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Kabir MH, Marquez E, Djokoto G, Parker M, Weinstein T, Ghann W, Uddin J, Ali MM, Alam MM, Thompson M, Poyraz AS, Msimanga HZ, Rahman MM, Rulison M, Cramer J. Energy Harvesting by Mesoporous Reduced Graphene Oxide Enhanced the Mediator-Free Glucose-Powered Enzymatic Biofuel Cell for Biomedical Applications. ACS APPLIED MATERIALS & INTERFACES 2022; 14:24229-24244. [PMID: 35594363 DOI: 10.1021/acsami.1c25211] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Harnessing electrochemical energy in an engineered electrical circuit from biochemical substrates in the human body using biofuel cells is gaining increasing research attention in the current decade due to the wide range of biomedical possibilities it creates for electronic devices. In this report, we describe and characterize the construction of just such an enzymatic biofuel cell (EBFC). It is simple, mediator-free, and glucose-powered, employing only biocompatible materials. A novel feature is the two-dimensional mesoporous thermally reduced graphene oxide (rGO) host electrode. An additionally novelty is that we explored the potential of using biocompatible, low-cost filter paper (FP) instead of carbon paper, a conductive polymer, or gold as support for the host electrode. Using glucose (C6H12O6) and molecular oxygen (O2) as the power-generating fuel, the cell consists of a pair of bioelectrodes incorporating immobilized enzymes, the bioanode modified by rGO-glucose oxidase (GOx/rGO), and the biocathode modified by rGO-laccase (Lac/rGO). Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), transmission electron microscopy, and Raman spectroscopy techniques have been employed to investigate the surface morphology, defects, and chemical structure of rGO, GOx/rGO, and Lac/rGO. N2 sorption, SEM/EDX, and powder X-ray diffraction revealed a high Brunauer-Emmett-Teller surface area (179 m2 g-1) mesoporous rGO structure with the high C/O ratio of 80:1 as well. Results from the Fourier transform infrared spectroscopy, UV-visible spectroscopy, and electrochemical impedance spectroscopy studies indicated that GOx remained in its native biochemical functional form upon being embedded onto the rGO matrix. Cyclic voltammetry studies showed that the presence of mesoporous rGO greatly enhanced the direct electrochemistry and electrocatalytic properties of the GOx/rGO and Lac/rGO nanocomposites. The electron transfer rate constant between GOx and rGO was estimated to be 2.14 s-1. The fabricated EBFC (GOx/rGO/FP-Lac/rGO/FP) using a single GOx/rGO/FP bioanode and a single Lac/rGO/FP biocathode provides a maximum power density (Pmax) of 4.0 nW cm-2 with an open-circuit voltage (VOC) of 0.04 V and remains stable for more than 15 days with a power output of ∼9.0 nW cm-2 at a pH of 7.4 under ambient conditions.
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Affiliation(s)
- Md Humayun Kabir
- Department of Chemistry and Occupational Health Science, University of North Alabama, Florence, Alabama 35632, United States
- Department of Chemistry and Biochemistry, Kennesaw State University, Kennesaw, Georgia 30144, United States
- Department of Chemistry, Oglethorpe University, Atlanta, Georgia 30319, United States
| | - Erik Marquez
- Department of Chemistry, Oglethorpe University, Atlanta, Georgia 30319, United States
| | - Grace Djokoto
- Department of Chemistry, Oglethorpe University, Atlanta, Georgia 30319, United States
| | - Maurice Parker
- Department of Chemistry, Oglethorpe University, Atlanta, Georgia 30319, United States
| | - Talia Weinstein
- Department of Chemistry, Oglethorpe University, Atlanta, Georgia 30319, United States
| | - William Ghann
- Center for Nanotechnology, Department of Natural Sciences, Coppin State University, Baltimore, Maryland 21216, United States
| | - Jamal Uddin
- Center for Nanotechnology, Department of Natural Sciences, Coppin State University, Baltimore, Maryland 21216, United States
| | - Meser M Ali
- Department of Neurosurgery, Cellular and Molecular Imaging Laboratory, Henry Ford Hospital, Detroit, Michigan 48202, United States
| | | | - Max Thompson
- Department of Chemistry and Biochemistry, Kennesaw State University, Kennesaw, Georgia 30144, United States
| | - Altug S Poyraz
- Department of Chemistry and Biochemistry, Kennesaw State University, Kennesaw, Georgia 30144, United States
| | - Huggins Z Msimanga
- Department of Chemistry and Biochemistry, Kennesaw State University, Kennesaw, Georgia 30144, United States
| | - Mohammed M Rahman
- Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Michael Rulison
- Department of Physics, Oglethorpe University, Atlanta, Georgia 30319, United States
| | - John Cramer
- Department of Physics, Oglethorpe University, Atlanta, Georgia 30319, United States
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Flexible and Conductive Bioelectrodes Based on Chitosan-Carbon Black Membranes: Towards the Development of Wearable Bioelectrodes. NANOMATERIALS 2021; 11:nano11082052. [PMID: 34443882 PMCID: PMC8398670 DOI: 10.3390/nano11082052] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 07/23/2021] [Accepted: 08/10/2021] [Indexed: 11/17/2022]
Abstract
Wearable sensors for non-invasive monitoring constitute a growing technology in many industrial fields, such as clinical or sport monitoring. However, one of the main challenges in wearable sensing is the development of bioelectrodes via the use of flexible and stretchable materials capable of maintaining conductive and biocompatible properties simultaneously. In this study, chitosan-carbon black (CH-CB) membranes have been synthesized using a straightforward and versatile strategy and characterized in terms of their composition and their electrical and mechanical properties. In this sense, CH-CB membranes showed good conductivity and mechanical resistance thanks to the presence of carbon black, which decreases the insulating behavior of chitosan, while flexibility and biocompatibility are maintained due to the dual composition of the membrane. Thus, flexible and biocompatible conductive bioelectrodes have been developed by the combined use of CH and CB without the use of toxic reagents, extra energy input, or long reaction times. The membranes were modified using the enzymes Glucose Oxidase and Laccase in order to develop flexible and biocompatible bioelectrodes for enzymatic glucose biofuel cells (BFCs) and glucose detection. A BFC assembled using the flexible bioelectrodes developed was able to deliver 15 µW cm-2, using just 1 mM glucose as biofuel, and up to 21.3 µW·cm-2 with higher glucose concentration. Additionally, the suitability of the CH-CB membranes to be used as a glucose sensor in a linear range from 100 to 600 µM with a limit of detection (LOD) of 76 µM has been proven. Such demonstrations for energy harvesting and sensing capabilities of the developed membrane pave the way for their use in wearable sensing and energy harvesting technologies in the clinical field due to their good mechanical, electrical, and biocompatible properties.
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NiO micro/nanoparticles decorated carbon-based anode for the fuel cell applications in alkaline medium. MONATSHEFTE FUR CHEMIE 2021. [DOI: 10.1007/s00706-021-02797-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Liu Q, Bai X, Pham H, Hu J, Dinu CZ. Active Nanointerfaces Based on Enzyme Carbonic Anhydrase and Metal-Organic Framework for Carbon Dioxide Reduction. NANOMATERIALS 2021; 11:nano11041008. [PMID: 33920833 PMCID: PMC8071118 DOI: 10.3390/nano11041008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 04/01/2021] [Accepted: 04/06/2021] [Indexed: 01/19/2023]
Abstract
Carbonic anhydrases are enzymes capable of transforming carbon dioxide into bicarbonate to maintain functionality of biological systems. Synthetic isolation and implementation of carbonic anhydrases into membrane have recently raised hopes for emerging and efficient strategies that could reduce greenhouse emission and the footprint of anthropogenic activities. However, implementation of such enzymes is currently challenged by the resulting membrane’s wetting capability, overall membrane performance for gas sensing, adsorption and transformation, and by the low solubility of carbon dioxide in water, the required medium for enzyme functionality. We developed the next generation of enzyme-based interfaces capable to efficiently adsorb and reduce carbon dioxide at room temperature. For this, we integrated carbonic anhydrase with a hydrophilic, user-synthesized metal–organic framework; we showed how the framework’s porosity and controlled morphology contribute to viable enzyme binding to create functional surfaces for the adsorption and reduction of carbon dioxide. Our analysis based on electron and atomic microscopy, infrared spectroscopy, and colorimetric assays demonstrated the functionality of such interfaces, while Brunauer–Emmett–Teller analysis and gas chromatography analysis allowed additional evaluation of the efficiency of carbon dioxide adsorption and reduction. Our study is expected to impact the design and development of active interfaces based on enzymes to be used as green approaches for carbon dioxide transformation and mitigation of global anthropogenic activities.
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Almunla M, Tepeli Büyüksünetçi Y, Akpolat O, Anık Ü. Development of Apple Tissue Based Biocathode and MWCNT−Pt−Au Nanomaterial Based Bioanode Biofuel Cell. ELECTROANAL 2020. [DOI: 10.1002/elan.202060425] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Moustafa Almunla
- Department of Bioinformatics Graduate School of Natural and Applied Sciences Muğla Sıtkı Kocman University Turkey
| | | | - Oğuz Akpolat
- Muğla Sıtkı Kocman University Faculty of Science Chemistry Department 48000- Kotekli Muğla Turkey
| | - Ülkü Anık
- Department of Bioinformatics Graduate School of Natural and Applied Sciences Muğla Sıtkı Kocman University Turkey
- Muğla Sıtkı Kocman University Faculty of Science Chemistry Department 48000- Kotekli Muğla Turkey
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Xiao X, Xia HQ, Wu R, Bai L, Yan L, Magner E, Cosnier S, Lojou E, Zhu Z, Liu A. Tackling the Challenges of Enzymatic (Bio)Fuel Cells. Chem Rev 2019; 119:9509-9558. [PMID: 31243999 DOI: 10.1021/acs.chemrev.9b00115] [Citation(s) in RCA: 177] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The ever-increasing demands for clean and sustainable energy sources combined with rapid advances in biointegrated portable or implantable electronic devices have stimulated intensive research activities in enzymatic (bio)fuel cells (EFCs). The use of renewable biocatalysts, the utilization of abundant green, safe, and high energy density fuels, together with the capability of working at modest and biocompatible conditions make EFCs promising as next generation alternative power sources. However, the main challenges (low energy density, relatively low power density, poor operational stability, and limited voltage output) hinder future applications of EFCs. This review aims at exploring the underlying mechanism of EFCs and providing possible practical strategies, methodologies and insights to tackle these issues. First, this review summarizes approaches in achieving high energy densities in EFCs, particularly, employing enzyme cascades for the deep/complete oxidation of fuels. Second, strategies for increasing power densities in EFCs, including increasing enzyme activities, facilitating electron transfers, employing nanomaterials, and designing more efficient enzyme-electrode interfaces, are described. The potential of EFCs/(super)capacitor combination is discussed. Third, the review evaluates a range of strategies for improving the stability of EFCs, including the use of different enzyme immobilization approaches, tuning enzyme properties, designing protective matrixes, and using microbial surface displaying enzymes. Fourth, approaches for the improvement of the cell voltage of EFCs are highlighted. Finally, future developments and a prospective on EFCs are envisioned.
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Affiliation(s)
- Xinxin Xiao
- Institute for Biosensing, and College of Life Sciences , Qingdao University , 308 Ningxia Road , Qingdao 266071 , China.,Department of Chemical Sciences and Bernal Institute , University of Limerick , Limerick V94 T9PX , Ireland
| | - Hong-Qi Xia
- Institute for Biosensing, and College of Life Sciences , Qingdao University , 308 Ningxia Road , Qingdao 266071 , China
| | - Ranran Wu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , 32 West seventh Road, Tianjin Airport Economic Area , Tianjin 300308 , China
| | - Lu Bai
- Institute for Biosensing, and College of Life Sciences , Qingdao University , 308 Ningxia Road , Qingdao 266071 , China
| | - Lu Yan
- Institute for Biosensing, and College of Life Sciences , Qingdao University , 308 Ningxia Road , Qingdao 266071 , China
| | - Edmond Magner
- Department of Chemical Sciences and Bernal Institute , University of Limerick , Limerick V94 T9PX , Ireland
| | - Serge Cosnier
- Université Grenoble-Alpes , DCM UMR 5250, F-38000 Grenoble , France.,Département de Chimie Moléculaire , UMR CNRS, DCM UMR 5250, F-38000 Grenoble , France
| | - Elisabeth Lojou
- Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines UMR7281 , Institut de Microbiologie de la Méditerranée, IMM , FR 3479, 31, chemin Joseph Aiguier 13402 Marseille , Cedex 20 , France
| | - Zhiguang Zhu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , 32 West seventh Road, Tianjin Airport Economic Area , Tianjin 300308 , China
| | - Aihua Liu
- Institute for Biosensing, and College of Life Sciences , Qingdao University , 308 Ningxia Road , Qingdao 266071 , China.,College of Chemistry & Chemical Engineering , Qingdao University , 308 Ningxia Road , Qingdao 266071 , China.,School of Pharmacy, Medical College , Qingdao University , Qingdao 266021 , China
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Tsui MN, Kim KH, Islam MF. Drastically Enhancing Moduli of Graphene-Coated Carbon Nanotube Aerogels via Densification while Retaining Temperature-Invariant Superelasticity and Ultrahigh Efficiency. ACS APPLIED MATERIALS & INTERFACES 2017; 9:37954-37961. [PMID: 28991429 DOI: 10.1021/acsami.7b12243] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Lightweight open-cell foams that are simultaneously superelastic, possess exceptionally high Young's moduli (Y), exhibit ultrahigh efficiency, and resist fatigue as well as creep are particularly desirable as structural frameworks. Unfortunately, many of these features are orthogonal in foams of metals, ceramics, and polymers, particularly under large temperature variations. In contrast, foams of carbon allotropes including carbon nanotubes and graphene developed over the past few years exhibit these desired properties but have low Y due to low density, ρ = 0.5-10 mg/mL. Densification of these foams enhances Y although below expectation and also dramatically degrades other properties because of drastic changes in microstructure. We have recently developed size- and shape-tunable graphene-coated single-walled carbon nanotube (SWCNT) aerogels that display superelasticity at least up to a compressive strain (ε) = 80%, fatigue and creep resistance, and ultrahigh efficiency over -100-500 °C. Unfortunately, Y of these aerogels is only ∼0.75 MPa due to low ρ ≈ 14 mg/mL, limiting their competitiveness as structural foams. We report fabrication of similar aerogels but with ρ spanning more than an order of magnitude from 16-400 mg/mL through controlled isostatic compression in the presence of a polymer coating circumventing any microstructural changes in stark contrast to other foams of carbon allotropes. The compressive stress (σ) versus ε measurements show that the densification of aerogels from ρ ≈ 16 to 400 mg/mL dramatically enhances Y from 0.9 to 400 MPa while maintaining superelasticity at least up to ε = 10% even at the highest ρ. The storage (E') and loss (E″) moduli measured in the linear regime show ultralow loss coefficient, tan δ = E″/E' ≈ 0.02, that remains constant over three decades of frequencies (0.628-628 rad/s), suggesting unusually high frequency-invariant efficiency. Furthermore, these aerogels retain exceptional fatigue resistance for 106 loading-unloading cycles to ε = 2% and creep resistance for at least 30 min under σ = 0.02 MPa with ρ = 16 mg/mL and σ = 2.5 MPa with higher ρ = 400 mg/mL. Lastly, these robust mechanical properties are stable over a broad temperature range of -100-500 °C, motivating their use as highly efficient structural components in environments with extreme temperature variations.
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Affiliation(s)
- Michelle N Tsui
- Department of Materials Science and Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213-3815, United States
| | - Kyu Hun Kim
- Department of Materials Science and Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213-3815, United States
| | - Mohammad F Islam
- Department of Materials Science and Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213-3815, United States
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Affiliation(s)
- Nicolas Mano
- CNRS, CRPP, UPR 8641, 33600 Pessac, France
- University of Bordeaux, CRPP, UPR 8641, 33600 Pessac, France
| | - Anne de Poulpiquet
- Aix Marseille Univ., CNRS, BIP, 31, chemin Aiguier, 13402 Marseille, France
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Campbell AS, Islam MF, Russell AJ. Intramolecular Electron Transfer through Poly-Ferrocenyl Glucose Oxidase Conjugates to Carbon Electrodes: 2. Mechanistic Understanding of Long-Term Stability. Electrochim Acta 2017. [DOI: 10.1016/j.electacta.2017.06.066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Garg R, Rastogi SK, Lamparski M, de la Barrera SC, Pace GT, Nuhfer NT, Hunt BM, Meunier V, Cohen-Karni T. Nanowire-Mesh-Templated Growth of Out-of-Plane Three-Dimensional Fuzzy Graphene. ACS NANO 2017; 11:6301-6311. [PMID: 28549215 DOI: 10.1021/acsnano.7b02612] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Graphene, a honeycomb sp2 hybridized carbon lattice, is a promising building block for hybrid-nanomaterials due to its electrical, mechanical, and optical properties. Graphene can be readily obtained through mechanical exfoliation, solution-based deposition of reduced graphene oxide (rGO), and chemical vapor deposition (CVD). The resulting graphene films' topology is two-dimensional (2D) surface. Recently, synthesis of three-dimensional (3D) graphitic networks supported or templated by nanoparticles, foams, and hydrogels was reported. However, the resulting graphene films lay flat on the surface, exposing 2D surface topology. Out-of-plane grown carbon nanostructures, such as vertically aligned graphene sheets (VAGS) and vertical carbon nanowalls (CNWs), are still tethered to 2D surface. 3D morphology of out-of-plane growth of graphene hybrid-nanomaterials which leverages graphene's outstanding surface-to-volume ratio has not been achieved to date. Here we demonstrate highly controlled synthesis of 3D out-of-plane single- to few-layer fuzzy graphene (3DFG) on a Si nanowire (SiNW) mesh template. By varying graphene growth conditions (CH4 partial pressure and process time), we control the size, density, and electrical properties of the NW templated 3DFG (NT-3DFG). 3DFG growth can be described by a diffusion-limited-aggregation (DLA) model. The porous NT-3DFG meshes exhibited high electrical conductivity of ca. 2350 S m-1. NT-3DFG demonstrated exceptional electrochemical functionality, with calculated specific electrochemical surface area as high as ca. 1017 m2 g-1 for a ca. 7 μm thick mesh. This flexible synthesis will inspire formation of complex hybrid-nanomaterials with tailored optical and electrical properties to be used in future applications such as sensing, and energy conversion and storage.
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Affiliation(s)
| | | | - Michael Lamparski
- Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States
| | | | | | | | | | - Vincent Meunier
- Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States
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Tsui MN, Islam MF. Creep- and fatigue-resistant, rapid piezoresistive responses of elastomeric graphene-coated carbon nanotube aerogels over a wide pressure range. NANOSCALE 2017; 9:1128-1135. [PMID: 28009903 DOI: 10.1039/c6nr07432d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Lightweight, flexible piezoresistive materials with wide operational pressure ranges are in demand for applications such as human physical activity and health monitoring, robotics, and for functional interfacing between living systems and wearable electronics. Piezoresistivity of many elastomeric foams of polymers and carbon allotropes satisfies much of the required characteristics for these applications except creep and fatigue resistance due to their viscoelasticity, critically limiting the reliability and lifetime of integrated devices. We report the piezoresistive responses from aerogels of graphene-coated single-walled carbon nanotubes (SWCNTs), made using a facile and versatile sol-gel method. Graphene crosslinks the junctions of the underlying random network of SWCNTs, generating lightweight elastomeric aerogels with a mass density of ≈11 mg mL-1 (volume fraction ≈7.7 × 10-3) and a Young's modulus of ≈0.4 MPa. The piezoresistivity of these aerogels spans wide compressive pressures up to at least 120 kPa with sensitivity that exhibit ultrafast temporal responses of <27 ms and <3% delay ratio over 104 compressive loading-unloading cycles at rates between 0.1-10 Hz. Most importantly, the piezoresistive responses do not show any creep at least for 1 hour and 80 kPa of compressive static loading. We suggest that the fatigue- and creep-resistant, ultrafast piezoresistive responses of these elastomeric aerogels are highly attractive for use in dynamic and static lightweight, pressure sensing applications such as human activity monitoring and soft robotics.
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Affiliation(s)
- Michelle N Tsui
- Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA.
| | - Mohammad F Islam
- Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA.
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Campbell AS, Murata H, Carmali S, Matyjaszewski K, Islam MF, Russell AJ. Polymer-based protein engineering grown ferrocene-containing redox polymers improve current generation in an enzymatic biofuel cell. Biosens Bioelectron 2016; 86:446-453. [DOI: 10.1016/j.bios.2016.06.078] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 06/22/2016] [Accepted: 06/26/2016] [Indexed: 12/22/2022]
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Immobilization of bilirubin oxidase on graphene oxide flakes with different negative charge density for oxygen reduction. The effect of GO charge density on enzyme coverage, electron transfer rate and current density. Biosens Bioelectron 2016; 89:384-389. [PMID: 27297188 DOI: 10.1016/j.bios.2016.06.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 06/03/2016] [Accepted: 06/04/2016] [Indexed: 01/16/2023]
Abstract
Previously we showed that an effective bilirubin oxidase (BOD)-based biocathode using graphene oxide (GO) could be prepared in 2 steps: 1. electrostatic adsorption of BOD on GO; 2. electrochemical reduction of the BOD-GO composite to form a BOD-ErGO (electrochemically reduced GO) film on the electrode. In order to identify an optimal charge density of GO for BOD-ErGO composite preparation, several GO fractions differing in an average flake size and ζ-potential were prepared using centrifugation and consequently employed for BOD-ErGO biocathode preparation. A simple way to express surface charge density of these particular GO nanosheets was developed. The values obtained were then correlated with biocatalytic and electrochemical parameters of the prepared biocathodes, i.e. electrocatalytically active BOD surface coverage (Γ), heterogeneous electron transfer rate (kS) and a maximum biocatalytic current density. The highest bioelectrocatalytic current density of (597±25)μAcm-2 and the highest Γ of (23.6±0.9)pmolcm-2 were obtained on BOD-GO composite having the same moderate negative charge density, but the highest kS of (79.4±4.6)s-1 was observed on BOD-GO composite having different negative charge density. This study is a solid foundation for others to consider the influence of a charge density of GO on direct bioelectrochemistry/bioelectrocatalysis of other redox enzymes applicable for construction of biosensors, bioanodes, biocathodes or biofuel cells.
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