Orientation and Incorporation of Photosystem I in Bioelectronics Devices Enabled by Phage Display

Interfacing proteins with electrode surfaces is important for the field of bioelectronics. Here, a general concept based on phage display is presented to evolve small peptide binders for immobilizing and orienting large protein complexes on semiconducting substrates. Employing this method, photosystem I is incorporated into solid‐state biophotovoltaic cells

Plasmon-Enhanced Photocurrent of Photosynthetic Pigment Proteins on Nanoporous Silver

In a quest to fabricate novel solar energy materials, the high quantum efficiency and long charge separated states of photosynthetic pigment-proteins are being exploited through their direct incorporation in bioelectronic devices. In this work, a biohybrid photocathode comprised of bacterial reaction center-light harvesting 1 (RC-LH1) complexes self-assembled on a nanostructured silver substrate yields a peak photocurrent of 166 μA cm-2 under 1 sun illumination, and a maximum of 416 μA cm-2 under 4 suns, the highest reported to date on a bare metal electrode. A 2.5-fold plasmonic enhancement of light absorption per RC-LH1 complex is observed on the rough silver substrate. This plasmonic interaction is assessed using confocal fluorescence microscopy, revealing an increase of fluorescence yield, and radiative rate of the RC-LH1 complexes, signatures of plasmon-enhanced fluorescence. Nanostructuring of the silver substrate also enhanced the stability of the protein under continuous illumination by almost an order of magnitude relative to a nonstructured bulk silver control. Due to its ease of construction, increased protein loading capacity, stability, and more efficient use of light, this hybrid material is an excellent candidate for further development of plasmon-enhanced biosensors and biophotovoltaic devices

On the mechanism of ubiquinone mediated photocurrent generation by a reaction center based photocathode

Upon photoexcitation, the reaction center (RC) pigment-proteins that facilitate natural photosynthesis achieve a metastable separation of electrical charge among the embedded cofactors. Because of the high quantum efficiency of this process, there is a growing interest in their incorporation into biohybrid materials for solar energy conversion, bioelectronics and biosensing. Multiple bioelectrochemical studies have shown that reaction centers from various photosynthetic organisms can be interfaced with diverse electrode materials for the generation of photocurrents, but many mechanistic aspects of native protein functionality in a non-native environment is unknown. In vivo, RC's catalyse ubiquinone-10 reduction, protonation and exchange with other lipid phase ubiquinone-10s via protein-controlled spatial orientation and protein rearrangement. In contrast, the mechanism of ubiquinone-0 reduction, used to facilitate fast RC turnover in an aqueous photoelectrochemical cell (PEC), may not proceed via the same pathway as the native cofactor. In this report we show truncation of the native isoprene tail results in larger RC turnover rates in a PEC despite the removal of the tail's purported role of ubiquinone headgroup orientation and binding. Through the use of reaction centers with single or double mutations, we also show the extent to which two-electron/two-proton ubiquinone chemistry that operates in vivo also underpins the ubiquinone-0 reduction by surface-adsorbed RCs in a PEC. This reveals that only the ubiquinone headgroup is critical to the fast turnover of the RC in a PEC and provides insight into design principles for the development of new biophotovoltaic cells and biosensors

Competing charge transfer pathways at the photosystem II-electrode interface.

The integration of the water-oxidation enzyme photosystem II (PSII) into electrodes allows the electrons extracted from water oxidation to be harnessed for enzyme characterization and to drive novel endergonic reactions. However, PSII continues to underperform in integrated photoelectrochemical systems despite extensive optimization efforts. Here we carried out protein-film photoelectrochemistry using spinach and Thermosynechococcus elongatus PSII, and we identified a competing charge transfer pathway at the enzyme-electrode interface that short-circuits the known water-oxidation pathway. This undesirable pathway occurs as a result of photo-induced O2 reduction occurring at the chlorophyll pigments and is promoted by the embedment of PSII in an electron-conducting fullerene matrix, a common strategy for enzyme immobilization. Anaerobicity helps to recover the PSII photoresponse and unmasks the onset potentials relating to the QA/QB charge transfer process. These findings impart a fuller understanding of the charge transfer pathways within PSII and at photosystem-electrode interfaces, which will lead to more rational design of pigment-containing photoelectrodes in general.This work was supported by the U.K. Engineering and Physical Sciences Research Council (EP/H00338X/2 to E. Reisner), the U.K. Biology and Biotechnological Sciences Research Council (BB/K010220/1 to E. Reisner), a Marie Curie International Incoming Fellowship (PIIF-GA-2012-328085 RPSII to J.J.Z.). N.P. was supported by the Winton Fund for the Physics of Sustainability. E. Romero. and R.v.G. were supported by the VU University Amsterdam, the Laserlab-Europe Consortium, the TOP grant (700.58.305) from the Foundation of Chemical Sciences part of NWO, the Advanced Investigator grant (267333, PHOTPROT) from the European Research Council, and the EU FP7 project PAPETS (GA 323901). R.v.G. gratefully acknowledges his `Academy Professor' grant from the Royal Netherlands Academy of Arts and Sciences (KNAW). We would also like to thank Miss Katharina Brinkert and Prof A. William Rutherford for a sample of T. elongatus PSII, and H. v. Roon for preparation of the spinach PSII samples

Challenges and perspectives in continuous glucose monitoring

Diabetes is a global epidemic that threatens the health and well-being of hundreds of millions of people. The first step in patient treatment is to monitor glucose levels. Currently this is most commonly done using enzymatic strips. This approach suffers from several limitations, namely it requires a blood sample and is therefore invasive, the quality and the stability of the enzymatic strips vary widely, and the patient is burdened by performing the measurement themselves. This results in dangerous fluctuations in glucose levels often going undetected. There is currently intense research towards new approaches in glucose detection that would enable non-invasive continuous glucose monitoring (CGM). In this review, we explore the state-of-the-art in glucose detection technologies. In particular, we focus on the physical mechanisms behind different approaches, and how these influence and determine the accuracy and reliability of glucose detection. We begin by reviewing the basic physical and chemical properties of the glucose molecule. Although these play a central role in detection, especially the anomeric ratio, they are surprisingly often overlooked in the literature. We then review state-of-the art and emerging detection methods. Finally, we survey the current market for glucometers. Recent results show that past challenges in glucose detection are now being overcome, thereby enabling the development of smart wearable devices for non-invasive continuous glucose monitoring. These new directions in glucose detection have enormous potential to improve the quality of life of millions of diabetics, as well as offer insight into the development, treatment and even prevention of the disease

Electrochemical Glucose Sensors—Developments Using Electrostatic Assembly and Carbon Nanotubes for Biosensor Construction

In 1962, Clark and Lyons proposed incorporating the enzyme glucose oxidase in the construction of an electrochemical sensor for glucose in blood plasma. In their application, Clark and Lyons describe an electrode in which a membrane permeable to glucose traps a small volume of solution containing the enzyme adjacent to a pH electrode, and the presence of glucose is detected by the change in the electrode potential that occurs when glucose reacts with the enzyme in this volume of solution. Although described nearly 50 years ago, this seminal development provides the general structure for constructing electrochemical glucose sensors that is still used today. Despite the maturity of the field, new developments that explore solutions to the fundamental limitations of electrochemical glucose sensors continue to emerge. Here we discuss two developments of the last 15 years; confining the enzyme and a redox mediator to a very thin molecular films at electrode surfaces by electrostatic assembly, and the use of electrodes modified by carbon nanotubes (CNTs) to leverage the electrocatalytic effect of the CNTs to reduce the oxidation overpotential of the electrode reaction or for the direct electron transport to the enzyme

Materials for Diabetes Therapeutics

This review is focused on the materials and methods used to fabricate closed-loop systems for type 1 diabetes therapy. Herein, we give a brief overview of current methods used for patient care and discuss two types of possible treatments and the materials used for these therapies–(i) artificial pancreases, comprised of insulin producing cells embedded in a polymeric biomaterial, and (ii) totally synthetic pancreases formulated by integrating continuous glucose monitors with controlled insulin release through degradable polymers and glucose-responsive polymer systems. Both the artificial and the completely synthetic pancreas have two major design requirements: the device must be both biocompatible and be permeable to small molecules and proteins, such as insulin. Several polymers and fabrication methods of artificial pancreases are discussed: microencapsulation, conformal coatings, and planar sheets. We also review the two components of a completely synthetic pancreas. Several types of glucose sensing systems (including materials used for electrochemical, optical, and chemical sensing platforms) are discussed, in addition to various polymer-based release systems (including ethylene-vinyl acetate, polyanhydrides, and phenylboronic acid containing hydrogels).Juvenile Diabetes Research Foundation International (17-2007-1063)Leona M. and Harry B. Helmsley Charitable Trust (09PG-T1D027)United States. National Institutes of Health (F32 EB011580-01

Properties and customization of sensor materials for biomedical applications.

Low-power chemo- and biosensing devices capable of monitoring clinically important parameters in real time represent a great challenge in the analytical field as the issue of sensor calibration pertaining to keeping the response within an accurate calibration domain is particularly significant (1–4). Diagnostics, personal health, and related costs will also benefit from the introduction of sensors technology (5–7). In addition, with the introduction of Registration, Evaluation, Authorization, and Restriction of Chemical Substances (REACH) regulation, unraveling the cause–effect relationships in epidemiology studies will be of outmost importance to help establish reliable environmental policies aimed at protecting the health of individuals and communities (8–10). For instance, the effect of low concentration of toxic elements is seldom investigated as physicians do not have means to access the data (11)

Photobiocatalytic chemistry of oxidoreductases using water as the electron donor

[EN] To date, water has been poorly studied as the sacrificial electron donor for biocatalytic redox reactions using isolated enzymes. Here we demonstrate that water can also be turned into a sacrificial electron donor to promote biocatalytic redox reactions. The thermodynamic driving force required for water oxidation is obtained from UV and visible light by means of simple titanium dioxide-based photocatalysts. The electrons liberated in this process are delivered to an oxidoreductase by simple flavin redox mediators. Overall, the feasibility of photobiocatalytic, water-driven bioredox reactions is demonstrated.Financial support from the Spanish Science and Innovation Ministry (Consolider Ingenio 2010-MULTICAT CSD 2009-00050, Subprograma de apoyo a Centros y Universidades de Excelencia Severo Ochoa SEV 2012 0267). M. M. acknowledges the Spanish Science and Innovation Ministry for a 'Juan de la Cierva' postdoctoral contract. S. G. acknowledges the European Union Marie Curie Programme (ITN 'Biotrains', Grant Agreement No. 238531).Mifsud Grau, M.; Gargiulo, S.; Iborra Chornet, S.; Arends, IWCE.; Hollmann, F.; Corma Canós, A. (2014). Photobiocatalytic chemistry of oxidoreductases using water as the electron donor. Nature Communications. 5:1-6. https://doi.org/10.1038/ncomms4145S165Bornscheuer, U. T. et al. Engineering the third wave of biocatalysis. Nature 485, 185–194 (2012).Breuer, M. et al. Industrial methods for the production of optically active intermediates. Angew. Chem. Int. Ed. 43, 788–824 (2004).Pollard, D. J. & Woodley, J. M. Biocatalysis for pharmaceutical intermediates: the future is now. Trends Biotechnol. 25, 66–73 (2007).Ran, N., Zhao, L., Chen, Z. & Tao, J. Recent applications of biocatalysis in developing green chemistry for chemical synthesis at the industrial scale. Green. Chem. 10, 361–372 (2008).Schmid, A. et al. Industrial biocatalysis today and tomorrow. Nature 409, 258–268 (2001).Schmid, A., Hollmann, F., Park, J. B. & Bühler, B. The use of enzymes in the chemical industry in Europe. Curr. Opin. Biotechnol. 13, 359–366 (2002).Schoemaker, H. E., Mink, D. & Wubbolts, M. G. Dispelling the myths-biocatalysis in industrial synthesis. Science 299, 1694–1697 (2003).Turner, N. J. & O’Reilly, E. Biocatalytic retrosynthesis. Nat. Chem. Biol. 9, 285–288 (2013).Drauz K., Gröger H., May O. (eds)Enzyme Catalysis in Organic Synthesis Wiley-VCH: Weinheim, (2012).Weckbecker, A., Gröger, H. & Hummel, W. Regeneration of nicotinamide coenzymes: principles and applications for the synthesis of chiral compounds. inBiosystems Engineering I: Creating Superior Biocatalysts pp195–242Springer: Berlin, (2010).Van der Donk, W. A. & Zhao, H. Recent developments in pyridine nucleotide regeneration. Curr. Opin. Biotechnol. 14, 421–426 (2003).Wu, H. et al. Methods for the regeneration of nicotinamide coenzymes. Green. Chem. 15, 1773–1789 (2013).Rodriguez, C., Lavandera, I. & Gotor, V. Recent advances in cofactor regeneration systems applied to biocatalyzed oxidative processes. Curr. Org. Chem. 16, 2525–2541 (2012).Reipa, V., Mayhew, M. P. & Vilker, V. L. A direct electrode-driven P450 cycle for biocatalysis. Proc. Natl Acad. Sci. USA 94, 13554–13558 (1997).Bernard, J., van Heerden, E., Arends, I. W. C. E., Opperman, D. J. & Hollmann, F. Chemoenzymatic reduction of conjugated C=C double bonds. Chem. Cat. Chem. 4, 196–199 (2012).Hollmann, F., Arends, I. W. C. E. & Bühler, K. Biocatalytic redox reactions for organic synthesis: nonconventional regeneration methods. Chem. Cat. Chem. 2, 762–782 (2010).Hollmann, F., Hofstetter, K., Habicher, T., Hauer, B. & Schmid, A. Direct electrochemical regeneration of monooxygenase subunits for biocatalytic asymmetric epoxidation. J. Am. Chem. Soc. 127, 6540–6541 (2005).Hollmann, F., Lin, P.-C., Witholt, B. & Schmid, A. Stereospecific biocatalytic epoxidation: the first example of direct regeneration of a fad-dependent monooxygenase for catalysis. J. Am. Chem. Soc. 125, 8209–8217 (2003).Hollmann, F. & Schmid, A. Towards [Cp*Rh(bpy)(H2O)]2+-promoted P450 catalysis: direct regeneration of CytC. J. Inorg. Biochem. 103, 313–315 (2009).Hollmann, F., Taglieber, A., Schulz, F. & Reetz, M. T. A light-driven stereoselective biocatalytic oxidation. Angew. Chem. Int. Ed. 46, 2903–2906 (2007).Mifsud Grau, M. et al. Photoenzymatic reduction of C=C double bonds. Adv. Synth. Catal. 351, 3279–3286 (2009).Ruinatscha, R., Dusny, C., Buehler, K. & Schmid, A. Productive asymmetric styrene epoxidation based on a next generation electroenzymatic methodology. Adv. Synth. Catal. 351, 2505–2515 (2009).Schwaneberg, U., Appel, D., Schmitt, J. & Schmid, R. D. P450 in biotechnology: zinc driven ω-hydroxylation of p-nitrophenoxydodecanoic acid using P450 BM-3 F87A as a catalyst. J. Biotechnol. 84, 249–257 (2000).Taglieber, A., Schulz, F., Hollmann, F., Rusek, M. & Reetz, M. T. Light-Driven Biocatalytic Oxidation and Reduction Reactions: Scope and Limitations. Chem. Bio. Chem. 9, 565–572 (2008).Udit, A. K., Arnold, F. H. & Gray, H. B. Cobaltocene-mediated catalytic monooxygenation using holo and heme domain cytochrome P450 BM3. J. Inorg. Biochem. 98, 1547–1550 (2004).Udit, A. K., Hill, M. G., Bittner, V. G., Arnold, F. H. & Gray, H. B. Reduction of dioxygen catalyzed by pyrene-wired heme domain cytochrome p450 bm3 electrodes. J. Am. Chem. Soc. 126, 10218–10219 (2004).Unversucht, S., Hollmann, F., Schmid, A. & van Pée, K.-H. FADH2-Dependence of Tryptophan 7-Halogenase. Adv. Synth. Catal. 347, 1163–1167 (2005).Zilly, F. E., Taglieber, A., Schulz, F., Hollmann, F. & Reetz, M. T. Deazaflavins as mediators in light-driven cytochrome P450 catalyzed hydroxylations. Chem. Commun. 7152–7154 (2009).Yehezkeli, O. et al. Integrated photosystem II-based photo-bioelectrochemical cells. Nat. Commun. 3, 742 (2012).Duan, L. et al. A molecular ruthenium catalyst with water-oxidation activity comparable to that of photosystem II. Nat. Chem. 4, 418–423 (2012).Dau, H., Zaharieva, I. & Haumann, M. Recent developments in research on water oxidation by photosystem II. Curr. Opin. Chem. Biol. 16, 3–10 (2012).Qu, Y. & Duan, X. Progress, challenge and perspective of heterogeneous photocatalysts. Chem. Soc. Rev. 42, 2568–2580 (2013).Takanabe, K. & Domen, K. Preparation of inorganic photocatalytic materials for overall water splitting. Chem. Cat. Chem. 4, 1485–1497 (2012).Wee, T.-L. et al. Photochemical synthesis of a water oxidation catalyst based on cobalt nanostructures. J. Am. Chem. Soc. 133, 16742–16745 (2011).Cargnello, M. & Fornasiero, P. Photocatalysis by nanostructured TiO2 based semiconductors. inHandbook of Green Chemistry, Green Nanoscience (eds Selva M., Perosa A. Wiley-VCH: Weinheim, (2010).Liu, S. Q. & Chen, A. C. Coadsorption of horseradish peroxidase with thionine on TiO2: Nanotubes for biosensing. Langmuir 21, 8409–8413 (2005).Zhang, Y., He, P. L. & Hu, N. F. Horseradish peroxidase immobilized in TiO2 nanoparticle films on pyrolytic graphite electrodes: direct electrochemistry and bioelectrocatalysis. Electrochim. Acta 49, 1981–1988 (2004).Chen, D., Zhang, H., Li, X. & Li, J. H. Biofunctional titania nanotubes for visible-light-activated photoelectrochemical biosensing. Anal. Chem. 82, 2253–2261 (2010).Gomes Silva, C. U., Juárez, R., Marino, T., Molinari, R. & García, H. Influence of excitation wavelength (UV or visible light) on the photocatalytic activity of titania containing gold nanoparticles for the generation of hydrogen or oxygen from water. J. Am. Chem. Soc. 133, 595–602 (2010).Opperman, D. J., Piater, L. A. & van Heerden, E. A novel chromate reductase from Thermus scotoductus SA-01 related to old yellow enzyme. J. Bacteriol. 190, 3076–3082 (2008).Opperman, D. J. et al. Crystal structure of a thermostable old yellow enzyme from Thermus scotoductus SA-01. Biochem. Biophys. Res. Commun. 393, 426–431 (2010).Choi, S. H. et al. The influence of non-stoichiometric species of V/TiO2 catalysts on selective catalytic reduction at low temperature. J. Mol. Catal. A: Chem. 304, 166–173 (2009)