approach to create nanostructured CaCO3 films composed of amorphous CaCO3 hemispheres using catechol-rich polydopamine (PDA) as a biomimetic mediator. We successfully transformed thus-synthesized biomimetic CaCO3 to nanostructured films of metal oxide minerals, such as FeOOH, CoCO3, NiCO3, and MnOOH, via a simple procedure. CaCO3-templated metal oxide minerals functioned as an efficient electrocatalyst; CaCO3-templated CoPi (nanoCoPi) film exhibited high stability as a water oxidation electrocatalyst with a current density of 1.5 mA cm-2. The nanostructure of nanoCoPi consisting of individual nanoparticles (~70 nm) and numerous internal pores (BET surface area: 3.17 m2g-1) facilitated an additional charge transfer pathway from the electrode to individual active sites of catalysts. This work demonstrates a plausible strategy for facile and green synthesis of nanostructured electrocatalysts through biomimetic CaCO3 mineralization.

Organic redox compounds represent an emerging class of cathode materials in rechargeable batteries for low-cost and sustainable energy storage. However, the low operating voltage (< 3 V) and necessity of using lithium-containing anodes have significantly limited their practical applicability to battery systems. Here, we introduce a new class of p-type organic redox centers based on N, N’-substituted phenazine (NSPZ) to build ready-to-charge organic batteries. In the absence of lithium-containing anodes, NSPZ cathodes facilitate reversible two-electron transfer at 3.7 and 3.1 V accompanying anion association, which results in a specific energy of 622 Wh kg-1 in dual-ion batteries.

Natural photosynthesis is an effective route for clean and sustainable conversion of CO2 to high-energy chemicals. Inspired by the natural scheme, we designed a tandem-photoelectrochemical (PEC)-cell-integrated-with-enzyme-cascade (TPIEC) system, which transfers photogenerated electrons to a multi-enzyme cascade for biocatalyzed reduction of CO2 to methanol. We applied a hematite photoanode and a bismuth ferrite photocathode to fabricate the iron oxide-based tandem PEC cell for visible light-assisted regeneration of nicotinamide cofactor (NADH). The cell utilized water as an electron donor and spontaneously regenerated NADH. To complete the TPIEC system, a superior three-dehydrogenase cascade system was employed in the cathodic part of the PEC cell. Using applied bias, the TPIEC system achieved high methanol conversion output, providing a PEC platform for highly selective synthesis of hydrocarbon fuel using readily-available solar energy and water.

Peroxygenases are very promising catalysts for oxyfunctionalization reactions. Their practical applicability, however, is hampered by their sensitivity against the oxidant (H2O2), therefore necessitating in situ generation of H2O2. Here, we report a photoelectrochemical approach to provide peroxygenases with suitable amounts of H2O2 while reducing the electrochemical overpotential needed for the reduction of molecular oxygen to H2O2. When tethered on single-walled carbon nanotubes (SWNT) under illumination, flavins allowed for a marked anodic shift of the oxygen reduction potential in comparison to pristine-SWNT and/or non-illuminated electrodes. This flavin-SWNT-based photoelectrochemical platform enabled peroxygenases-catalyzed, selective hydroxylation reactions.

We report a photoelectrocatalytic way for suppressing beta-amyloid (Abeta) self-assembly using a visible light-active, hematite-based photoelectrode platform. Upon illumination of a light-emitting diode with anodic bias, we found that hematite photoanodes generate reactive radical species such as superoxide ions and hydroxyl radical via the photoelectrocatalytic process. According to our analyses, the hole-derived radicals, in particular the hydroxyl radical, played a significant role of oxidizing Abeta peptides, which effectively blocked further fibrillation. The efficacy of photoelectrocatalytic inhibition on Abeta aggregation was enhanced by introducing cobalt phosphate (Co-Pi) as a co-catalyst on the hematite photoanode, which facilitated the separation of electron-hole pairs. We verified that both bare and Co-Pi@hematite photoanodes are biocompatible and effective in reducing Abeta aggregation-induced cytotoxicity.

The abnormal aggregation of extracellular beta-amyloid (Abeta) peptides is a major pathological event of Alzheimers disease. Recently, photodynamic suppression of the assembly of Abeta peptides into beta-sheet-rich aggregates and the resulting neurotoxicity were suggested; however, its application has been limited by the low tissue penetration-depth of UV or visible light. Herein, we report rose bengal (RB)-loaded upconverting nanocomposites as a NIR-responsive inhibitor of Abeta aggregation. Rattle-structured, organosilica shell (ROS) deposited on NaYF4:Yb,Er nanocrystals (UCNPs) was adopted as an efficient photosensitizer carrier with high loading capacity and disaggregation effect of RB. We demonstrated that the UCNP@ROS exhibited high energy transfer efficiency to the loaded RB under the irradiation of 980 nm NIR light and generated singlet oxygen efficiently inhibiting Abeta self-assembly. Furthermore, RB-loaded UCNP@ROS is not only biocompatible, but also effective in suppressing Abeta-induced cytotoxicity under NIR light, suggesting its potential towards photodynamic treatment of of Alzheimers disease in future.

In natural photosynthesis, solar energy is converted to chemical energy through a cascaded, photoinduced charge transfer chain that consists of primary and secondary acceptor quinones (i.e., QA and QB), which leads to exceptionally high quantum yield near unity. Inspired by the unique multistep charge transfer architecture in nature, we have synthesized catecholamine-functionalized, reduced graphene oxide (RGO) film as a redox mediator that can mimic quinone acceptors in the photosystem II. We utilized polynorepinephrine (PNE) as a redox-shuttling chemical, as well as to coat graphene oxide (GO) and to reduce GO to RGO. The two-electrons-and-two-protons-involving charge transfer characteristic of quinone ligands in PNE acted as an electron acceptor that facilitated charge transfer in photocatalytic water oxidation. Furthermore, PNE-coated RGO film promoted fast charge separation in [Ru(bpy)3]2+ and over two-fold increased the activity of cobalt phosphate on photocatalytic water oxidation. The results suggest that our bio-inspired strategy for the construction of forward charge transfer pathway can provide more opportunities to realize efficient artificial photosynthesis.

Green conversion of carbon dioxide to fuels has attracted high interest recently due to the global issues of environmental sustainability and renewable energy sources. In this study, we present photoelectrochemical (PEC) regeneration of nicotinamide cofactors (NADH) coupled with enzymatic synthesis of formate from CO2 towads mimicking natural photosynthesis. The water oxidation-driven PEC platform exhibited high yield and rate of NADH regeneration compared to many other homogeneous, photochemical systems. We successfully coupled solar-assisted NADH reduction with enzymatic CO2 reduction to formate under continuous CO2 injection.

Redox enzymes are industrially important for catalyzing highly complex reactions because of their excellent regio- and stereo-selectivity; however, broad application of redox enzymes has been often limited by the requirement of stoichiometric supply of cofactors such as β-nicotinamide adenine dinucleotide (NADH). Here, we report light-driven cofactor regeneration coupled with water oxidation by employing a photoelectrochemical cell platform consisted of a FeOOH/Fe2O3 photoanode and a black silicon photocathode. The FeOOH layer deposited on Fe2O3 surface decreased reaction barriers for water oxidation. The black silicon photocathode exhibited high photocurrent response and superior capacity to drive cofactor reduction. The cofactor regeneration yield in the photoelectrochemical cell was almost two-fold higher than that obtained in homogenous system, which demonstrates that photoelectrochemical cell is a promising platform for redox biocatalytic reactions using water as an electron donor.

We report on a silicon-based photoelectrochemical cell that integrates a formate dehydrogenase from Thiobacillus sp. (TsFDH) to convert CO2 to formate using water as an electron donor under visible light irradiation and an applied bias. Our results revealed that sequential transfer of electrons, extracted via a water oxidation reaction at a npp+ triple-junction silicon on ITO (3-jn-Si/ITO/CoPi) photoanode, to a a hydrogen-terminated silicon nanowire (H-SiNW) photocathode, and further to TsFDH, leads to effective formate production with a faradaic efficiency of 16.18% under the applied bias of 1.8 V, while no formate was synthesized directly at the H-SiNW photocathode alone. The formate yield increased significantly through the integrated PEC system, which continuously regenerated NADH for TsFDH-catalyzed CO2 reduction. Moreover, we demonstrated that our silicon-based biocatalytic system could be operated under natural sunlight using a solar tracking module, which is a highly desirable result for the practical utility of the PEC as a sustainable solar energy harvesting system. The current study suggests that the deliberate integration of biocatalysis to a PEC platform can provide an opportunity to synthesize valuable chemicals with the use of earth-abundant materials and sustainable resources. With our biocatalysis-integrated PEC platform, further engineering of enzymes and photoelectrode materials would provide more opportunity to improve efficiency of the system.

In nature, quinone plays a vital role in numerous electrochemical reactions for energy transduction and storage; such processes include respiration and photosynthesis. For example, fast proton-coupled electron transfer between primary and secondary quinones in green plants triggers the rapid charge separation of chlorophyll molecules, achieving unparalleled photosynthesis with near-unity quantum yield. In addition, quinone-rich polymers such as eumelanin and polydopamine show unique optical and electrical properties (e.g., strong broadband absorbance or a switching response to external stimuli), mostly arising from their chemically disordered structures. Understanding the unique features of quinone and its derivatives can provide solutions to the construction of bio-inspired systems for energy harvesting and conversion. This paper reviews recent advances in the design of quinone-functionalized hybrid materials based on quinones redox, electrical, optical, and metal chelating/reducing properties to determine these materials applications in energy-harvesting and -storage systems, such as artificial photosynthetic platforms, rechargeable batteries, pseudocapacitors, phototransistors, plasmonic light harvesting platforms, and dye-sensitized solar cells.

FROM WASTE TO VALUABLES: Human urine is studied as a potential source of energy for light-driven redox biocatalytic reactions. The urea-rich human urine functions as an efficient chemical fuel in a photoelectrochemical cell regenerating nicotinamide cofactor (NADH), an essential hydride mediator that is required for numerous redox biocatalytic reactions. We demonstrate the utility of human urine as a chemical fuel for driving redox biocatalysis in a photoelectrochemical cell. Ni(OH)2-modified alpha-Fe2O3 is selected as a photoanode for the oxidation of urea in human urine and black silicon (bSi) is used as a photocathode material for NADH regeneration. The electrons extracted from human urine are used for the regeneration of NADH. The catalytic reactions at both the photoanode and the photocathode were significantly enhanced by light energy that lowered the overpotential and generated high currents in the full cell system.

Graphitic carbon nitride (g-C3N4) is a metal-free material of only carbon and nitrogen-based structure called tri-s-triazine, which is non-toxic, abundant, and cost-effective. While there are only a few studies about biomedical applications of g-C3N4, good biocompatibility of g-C3N4 has been confirmed recently through its use in cancer diagnosis, drug delivery, and cell imaging. Here we report that g-C3N4 has a suppressive ability toward Alzheimers beta-amyloid (Abeta) aggregation under light illumination. Under commercial white light emitting diode light, photo-induced electrons of g-C3N4 with a 2.6 eV bandgap generated reactive oxygen species (ROS), such as superoxide anion and singlet oxygen; then, the ROS blocked further Abeta aggregation as a way of photo-oxidation, impacting the conformational structure of Abeta. Through metal doping into a g-C3N4 framework, we further demonstrated that Fe-doped g-C3N4 showed enhanced optical properties and stronger inhibition on Abeta aggregation than bare g-C3N4. Both g-C3N4 and Fe-doped g-C3N4 had negligible cytotoxicity and exhibited significant reduction in Abeta-induced cell death.

Harnessing solar energy has recently attracted much attention due to the increased importance of environmental and energy issues. In particular, the photolysis of water using photocatalysts, so called artificial photosynthesis, has been receiving great attention in terms of the direct and efficient solar energy conversion system to produce O2 and H2 as chemical fuels. The effectiveness of water splitting using photocatalysts is determined by the utilization of visible light of the solar spectrum, capacity of the harvested light to generate charge carriers, and the extent of charge separation and transfer. Thus, the selection of semiconducting photocatalyst materials with proper band position, bandgap energy, and long-lived stability is critical for the viable water splitting system. Herein we report on the synthesis of highly porous, 1-D tungsten-doped BiVO4 nanofibers (W:BiVO4 NFs). To facilitate photocatalysis, we introduced nickel nanoparticles (NiOx NPs) as co-catalysts on the surface of the W:BiVO4 NFs. The outstanding water oxidation performance of the NiOx NPs-functionalized W:BiVO4 NFs were obtained through (i) the control of polymer/precursor to achieve porous W:BiVO4 NFs (for higly increased surface area), (ii) the control of tungsten-doping level (for fast charge transfer), and (iii) the optimization of the loading amounts of NiOx NPs (for efficient charge pathway suppression of charge recombination).

In the past 50 years, cytochrome P450 monooxygenases (P450s) have been given significant attention for the synthesis of natural products (e.g., vitamins, steroids, lipids) and pharmaceuticals. Despite their potential, however, costly nicotinamide cofactors such as NAD(P)H are required as reducing equivalents; thus, in situ regeneration of NAD(P)H is essential to sustaining P450-catalyzed reactions. Furthermore, poor stability of P450s has been considered as a hurdle, hampering industrial implementations of P450-catalyzed reactions. Herein we describe the development of an economic and robust process of P450-catalyzed reactions by the combination of P450 immobilization and solar-induced NADPH regeneration. The P450 monooxygenase could be efficiently immobilized on a P(3HB) biopolymer, which enabled simple purification from the E. coli host. We clearly demonstrated that the P450-P(3HB) complex exhibited much higher enzymatic yield and stability than free P450 did against changes of pH, temperature, and concentrations of urea and ions. Using the robust P450-P(3HB) complex and solar-tracking module, we successfully conducted P450-catalyzed artificial photosynthesis under the irradiation of natural sunlight in a preparative scale (500 mL) for multiple days. To the best of our knowledge, this is the largest reactor volume in P450-catalyzed reactions reported so far. We believe that our robust platform using simple immobilization and abundant solar energy promises a significant breakthrough for the broad applications of cytochrome P450 monooxygenases.

Cellulose, a main component of green plants, is the most abundant organic chemical on Earth, produced 1011 tons per year in the biosphere. The polysaccharide consists of D-glucose units linked by beta-1,4-glycosidic bonds and has been widely utilized in diverse engineering fields because of its biocompatibility, abundance, and high chemical stability. In this work, we have demonstrated the utility of carboxymethyl cellulose (CMC) fibers as a sacrificial template to produce binary and tertiary metal oxides fibers. The electrostatic interaction between metal ions and the carboxyl groups in CMC fibers induced a hierarchical structure of metal oxides. The morphologies of synthesized metal oxides (e.g., CeO2, ZnO, and CaMn2O4) could be controlled according to synthetic conditions, such as metal precursor concentration, calcination temperature, and the amount of CMC fibers. Thus-synthesized CMC-templated metal oxide fibers exhibited enhanced performances for photocatalytic, photochemical, and electrocatalytic reactions. The CeO2 fibers showed much higher photocatalytic activity than CeO2 nanoparticles due to superior ability to generate reactive oxygen species which can degrade organic pollutants. We also demonstrated that hierarchical ZnO fibers hybridized with g-C3N4 could provide directional charge transfer pathway and showed their utility for biocatalyzed artificial photosynthesis through visible light-driven chemical NADH regeneration coupled with redox enzymatic reaction. The electrochemical properties of CaMn2O4 fibers enabled bi-functional reactions of oxygen reduction and evolution reactions. We expect that the economical and environmentally friend approach could be extended to green synthesis of hierarchically structured materials of other metal oxides.

The abnormal assembly of beta-amyloid (Abeta) peptides into neurotoxic, beta-sheet rich amyloid aggregates is a major pathological hallmark of Alzheimers disease (AD). Photodynamic therapy (PDT) is a promising strategy for treating various diseases due to its temporal and spatial controllability and reduced side effects. However, PDT for neurodegenerative diseases has not been explored yet. Here, we show that light-induced photosensitizing molecules can regulate Abeta amyloidogenesis. Our multiple photochemical analyses using circular dichroism, atomic force microscopy, dot blot, and native gel electrophoresis verified that photo-activated meso-tetra(4-sulfonatophenyl) porphyrin (TPPS) successfully inhibits Abeta aggregation in vitro. Furthermore, we demonstrate that Abeta toxicity was relieved in the photoexicited-TPPS-treated Drosophila AD model. TPPS suppresses neural cell death, synaptic toxicity, and behavioral defects in the Drosophila AD model under blue light illumination. Behavioral phenotypes, including larval locomotion defect and short lifespan caused by Abeta overexpression, were also rescued by blue light-excited TPPS.

The practical limits of coinage metal-based plasmonic materials demand sustainable, abundant alternatives with a wide plasmonic range of the solar energy spectrum. Aluminum (Al) is an emerging alternative, but its instability in aqueous environments critically limits its applicability to various light-harvesting systems. Here, we present a novel design strategy to achieve a robust platform for plasmon-enhanced light-harvesting using Al nanostructures. The incorporation of mussel-inspired polydopamine nano-layers in the Al nanoarrays allows for the reliable use of Al plasmonic resonances in a highly corrosive photocatalytic redox solution, and provides nanoscale arrangement of organic photosensitizers on Al surfaces. Resulting Al-photosensitizer core-shell assemblies exhibit plasmon-enhanced light absorption, which enables a 300% increase in photo-to-chemical conversion. Our strategy opens a path to realizing the stable and advanced use of aluminum for plasmonic light-harvesting.

Photoelectrochemical (PEC) detection is an attractive biosensing strategy because it inherits the benefits of electrochemical sensors, such as low cost, simple instrumentation and high sensitivity. Furthermore, PEC sensing can reduce undesired background noise and enhance sensitivity by using two separate forms of signals: light (for excitation) and electricity (for detection). Hematite is a promising photoanode material because of its strong absorption of visible light (Eg ~2.1 eV), high stability, low price, and environmentally benign characteristics. Here, we report the first hematite-based PEC biosensor platform to detect NADH under visible light. To enhance the electrical signal of photoanodes, we employed mussel-inspired polydopamine which immobilize redox mediators on hematite. The enzymatic PEC biosensor enabled the detection of glucose, ethanol, and lactate, and even showed successful detection of glucose in human plasma suggesting the practical usefulness of our platform.

Peptide self-assembly is an attractive route to the synthesis of intricate organic nanostructures that possess remarkable structural variety and biocompatibility. Recent studies on peptide-based, self-assembled materials have been expanding beyond the construction of high-order architectures; they are now reporting new functional materials that have applications in the emerging fields, such as artificial photosynthesis and rechargeable batteries. Nevertheless, there have been rather scarce reviews particularly concentrating on such versatile, emerging applications. Herein we selectively review recent advances in the synthesis of self-assembled peptide nanomaterials (e.g., cross beta-sheet-based amyloid nanostructures, peptide amphiphiles, etc.) and describe their new applications in diverse, interdisciplinary fields ranging from optics, energy storage/conversion to healthcare. We highlight the applications of peptide-based self-assembled materials in unconventional fields, such as photoluminescent peptide nanostructures, artificial photosynthetic peptide nanomaterials, and lithium-ion battery components. We also discuss relation of such functional materials to the rapidly progressing biomedical applications of peptide self-assembly, which include biosensors/chips and regenerative medicine. The combination of strategies shown in respective applications would further promote the discovery of novel, functional small materials.

Titanium dioxide has long been pursued as a promising material for many photocatalytic applications because of its chemical activity and stability as well as low cost. On the other hand, graphene oxide (GO) can serve as a scaffold for functional hybrid materials by interacting with various organic and inorganic chemicals. Herein, we synthesized graphene oxide-wrapped anatase TiO2 nanoparticles (GO-TiO2 NPs) as a self-adhesive photocatalyst for UV-activated colorimetric oxygen indicators. Our multiple analyses with zeta potential, UV-Vis spectrophotometry, and cyclic voltammetry revealed that methylene blue (MB), a widely used redox dye for colorimetric oxygen indication, strongly adsorbs onto GO-TiO2 NPs by both electrostatic and pi-pi stacking interactions. We successfully fabricated UV-activated visual oxygen indicator films using MB, GO-TiO2 NPs, glycerol, and hydroxyethyl cellulose (HEC) as a redox dye, a UV-absorbing self-adhesive photocatalyst, a sacrificial electron donor, and an encapsulation polymer, respectively. The chemical attraction between GO and MB significantly reduced dye leakage problem, a major drawback of conventional oxygen indicators; MB leaching from GO-TiO2-based film was 4.8 times lower than that from TiO2-based film. This novel MB/GO-TiO2/glycerol/HEC film was photobleached by UV irradiation within 6 min and regained its blue color in the air within 20 min, demonstrating its useful functionality as a UV-activated colorimetric oxygen indicator.

Cytochromes P450 (P450 or CYP) belong to a superfamily of multifunctional monooxygenases that contain heme molecules (i.e., Fe-porphyrin) as a prosthetic group. They can catalyze various oxidative metabolic reactions of endogenous and exogenous compounds in living organisms. Their catalytic diversity and vast substrate range with regio- and stereo-specificity have high potential in applications to drug metabolism as well as in the fine chemical synthesis of steroids, lipids, vitamins, and natural products. Here, we have designed a novel visible light-driven platform for cofactor-free, whole-cell P450 photo-biocatalysis using eosin Y (EY) as a photosensitizer. EY can easily enter into the cytoplasm of Escherichia coli and bind specifically to the heme domain of P450. The catalytic turnover of P450 was mediated through the direct transfer of photo-induced electrons from the photosensitized EY to the P450 heme domain under visible light illumination. The photoactivation of the P450 catalytic cycle in the absence of cofactors and redox partners is successfully conducted using many bacterial P450s (variants of P450 BM3) and human P450s (CYPs 1A1, 1A2, 1B1, 2A6, 2E1, and 3A4) for the bioconversion of different substrates, including marketed drugs (simvastatin, lovastatin, and omeprazole) and a steroid (17beta-estradiol), to demonstrate general applicability of the light-driven, cofactor-free system.

The abnormal aggregation of beta-amyloid (Abeta) peptides in the brain is a major pathological hallmark of Alzheimers disease (AD). The suppression (or alteration) of Abeta aggregation is considered to be an attractive therapeutic intervention for treating AD. We report on visible light-induced inhibition of Abeta aggregation by xanthene dyes, which are widely used as biomolecule tracers and imaging markers for live cells. Among many xanthene dyes, rose bengal (RB) under green LED illumination exhibited a much stronger inhibition effect upon photo-excitation on Abeta aggregation than RB under dark conditions. We found that RB possesses high binding affinity to Abeta; it exhibits a remarkable red shift and a strong enhancement of fluorescence emission in the presence of Abeta. Photo-excited RB interfered with an early step in the pathway of Abeta self-assembly and suppressed the conformational transition of Abeta monomers into beta-sheet-rich structures. Photo-excited RB is not only effective in the inhibition of Abeta aggregation, but also in the reduction of Abeta-induced cytotoxicity.

Cytochrome P450 monooxygenases that catalyze a remarkable variety of oxidative transformation are of exceptional interest for the synthesis of fine chemicals. However, due to their instability and the requirment of expensive cofactors, P450s have not been used extensively for industry yet. Here, we developed new platform of P450-catalyzed reaction toward preparative scale process by the immobilization of P450s on polyhydroxybutyrate granules. Using the fusion with phasin, P450s could be efficiently immobilized on P(3HB) granules in the cytoplasm of Escherichia coli, and the complex was simply purified by centrifugation after cell disruption. Under various harsh environmental conditions (pH, temperature, urea, and ionic strength), the immobilized P450s exhibited much higher stability and activity compared to those of non-immobilized P450s.

The use of biologically occurring redox centers holds a great potential in designing sustainable energy storage systems. Yet, to become practically feasible, it is critical to explore optimization strategies of biological redox compounds, along with in-depth studies regarding their underlying energy storage mechanisms. Here, we report a molecular simplification strategy to tailor the redox unit of pteridine derivatives, which are essential components of ubiquitous electron transfer proteins in nature. We first apply pteridine systems of alloxazinic structure in lithium/sodium rechargeable batteries, and unveil their reversible tautomerism during energy storage. Through the molecular tailoring, the pteridine electrodes can show outstanding performance, delivering 533 Wh kg-1 within 1 hour and 348 Wh kg-1 within 1 minute, as well as high cyclability retaining 96% of the initial capacity after 500 cycles at 10 A g-1. Our strategy combined with experimental and theoretical studies suggests guidance for the rational design of organic redox centers.

In this report, photoelectroenzymatic synthesis of chemical compounds employing platinum nanoparticle-decorated silicon nanowire (Pt-SiNW) is presented. Pt-SiNW was proved to be an efficient material for photoelectrochemical cofactor regeneration because silicon nanowire absorbs a wide range of solar spectrum and platinum nanoparticle serves as an excellent catalyst for electron and proton transfer. By integrating the platform with redox enzymatic reaction, visible light-driven electroenzymatic synthesis of L-glutamate was achieved. Compared to electrochemical and photochemical methods, this approach is free from side reactions caused by sacrificial electron donor and has advantages of applying low potential to realize energy-efficient and sustainable synthesis of chemicals by photoelectroenzymatic system.

Efficient harvesting of unlimited solar energy and its conversion into valuable chemicals is one of the ultimate goals of scientists. With the ever-increasing concerns about sustainable growth and environmental issues, numerous efforts have been made to develop artificial photosynthetic process for the production of fuels and fine chemicals mimicking natural photosynthesis. Despite the research progresses made over the decades, the technology is still in its infancy because of the difficulties in kinetic coupling of whole photocatalytic cycles. Here, we report a new type of artificial photosynthesis system that can avoid such problems by integrally coupling biocatalytic redox reactions with photocatalytic water-splitting. We found that photocatalytic water-splitting reaction can be efficiently coupled with biocatalytic redox reactions by using tetra-cobalt polyoxometalate and Rh-based organometallic compound as hole and electron scavengers, respectively, for photoexcited Ru(bpy)32+ dye. Based on these results, we could successfully photosynthesize a model chiral compound (L-glutamate) using a model redox enzyme (glutamate dehydrogenase) upon in-situ photo-regeneration of cofactors.

We report on the capability of polydopamine (PDA), a mimic of mussel adhesion proteins, as an electron gate as well as a versatile adhesive for mimicking natural photosynthesis. This work demonstrates that PDA accelerates the rate of photoinduced electron transfer from light-harvesting molecules through two-electron and two-proton redox-coupling mechanism. The introduction of PDA as a charge separator significantly increased the efficiency of photochemical water oxidation. Furthermore, simple incorporation of PDA ad-layer on the surface of conducting materials (such as carbon nanotubes) facilitated fast charge separation and oxygen evolution through the synergistic effect of PDA-mediated, proton-coupled electron transfer and substrate materials high conductivity. Our work shows that PDA is an excellent electron acceptor as well as a versatile adhesive; thus, it opens a new electron gate for harvesting photoinduced electrons and designing artificial photosynthetic systems.

Solar energy has attracted much attention because of the huge amount of energy continuously transferred from the sun to the Earth. While numerous photosensitizing systems had been studied over the decades for light harvesting, most photosensitizers possess a large bandgap (> 1.7 eV) requiring ultraviolet and visible light for their activation. Considering that over 46% of solar energy is in the near-infrared (NIR) range, almost half of overall solar spectrum cannot be utilized to activate those photosensitizers. Herein, we first report on NIR light-driven biocatalytic artificial photosynthesis using upconversion nanoparticles. Upconversion refers to nonlinear optical processes that occur through anti-Stokes emission, in which an emitted photon has more energy than the absorbed photon by sequential absorption of photons. For NIR light-driven photoenzymatic synthesis, we synthesized silica-coated upconversion nanoparticles, such as Si-NaYF4:Yb,Er and Si-NaYF4:Yb,Tm, for efficient photon-conversion through Forster resonance energy transfer (FRET) with rose bengal (RB), a photosensitizer. We observed NIR-induced electron transfer using linear sweep voltammetric analysis, which indicated photoexcited electrons of RB/Si-NaYF4:Yb,Er were transferred to NAD+ through a Rh-based electron mediator. RB/Si-NaYF4:Yb,Er nanoparticles, which exhibited higher FRET efficiency due to more spectral overlap than RB/Si-NaYF4:Yb, resulted in much better performance for photoenzymatic conversion. Our work shows that upconversion nanoparticles with anti-Stokes emission are promising light harvesters for versatile usage of NIR light in solar-to-chemical conversion processes.

We present a simple and versatile approach for the construction of plasmonic metal/ photosensitizer core-shell nanohybrids for efficient light harvesting by adopting multi-purpose polydopamine (PDA) nanolayers inspired by mussel adhesion. In our plasmonic core-shell assembly, PDA coating plays multiple roles: (1) a reducing agent for the synthesis of metal nanoparticles, (2) a scaffold for the encapsulation of photosensitizing dye molecules, and (3) an adhesive layer between the nanohybrid and the substrate. In contrast to nanolithography processes, the entire synthetic procedure can be handled in an aqueous solution under mild conditions and requires no intricate equipment, which confers advantages in large-scale production. Also, by virtue of the remarkable adhesive versatility of PDA coating, this approach can be applied to the development of elaborate core-shell nanostructures regardless of material type and morphology of substrates. We found that the resulting plasmonic nanohybrids exhibit strongly enhanced photocatalytic activity during visible light-induced artificial photosynthesis as a result of amplified light absorption by molecular photosensitizers through LSPR from the plasmonic metal nanoparticles. We expect that a diverse range of metal core (e.g., gold and silver) and dye molecule combinations are possible through the use of our strategy to facilitate the synthesis of assorted sets of nanohybrids with desired optical properties, allowing design flexibility in solar energy conversion applications.

Bio-inspired organic electrodes that imitate natural energy metabolisms, such as respiration and photosynthesis, can facilitate the design of sustainable batteries. For example, the electro-active carbonyl compounds mimicking biological quinone cofactors that can be obtained from biomass through eco-friendly processes are intriguing candidates for such electrode materials. Also, flavin-based electrodes that function through the imitation of the cellular energy transduction mechanism are promising candidates. The practical use of organic-based electrodes, however, suffers from sluggish kinetics and poor capacity retention, which originate from low electronic conductivity and dissolution of electroactive compounds into electrolytes. Here, we report a novel and facile design strategy for organic electrodes to achieve high energy and power densities combined with excellent cyclic stability. Non-covalent nanohybridization of electroactive aromatic molecules with single-walled carbon nanotubes (SWNTs) by exploiting pi-pi interactions leads to a rearrangement of electroactive molecules from bulk crystalline particles into molecular layers on conductive scaffolds. The nanohybrid electrode in the form of a flexible, free-standing paper (free of binder/additive and current collector) results in ultrafast kinetics delivering 510 Wh/kg within 30 minutes (204 mAh/g ~ 98% of theoretical capacity) and 272 Wh/kg of energy even within 46 seconds. Moreover, the stable anchorage of electroactive molecules on SWNTs enables above 99% capacity retention upon 100 cycles, which was hardly achieved for organic electrodes. Our approach can be extended to other aromatic organic electrode systems, bringing organic redox chemicals a step closer to practical cathodes in rechargeable batteries.

Solar-driven water oxidation is an essential way to provide electrons for artificial photosynthesis. IrO2 colloids have been used as one of highly-efficient water oxidation catalysts due to their distinguished catalytic activity for water oxidation. However, IrO2 nanoparticles (NPs), which posses a hydrous nature, often suffer from corrosive surface degradation and enter into unstable Ir oxidation states, thereby limiting their cycling characteristics. In this work, we propose a new water oxidation catalyst for enhanced oxygen evolution and long-term recyclability through the functionalization of highly crystalline IrO2 NPs on semiconducting TiO2 nanofibers (NFs). The effects of IrO2 NPs immobilized on TiO2 NFs were investigated in terms of decoration position (inner and outer layers of NFs), crystallite size (10 nm and 30 nm), and loading amount (0 - 5.17 wt %). IrO2 (10 nm)-decorated TiO2 NFs exhibited a high turnover number (TON: 322) and superior recyclability for repeated water oxidation (90% O2 evolving capability after 10 cycles). X-ray photoelectron spectroscopy analysis verified that TiO2 NFs anchored to discrete IrO2 NPs can maintain the oxidation state of IrO2 by self-reduction of TiO2 scaffold. Our synthetic strategy offer a promising route for fabricating efficient and robust catalyst via immobilization of crystalline water oxidation catalysts on semiconducting metal-oxide scaffold.

We introduce shell cross-linked nanocapsules as an efficient tumor-targeted systemic delivery nanocarrier for highly luminescent, heavy-metal-free Cu0.3InS2/ZnS (CIS/ZnS) core-shell quantum dots (QDs). The CIS/ZnS QDs are synthesized by using a hot injection method with copper iodide, indium acetate, zinc stearate, and dodecanethiol. A mixture of the prepared QDs and amine-reactive six-armed poly(ethylene glycol) (PEG) in dichloromethane was emulsified into an aqueous solution containing human serum albumin (HSA). The resulting shell cross-linked nanocapsules show excellent dispersion stability in a serum-containing medium and high luminescence comparable to QDs in a non-polar organic solvent. Folic acid is introduced as a tumor-targeting ligand. In vivo tumor targeted delivery is demonstrated by measuring the fluorescence intensity of several major organs and tumor tissue after an intravenous tail vein injection of the nanocapsules into nude mice. The cytotoxicity of the QD-loaded HSA-PEG nanocapsules is also examined in several 32 types of cells. Our results show that the cellular uptake of the QDs is critical for cytotoxicity. Moreover, a significantly lower level of cell death is observed in the CIS/ZnS QDs compared to nanocapsules loaded with cadmium-based QDs. This study suggests that the systemic tumor targeting of heavy metal-free QDs using shell cross-linked HSA-PEG hybrid nanocapsules is a promising route for in vivo tumor diagnosis with reduced non-specific toxicity

Natural photosynthesis, a solar-to-chemical energy conversion process, occurs through a series of photo-induced electron transfer reactions in nanoscale architectures that contain light-harvesting complexes, protein-metal clusters, and many redox biocatalysts. Artificial photosynthesis in nanobiocatalytic assemblies aims to reconstruct man-made photosensitizers, electron mediators, electron donors, and redox enzymes for solar synthesis of valuable chemicals through visible light-driven cofactor regeneration. The key requirement in the design of biocatalyzed artificial photosynthetic process is an efficient and forward electron transfer between each photosynthetic component. This review introduces recent research outcomes in the development of nanobiocatalytic assemblies that can mimic natural photosystems I and II, respectively. Current issues in biocatalytic artificial photosynthesis and future perspectives are discussed.

The self-assembly of peptide-based building blocks is an attractive route for fabricating functional materials due to their unique features, such as functional flexibility and molecular recognition as well as environmental compatibility. Here, we report on the development of artificial light-harvesting hydrogel generated by the self-assembly of Fmoc-FF peptides and metalloporphyrins. We utilized the self-assembled peptide nanostructure of Fmoc-FF as a template to assemble metalloporphyrins into efficient light- harvesting antenna. The metalloporphyrins were placed in close enough proximity to each other to enable excited energy transfer, increasing the photosensitization efficiency, as observed in natural light-harvesting complexes in green plants. The metalloporphyrins in the light-harvesting hydrogel increased the efficiency of photocatalytic water oxidation by iridium oxide nanoparticles up to about 3.7 times compared to their physical mixture. The peptide-based platform could further extend possible sets of functional molecules simply by adding or modifying amino acids in the motif peptides. Scientific insights into the effects of nanoscale-assembled structures of photosensitizers on excited energy transfer can broaden the potential application of biomimetic approaches for light-driven energy systems and photosensitive sensor devices.

Artificial photosynthesis is an attractive way to utilize solar energy through inspiration from natural photosynthesis in green plants. Water-splitting is critically required to establish an artificial photosynthetic system that consists of sequential charge-obtaining and transferring reactions. The oxidation of water is a limiting step to achieving water-splitting because of its multi-hole-related characteristics. A key to the development of effective water oxidation catalysts is the optimized control of material structure and composition through a facile synthetic method. This work synthesized polycrystalline RuO2/Co3O4 core/shell nanofibers by electrospinning and evaluated their photocatalytic water oxidation performance using a Ru(bpy)32+/persulfate system under visible light illumination. Our results show that RuO2/Co3O4 nanofibers exhibit significantly enhanced efficiency of photocatalytic water oxidation with a higher number of turnover frequency than those of pristine Co3O4 nanoparticles, Co3O4 nanofibers, and RuO2 nanofibers, respectively. The unique core-shell structure of RuO2/Co3O4 nanofibers comprising the inner region of highly conductive RuO2 and the outer region of catalytic Co3O4 provided a fast and effective transport highway for holes to O2-evolving sites. This work highlights the potential of tailored 1D binary composite nanofibers for the development of efficient oxygen-evolving catalysts and offers a new viewpoint for exploring multi-component catalysts through electrospinning.

Cellular metabolism comprises energy transduction machineries that operate by a series of redox-active components to store energies from nutrients, which are transduced into high-energy intermediates for cellular works such as chemical synthesis, transport, and movement. Biological energy transduction mechanism hints at the construction of a man-made energy storage system. Herein, we present a bio-inspired strategy to design high-performance energy devices based on the analogy between energy storage phenomena of mitochondria and lithium rechargeable batteries. Flavins, a key redox element in respiration and photosynthesis, facilitate either one- or two-electron-transfer redox processes accompanying proton transfer at nitrogen atoms of diazabutadiene motif during cellular metabolism. We have successfully demonstrated flavins as a molecularly tunable cathode material that exhibits reversible reactivity with two lithium ions and electrons per formula unit. Analysis of both the ex situ characterizations and density-functional theory (DFT)-based calculations revealed that the redox reaction occurs via two successive single-electron transfer steps, which is analogous to the proton-coupled electron transfer mechanism of flavoenzymes. Tailored flavin analogues obtained via chemical substitution on the isoalloxazine ring showed fine tunability of electrochemical properties, exhibiting a gravimetric capacity of 174 mAh/g and an average redox potential of 2.65 V, and its expected energy density is comparable to that of LiFePO4.

The control of cell-material interaction is a key issue in the design of suitable scaffold materials for tissue engineering because the physicochemical properties (e.g., surface chemistry, topography) of substrate materials significantly influence cell behaviors. We studied the effect of mussel-inspired polydopamine (PDA) functionalization of the substrate surface in combination with topographical cues on the behavior of skeletal myoblasts. The formation of the PDA ad-layer on the scaffold surface was analyzed using multiple tools including atomic force microscopy, scanning electron microscopy, and Raman spectroscopy. When myoblasts were grown on planar glass substrates, the PDA ad-layer well-supported the adhesion and proliferation of myoblasts, and enhanced the differentiation of myoblasts into multinucleate myotubes. We further developed well-aligned nanofibrous scaffolds to resemble the highly ordered architectures of skeletal muscle tissues, followed by PDA-based surface functionalization. On PDA-modified nanofibers, myogenic protein expression and the fusion of myoblasts were increased significantly compared with those on unmodified nanofibers. The multinucleate myotubes on the aligned nanofibers were oriented in a direction parallel to the nanofibers. Our results suggest that the combination of mussel-inspired surface functionalization and uniaxial topography is a useful strategy for scaffold design in skeletal tissue engineering.

Solar energy utilization is accomplished in green plants through a cascade of photo-induced electron transfer, which remains a target model for realizing artificial photosynthesis. In this article, we introduce the concept of about how to design biocatalyzed artificial photosynthesis through coupling redox biocatalysis and photocatalysis to mimic natural photosynthesis. Key design principles for reaction components, such as electron donors, photosensitizers, and electron mediators, are described for artificial photosynthesis involving biocatalytic assemblies. Recent research outcomes that serve as a proof of the concept are summarized and current issues are discussed to provide a future perspective.

We report the synthesis of a 3D-structured graphene/Rh-complex hydrogel that works as a robust catalyst for electroenzymatic reactions. Pyridine nucleotide cofactors [NAD(P)H] are critically required as a reducing power for many reactions catalyzed by redox enzymes. Thus, in-situ regeneration of reduced cofactors is essential to ensuring redox enzymes continue their turnover. We successfully designed the graphene/Rh-complex hydrogel by immobilizing Rh complex, an organometallic mediator, in the network of graphene hydrogel having large surface area and high conductivity. The pi-electron system in the aromatic heterocyclic region of Rh complex played a critical role in the immobilization and stabilization of Rh complex in the graphene hydrogel for electrochemical NADH regeneration. The catalytic activity of graphene/Rh-complex that has phenanthroline as a ligand remained almost the same through repeated tests. When a-ketoglutarate was electroenzymatically converted to L-glutamate in the presence of graphene/Rh-complex hydrogel, L-glutamate yield increased more than 10 times than that of free Rh complex. This work demonstrates that graphene hydrogel can boost industrially important reactions catalyzed by redox enzymes.

Graphene-based nanomaterials have received much attention in biomedical applications for drug/gene delivery, cancer therapy, imaging, and tissue engineering. Despite the capacity of 2D carbon materials as a nontoxic and implantable platform, their effect on myogenic differentiation has been rarely studied. We investigated the myotube formation on graphene-based nanomaterials, particularly graphene oxide (GO) and reduced graphene oxide (rGO). GO sheets were immobilized on amine-modified glass to prepare GO-modified glass, which was further reduced by hydrazine treatment for the synthesis of rGO-modified substrate. We studied the behavior, including adhesion, proliferation, and differentiation, of mouse myoblast C2C12 on unmodified, GO-, and rGO-modified glass substrates. According to our analyses of myogenic protein expression, multi-nucleated myotube formation, and expression of differentiation-specific genes (MyoD, Myogenin, Troponin T, and MHC), myogenic differentiation was remarkably enhanced on GO, which resulted from serum protein adsorption and nanotopographical cues. Our results demonstrate the ability of GO to stimulate myogenic differentiation, showing a potential for skeletal tissue engineering applications.

Ceria attracted much attention due to its unique redox properties and high reactivity, which has been widely applied for solid oxide fuel cells, catalysis, and sensors. However, the use of ceria as a photocatalyst is limited due to its large optical bandgap (3.19 eV). In this study, we successfully synthesized ceria sheets that exhibited distinct polycrystalline sheet-like structure with grains, the size of which varied with calcination temperatures. The grain size of ceria sheets influenced the concentration of cerium ions on their surface, thus affecting their bandgap. The nano-grained ceria sheets exhibited a red-shift in the UV-visible absorption spectrum and a much narrower bandgap (2.71-2.83 eV). Visible light-responsive photocatalytic activity was observed with nano-grained ceria sheets at a rate constant that was much higher than that of ceria nanoparticles.

Carbon-based nanomaterials such as graphene sheets and carbon nanotubes possess unique mechanical, electrical, and optical properties that present new opportunities for tissue engineering, a key field for the development of biological alternatives that repair or replace whole or a portion of tissue. Carbon nanomaterials can also provide a similar micro-environment as like a biological extracellular matrix in terms of chemical composition and physical structure, making them a potential candidate for the development of artificial scaffolds. In this review, we summarize recent research advances in the effects of carbon nanomaterial-based substrates on cellular behaviors, including cell adhesion, proliferation, and differentiation into osteo- or neural- lineages. The development of 3D scaffolds based on carbon nanomaterials (or their composites with polymers and inorganic components) is introduced, and the potential of these constructs in tissue engineering, including toxicity issues, is discussed. Future perspectives and emerging challenges are also highlighted.

Cytochrome P450 monooxygenases are multi-functional biocatalyst with potential applications in chemoenzymatic synthesis of complex chemicals as well as in studies of metabolism and xenobiotics. Widespread application of cytochrome P450s, however, is encumbered by the critical need for redox equivalents in their catalytic function. To overcome this limitation, we studied visible light-driven regeneration of NADPH for P450-catalyzed O-dealkylation reaction; we used eosin Y as a photosensitizing dye, triethanolamine as an electron donor, and Cp*Rh(bpy)H2O as an electron mediator. We analyzed catalytic activity of cell-free synthesized P450 BM3 monooxygenase variant (Y51F/F87A, BM3m2) in the presence of key components for NADPH photoregeneration. The P450-catalyzed O-dealkylation reaction sustainably maintained its turnover with the continuous supply of photoregenerated NADPH. Visible light- driven, non-enzymatic NADPH regeneration provides a new route for efficient, sustainable utilization of P450 monooxygenases.

Biomineralization, the natural pathway of assembling biogenic inorganic compounds, inspires us to exploit unique, effective strategies to fabricate functional materials with intricate structures. In this article, we review the recent advances in bio-inspired synthesis of minerals, mainly those of calcium-based minerals, and its applications to the design of functional materials for energy, environment, and biomedical fields. Biomimetic mineralization is extending its application range to unconventional area such as the design of component materials for lithium-ion batteries and elaborately structured composite materials utilizing carbon dioxide gas. Materials with highly enhanced mechanical properties are synthesized through emulating the nacre structure. Studies of bioactive minerals-carbon hybrid materials show an expansion of potential applications to fields ranging from interdisciplinary science to practical engineering such as the fabrication of reinforced bone-implantable materials.

Silicon nanowires have been widely used in many nanoscale devices, including solar cells, photoelectro- chemical cells, transistors, and battery electrodes. Herein, we report a new possible application of hydrogen- terminated silicon nanowires (H-SiNWs) as a rechargeable template for hydride transfer in redox biocatalysis. Redox enzymes can catalyze various types of complex organic synthesis under mild conditions but often require a stoichiometric amount of expensive nicotinamide cofactors (NADH) for their catalytic activities. We found that H-SiNWs transfer hydride efficiently to regenerate NADH from NAD+ via an Rh-based electron mediator. During the regeneration of NADH, the Si-Hx bonds on H-SiNWs were oxidized to form Si-OH and Si-O-Si bonds on the nanowire surface and evolve hydrogen. The oxidized H-SiNWs were readily recharged by treatment in a diluted HF solution for the repeated generation of NADH and continuous enzymatic reactions for the synthesis of D-lactate from pyruvate catalyzed by lactate dehydrogenase.

This study successfully demonstrates that hydrogen-terminated silicon nanowires (H-SiNWs) are an ideal artificial photosynthetic material, which possesses suitable photocatalytic properties to regenerate reducing power (i.e., NADH) and synthesize chemicals by photoenzymatic reaction. H-SiNWs, fabricated by a metal-assisted chemical etching process, possessed an enlarged band gap from the effect of quantum confinement and enabled a cascading electron transfer from electron donor to NAD via an Rh-based electron mediator. Approximately 80% of NADH was photo-regenerated from NAD by H-SiNWs within 2 hrs of light irradiation (wavelength > 420 nm), which was successfully coupled with the photoenzymatic synthesis of L-glutamate. Our work suggests that H-SiNWs are an ideal artificial photosynthetic material, which possesses suitable photocatalytic properties to regenerate NADH and synthesize chemicals by photoenzymatic reaction.

CuO possesses high theoretical capacity and safety with low cost and limited environmental toxicity, but a large volumetric change of CuO electrodes during the insertion and extraction of lithium ions can destroy its crystal structure and cause capacity decay in a short time. According to the present work, graphene-wrapped CuO hybrid material can highly enhance the stability and recyclability of CuO anode for lithium ion batteries. We successfully synthesized nanostructured graphene/CuO by converting a carbon dioxide-mineralized graphene oxide/calcium carbonate precursor to Cu-based minerals. Graphene/CuO exhibited nanoribbon-like CuO aggregates well-hybridized with graphene nanosheets. The excellent electrochemical performance of graphene/CuO is attributed to the synergic effect of CuO wrapped by highly conductive graphene sheets and graphene itself capable of Li-ion storage. Furthermore, flexible graphene sheets hybridized with CuO were beneficial for reducing the strain caused by volume changes during the charge/discharge process to show good cyclic performance. The synthesis of graphene/CuO and its application to lithium ion battery electrodes suggest a new possibility for hybridizing graphene and metal oxide nanoparticles using the inspiration of natural mineralization.

A graphene oxide (GO)-based immunosensor is developed for the detection of interleukin-5 (IL-5), a key cytokine associated with asthma pathology and eosinophilia. The immunosensing platform utilizes innate fluorescence of GO, not demanding biomolecules labeled with fluorescent dyes. For the construction of GO-based immunosensors, anti-IL-5 antibodies were immobilized on GO surface, then IL-5 and horseradish peroxidase (HRP)-linked antibody conjugates were consequently introduced to form a sandwich immune-complex on GO, which was investigated by using multiple analytical tools such as UV/Vis absorption, fluorescence, Raman spectroscopies, and atomic force microscopy. We found that HRP-catalyzed polymerization of 3,3-diaminobenzidine directly quenched the fluorescence of GO. The degree of GO fluorescence quenching was closely correlated to the concentration of IL-5 with a detection limit of approximately 4 pg/ml. The GO-based immunoassay system exhibited high specificity for IL-5 among other cytokines and was not affected by non-specific proteins in human serum.

The interactions between cells and materials play critical roles in the success of new scaffolds for tissue engineering, since chemical and physical properties of biomaterials regulate cell adhesion, proliferation, migration, and differentiation. We have developed nanofibrous substrates that possess both topographical cues and electroactivity. The nanofiber scaffolds were fabricated through the electrospinning of polycaprolactone (PCL, a biodegradable polymer) and polyaniline (PANi, a conducting polymer) blends. We investigated the ways in which those properties influenced myoblast behaviors. Neither nanofiber alignment nor PANi concentration influenced cell growth and proliferation, but cell morphology changed significantly from multipolar to bipolar with the anisotropy of nanofibers. According to our analyses of myosin heavy chain expression, multinucleate myotube formation, and the expression of differentiation-specific genes (myogenin, troponin T, MHC), the differentiation of myoblasts on PCL/PANi nanofibers was strongly dependent on both nanofiber alignment and PANi concentration. Our results suggest that topographical cues and the electroactivity of nanofibers synergistically stimulate muscle cell differentiation to make PCL/PANi nanofibers a suitable scaffold material for skeletal tissue engineering.

For the past decades, biomaterials have been extensively studied mostly for medical applications, such as new pharmaceuticals, tissue engineering, and artificial organs, due to their excellent biocompatibilities. Nowadays, biomaterials further expand their boundaries to various functionalities in sensor, display, and energy devices. With the move towards the use of greener materials to power vehicles, environmentally-benign synthesis of energy materials is becoming an important aspect. Here, energy storage capability of Cu-based biomineral, copper oxychloride, from the jaws of Glycera dibranchiate, a marine bloodworm, is demonstrated. Copper oxychloride electrode delivered approximately 500 mAh/g with a reasonably good cycling through the conversion reaction. This study demonstrates that inorganic biominerals, which are in-vivo synthesizable, can be utilized as energy storage materials, and furthermore, suggests the applicability of sustainable production of energy devices from bio-factory. While we have examined the Cu-based biomineral in this study, there are various natural biominerals containing other transition metal ions, such as Fe and Mn, which can serve as excellent redox elements. Therefore, significant unexplored opportunities exist in natural biominerals with different electrochemical properties.

We describe on the successful coupling of photochemical NADH regeneration with redox enzymatic synthesis by using proflavine as a light-harvesting molecule. Proflavine, a promising photosensitizer, exhibited a high capacity to drive the reduction of NAD into NADH in the presence of a Rh-based electron mediator, and the photoregenerated NADH was enzymatically active to be oxidized by NADH-dependent L-glutamate dehydrogenase for the synthesis of L-glutamate. Both the wavelength and intensity of incident light were found to significantly affect the efficiency of photochemical NADH regeneration. In contrast to proflavine, flavin derivatives, such as FAD, FMN, lumichrome, and riboflavin, accelerated solely the rate of NADH oxidation, not that of NAD reduction. Our results indicate that proflavine has the potential to become an efficient light harvesting component in biocatalytic photosynthesis driven by solar energy.

We first report on chemiluminescence resonance energy transfer (CRET) between graphene nanosheets and chemiluminescent donors. In contrast to fluorescence resonance energy transfer, CRET occurs via non-radiative dipole-dipole transfer of energy from a chemiluminescent donor to a suitable acceptor molecule without an external excitation source. We designed a graphene-based CRET platform for homogenous immunoassay of C-reactive protein, a key marker for human inflammation and cardiovascular diseases, using a luminol/hydrogen peroxide chemiluminescence (CL) reaction catalysed by horseradish peroxidase. According to our results, anti-CRP antibody conjugated to graphene nanosheets enabled the capture of CRP at the concentration above 1.6 ng/mL. In the CRET platform, graphene played a key role as an energy acceptor, which was more efficiently than graphene oxide, while luminol served as a donor to graphene, triggering the CRET phenomenon between luminol and graphene. The graphene-based CRET platform was successfully applied to the detection of CRP in human serum samples in the range observed during acute inflammatory stress.

Enzymes have long been successfully employed as biocatalysts in organic synthesis because they possess high specificity and catalytic activity even under mild conditions. However, the applications of redox enzymes were limited, mainly because of their strict requirement of reduced nicotinamide coenzyme (i.e., NADH). For the first time, employment of NAD analogs has overcome the limitations of NAD through photochemical regeneration. We investigated four different NAD analogs (i.e., APAD, PAAD, TNAD, and NAAD) that possess substituted functional groups in their pyridine part and exhibit different spectral and redox properties from NAD. We found that APAD and PAAD were photochemically reduced more efficiently than NAD, while their reduced products showed coenzyme activity comparable to natural NAD. In contrast, TNAD formed a complex with photosensitizer, and NAAD possessed more negative reduction peak potential and a negative charge, making both TNAD and NAAD poorer than NAD in photoregeneration. The higher reduction efficiency of APAD significantly enhanced the yield of redox reaction coupled with in situ visible light-driven coenzyme regeneration. Our work shows that NAD analogs can be excellent coenzymes to be regenerated via photochemical regeneration method and to be applied to redox enzymatic reactions.

Titanium dioxide, an oxide semiconductor, is regarded as a suitable material for various photocatalytic applications because of its strong oxidizing power, high chemical inertness, low cost, and long-term stability. However, a large band gap (3.2 eV) of anatase titanium dioxide restricts its use only to the narrow light-response range of ultraviolet (only 3~5% of total sunlight). We report on the synthesis of novel graphene-wrapped anatase titanium dioxide nanoparticles (NPs) that highly enhance the photocatalytic activity of titanium dioxide under visible light irradiation. We have prepared graphene-anatase titanium dioxide hybrid NPs by wrapping amorphous titanium dioxide NPs with graphene oxide (GO), followed by a one-step GO reduction and titanium dioxidecrystallization via hydrothermal treatment. Graphene-titanium dioxide NPs exhibited a red shift of the band edge and a significant reduction of the band gap (2.80 eV). We found that graphene-titanium dioxide NPs possess excellent photocatalytic property under visible light for the degradation of methylene blue with a rate constant of 0.0341/min, which was much higher than those of other titanium dioxide- based photocatalytic materials. The strategy presented in this study will enable a ready integration of functional semiconductor NPs and graphene nanosheets for the synthesis of highly photoactive graphene-based metal oxide hybrid materials.

Self-assembled light-harvesting peptide nanotubes are synthesized for artificial photosynthesis. Light-harvesting by natural photosynthesis occurs by means of two large protein complexes called photosystem I and II, which are composed of light-harvesting antenna (i.e., chlorophyll a and b) and catalytic metal clusters embedded within proteins. We have succeeded in the development of light-harvesting peptide nanotubes that integrate photosynthetic units, thus mimicking natural photosynthesis. Light-harvesting peptide nanotubes were synthesized by the self-assembly of diphenylalanine (Phe-Phe, FF) and porphyrin. We found that the J-aggregation of porphyrin occurs during the self-assembly of the FF nanotubes via electrostatic attraction and hydrogen bonding. The light-harvesting peptide nanotubes were suitable for mimicking photosynthesis because of their structure and electrochemical properties similar to natural photosystem. We demonstrated that the integrated photocatalytic system is effective for visible light-driven NADH regeneration coupled with redox enzymatic synthesis of fine chemicals such as L-glutamate.