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1.
Adv Sci (Weinh) ; : e2401947, 2024 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-38868908

RESUMO

Perspiration plays a pivotal role not only in thermoregulation but also in reflecting the body's internal state and its response to external stimuli. The up-to-date skin-based wearable platforms have facilitated the monitoring and simultaneous analysis of sweat, offering valuable physiological insights. Unlike conventional passive sweating, dynamic normal perspiration, which occurs during various activities and rest periods, necessitates a more reliable method of collection to accurately capture its real-time fluctuations. An innovative microfluidic patch incorporating a hierarchical superhydrophilic biosponge, poise to significantly improve the efficiency capture of dynamic sweat is introduced. The seamlessly integrated biosponge microchannel showcases exceptional absorption capabilities, efficiently capturing non-sensitive sweat exuding from the skin surface, mitigating sample loss and minimizing sweat volatilization. Furthermore, the incorporation of sweat-rate sensors alongside a suite of functional electrochemical sensors endows the patch of uninterrupted monitoring and analysis of dynamic sweat during various activities, stress events, high-energy intake, and other scenarios.

2.
Biosensors (Basel) ; 13(12)2023 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-38131778

RESUMO

Nanomaterials, including carbon nanotubes, graphene oxide, metal-organic frameworks, metal nanoparticles, and porous carbon, play a crucial role as efficient carriers to enhance enzyme activity through substrate channeling while improving enzyme stability and reusability. However, there are significant debates surrounding aspects such as enzyme orientation, enzyme loading, retention of enzyme activity, and immobilization techniques. Consequently, these subjects have become the focus of intensive research in the realm of multi-enzyme cascade reactions. Researchers have undertaken the challenge of creating functional in vitro multi-enzyme systems, drawing inspiration from natural multi-enzyme processes within living organisms. Substantial progress has been achieved in designing multi-step reactions that harness the synthetic capabilities of various enzymes, particularly in applications such as biomarker detection (e.g., biosensors) and the development of biofuel cells. This review provides an overview of recent developments in concurrent and sequential approaches involving two or more enzymes in sequence. It delves into the intricacies of multi-enzyme cascade reactions conducted on nanostructured electrodes, addressing both the challenges encountered and the innovative solutions devised in this field.


Assuntos
Fontes de Energia Bioelétrica , Técnicas Biossensoriais , Nanoestruturas , Nanotubos de Carbono , Humanos , Enzimas Imobilizadas/química , Nanotubos de Carbono/química , Nanoestruturas/química , Técnicas Biossensoriais/métodos , Eletrodos
3.
Biosensors (Basel) ; 13(4)2023 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-37185557

RESUMO

Biofuel cells (BFCs) with enzymatic electrocatalysts have attracted significant attention, especially as power sources for wearable and implantable devices; however, the applications of BFCs are limited owing to the limited O2 supply. This can be addressed by using air-diffusion-type bilirubin oxidase (BOD) cathodes, and thus the further development of the hierarchical structure of porous electrodes with highly effective specific surface areas is critical. In this study, a porous layer of gold is deposited over magnesium-oxide-templated carbon (MgOC) to form BOD-based biocathodes for the oxygen reduction reaction (ORR). Porous gold structures are constructed via electrochemical deposition of gold via dynamic hydrogen bubble templating (DHBT). Hydrogen bubbles used as a template and controlled by the Coulomb number yield a porous gold structure during the electrochemical deposition process. The current density of the ORR catalyzed by BOD without a redox mediator on the gold-modified MgOC electrode was 1.3 times higher than that of the ORR on the MgOC electrode. Furthermore, the gold-deposited electrodes were modified with aromatic thiols containing negatively charged functional groups to improve the orientation of BOD on the electrode surface to facilitate efficient electron transfer at the heterogeneous surface, thereby achieving an ORR current of 12 mA cm-2 at pH 5 and 25 °C. These results suggest that DHBT is an efficient method for the fabrication of nanostructured electrodes that promote direct electron transfer with oxidoreductase enzymes.


Assuntos
Fontes de Energia Bioelétrica , Carbono , Carbono/química , Ouro/química , Oxigênio/química , Eletrodos , Hidrogênio , Enzimas Imobilizadas/química
4.
Mikrochim Acta ; 190(5): 177, 2023 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-37022500

RESUMO

According to the latest statistics, more than 537 million people around the world struggle with diabetes and its adverse consequences. As well as acute risks of hypo- or hyper- glycemia, long-term vascular complications may occur, including coronary heart disease or stroke, as well as diabetic nephropathy leading to end-stage disease, neuropathy or retinopathy. Therefore, there is an urgent need to improve diabetes management to reduce the risk of complications but also to improve patient's quality life. The impact of continuous glucose monitoring (CGM) is well recognized, in this regard. The current review aims at introducing the basic principles of glucose sensing, including electrochemical and optical detection, summarizing CGM technology, its requirements, advantages, and disadvantages. The role of CGM systems in the clinical diagnostics/personal testing, difficulties in their utilization, and recommendations are also discussed. In the end, challenges and prospects in future CGM systems are discussed and non-invasive, wearable glucose biosensors are introduced. Though the scope of this review is CGMs and provides information about medical issues and analytical principles, consideration of broader use will be critical in future if the right systems are to be selected for effective diabetes management.


Assuntos
Glicemia , Diabetes Mellitus , Humanos , Automonitorização da Glicemia , Diabetes Mellitus/diagnóstico , Glucose
5.
Biosens Bioelectron ; 230: 115272, 2023 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-37023550

RESUMO

It is essential to construct a biofuel cell-based sensor and develop an effective strategy to detect glucose without any potentiostat circuitry in order to create a simple and miniaturized device. In this report, an enzymatic biofuel cell (EBFC) is fabricated by the facile design of an anode and cathode on a screen-printed carbon electrode (SPCE). To construct the anode, thionine and flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) are covalently immobilized via a crosslinker to make a cross-linked redox network. As a cathode, the Pt-free oxygen reduction carbon catalyst is employed alternative to the commonly used bilirubin oxidase. We proposed the importance of EBFC-based sensors through the connection of anode and cathode; they can identify a short-circuit current by means of applied zero external voltage, thereby capable of glucose detection without under the operation of the potentiostat. The result shows that the EBFC-based sensor could be able to detect based on a short-circuit current with a wide range of glucose concentrations from 0.28 to 30 mM. Further, an EBFC is employed as a one-compartment model energy harvester with a maximum power density of (36 ± 3) µW cm- 2 in sample volume 5 µL. In addition, the constructed EBFC-based sensor demonstrates that the physiological range of ascorbic acid and uric acid shows no significant effect on the short-circuit current generation. Moreover, this EBFC can be used as a sensor in artificial plasma without losing its performance and thereby used as a disposable test strip in real blood sample analysis.


Assuntos
Fontes de Energia Bioelétrica , Técnicas Biossensoriais , Glucose/análise , Glucose 1-Desidrogenase , Eletrodos , Glucose Oxidase
6.
Sci Rep ; 12(1): 14649, 2022 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-36030337

RESUMO

In this study, the performance of a paper-based, screen-printed biofuel cell with mesoporous MgO-templated carbon (MgOC) electrodes was improved in two steps. First, a small amount of carboxymethyl cellulose (CMC) was added to the MgOC ink. Next, the cathode was modified with bilirubin prior to immobilizing the bilirubin oxidase (BOD). The CMC increased the accessibility of the mesopores of the MgOC, and subsequently, the performance of both the bioanode and biocathode. CMC also likely increased the stability of the electrodes. The pre-modification with bilirubin improved the orientation of the BOD, which facilitated direct electron transfer. With these two steps, an open circuit potential of 0.65 V, a maximal current density of 1.94 mA cm-2, and a maximal power density of 465 µW cm-2 was achieved with lactate oxidase as bioanode enzyme and lactate as fuel. This is one of the highest reported performances for a biofuel cell.


Assuntos
Fontes de Energia Bioelétrica , Carbono , Bilirrubina , Eletrodos , Enzimas Imobilizadas , Glucose , Tinta , Oxirredutases atuantes sobre Doadores de Grupo CH-CH
7.
ACS Sens ; 6(9): 3409-3415, 2021 09 24.
Artigo em Inglês | MEDLINE | ID: mdl-34264071

RESUMO

A self-driven sensor that can detect urine and urine sugar and can be mounted on diapers is desirable to reduce the burden of long-term care. In this study, we created a paper-based glucose biofuel cell that can be mounted on diapers to detect urine sugar. Electrodes for biofuel cells were produced by printing MgO-templated porous carbon on which poly(glycidyl methacrylate) was modified using graft polymerization. A new bioanode was prepared through covalently modifying flavin-adenine-dinucleotide-dependent glucose dehydrogenase and azure A with pendant glycidyl groups of poly(glycidyl methacrylate). We prepared a cathode with covalently bonded bilirubin oxidase. Covalent bonding of enzymes and mediators to both the bioanode and biocathode suppressed elution and improved stability. The biofuel cell could achieve a maximum output density of 0.12 mW cm-2, and by combining it with a wireless transmission device, the concentration of glucose sensed from the transmission frequency was in the range of 0-10 mM. The sensitivity of the sensor was estimated at 0.0030 ± 0.0002 Hz mmol-1 dm3. This device is expected to be a new urine-sugar detection device, composed only of organic materials with a low environmental load and it can be useful for detecting postprandial hyperglycemia.


Assuntos
Fontes de Energia Bioelétrica , Glucose
8.
Chem Commun (Camb) ; 57(57): 6999-7002, 2021 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-34159977

RESUMO

A bio-conjugated redox network matrix based on glucose dehydrogenase, thionine (diamine-containing mediator), and poly(ethylene glycol) diglycidyl ether (crosslinker) is developed on a glassy carbon electrode through covalent bonding with one-pot crosslinking. Electrons from the enzyme diffuse through the network producing 400 µA cm-2 of glucose oxidation current at 25 °C.


Assuntos
Técnicas Biossensoriais/métodos , Glucose 1-Desidrogenase/metabolismo , Biocatálise , Carbono/química , Técnicas Eletroquímicas , Eletrodos , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Glucose/química , Glucose 1-Desidrogenase/química , Oxirredução
9.
Biosens Bioelectron ; 189: 113357, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34051384

RESUMO

Glucose level measurement is essential for the point-of-care diagnosis, primarily for persons with diabetes. A disposable electrochemical glucose sensor is constructed using flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) and redox mediator for electron transfer from the enzyme to the electrode surface. Ideally, a suitable mediator should have high water solubility, high kinetic constant, high stability, and redox potential between -0.2 and 0.1 V vs. Ag|AgCl|sat. KCl. We designed and synthesized two new quinone-based water-soluble mediators: quinoline-5,8-dione (QD) and isoquinoline-5,8-dione (IQD). The formal potentials for both QD and IQD at pH 7.0 were -0.07 V vs. Ag|AgCl|sat. KCl. The logarithms of the electron exchange rate constants (k2/(M-1 s-1)) between QD/IQD and FAD-GDH were 7.7 ± 0.1 and 7.4 ± 0.1 for QD and IQD, respectively, which are the highest value among the water-soluble mediators for FAD-GDH reported to date. Disposable amperometric glucose sensors were fabricated by dropping FAD-GDH and QD or IQD onto a test strip. The sensor achieved a linear response up to glucose concentrations of 55.5 mM. The linear response was obtained even when the mediator loading was low (0.5 nmol/strip); loading was only 0.2 mol% of glucose. The results proved that the response current was primarily controlled by glucose diffusion. In addition, the sensor using QD exhibited high stability over 3 months at room temperature.


Assuntos
Técnicas Biossensoriais , Glucose 1-Desidrogenase , Flavina-Adenina Dinucleotídeo , Glucose , Água
10.
Bioelectrochemistry ; 137: 107637, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32898791

RESUMO

Extracellular electron transfer (EET) by the cyanobacterium Microcystis aeruginosa was investigated. Observations indicate that EET onto an electrode poised at + 0.6 vs. standard hydrogen electrode (SHE) is triggered by high pH, more evidently at pH levels above 9. Light intensity does not appear to affect electricity generation, indicating that this may not be a "biophotovoltaic" process. The generated current density was amplified with stepwise pH increases from approximately 5 mA m-2 at pH 7.8 to 30 mA m-2 at pH 10.5, for dense (0.4 mg mL-1 dry weight) Microcystis aeruginosa suspensions with dissolved CO2 and O2 approaching equilibrium with atmospheric concentrations. The upsurge in current density was more pronounced (from 5 mA m-2 at pH 7.8 to 40 mA m-2 at pH 10.2) in the absence of the cells' natural electron acceptors, dissolved CO2 and O2. However, the latter effect is more likely due to competition for electrons by oxygen than to reductive stress. EET in this species is therefore a light-independent process that is enhanced by increasing pH, with reasons that are still unknown, but either related to the involvement of protons in the last step of electron transfer, or to intracellular pH control.


Assuntos
Concentração de Íons de Hidrogênio , Microcystis/metabolismo , Transporte de Elétrons , Luz
11.
RSC Adv ; 11(33): 20550-20556, 2021 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-35479878

RESUMO

In this study, magnesium oxide (MgO)-templated mesoporous carbon (MgOC) and chitosan cross-linked with genipin (chitosan-genipin) were considered bio-composite inks for screen-printed bioanodes. The fabrication processes were optimized using rheological and structural data, and a bioanode ink containing glucose oxidase (GOx) and 1,2-naphthoquinone (1,2-NQ) was successfully developed. The optimal bioanode-ink contained MgOC pre-treated by washing to achieve a hydrophilic and neutral surface, which helped maintain enzyme activity and resulted in a highly porous electrode structure, which is essential for the accessibility of glucose to GOx. A bioanode fabricated using this ink showed a linear response current dependency up to 8 mM glucose with a sensitivity of 25.83 µA cm-2 mM-1. Combined with a conventional biocathode, an electromotive force of 0.54 V and a maximal power density of 96 µW cm-2 were achieved. These results show that this bio-composite ink can be used to replace the multi-step process of printing with conventional ink followed by drop-casting enzyme and mediator with a one-step printing process.

12.
Colloids Surf B Biointerfaces ; 192: 111065, 2020 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-32361503

RESUMO

Electrochemically polymerized phenothiazines (thionine, methylene green, methylene blue, and toluidine blue) on carbon electrodes were investigated as electron transfer mediators of glucose oxidation by flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) for biosensor and biofuel cell applications. Among the tested polyphenothiazines grafted on a glassy carbon electrode, clear redox-mediating activity was observed for poly(methylene green), and the catalytic oxidation current depended on the concentrations of glucose and enzymes and the amount of polymer deposited on the electrode surface. The poly(methylene green)-grafted porous carbon electrodes showed 3 mA cm-2 of glucose oxidation current catalyzed by FAD-GDH.

13.
Biosci Biotechnol Biochem ; 83(1): 39-48, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30274547

RESUMO

In this review, I present the main highlights of my works in the development of bioelectrocatalysis, which can be used in widespread applications, particularly for the design of biosensor and biofuel cells. In particular, I focus on research progress made in two key bioelectrocatalytic reactions: glucose oxidation by flavin adenine dinucleotide-dependent glucose dehydrogenase and oxygen reduction by bilirubin oxidase. I demonstrate the fundamental principles of bioelectrocatalysis and the requirements for enhancing the catalytic performance, including the choice of a mediator of redox reactions, immobilization, and electrode materials. These methods can allow for achieving control of the bioelectrocatalytic reaction, thereby overcoming obstacles toward their industrial applications.


Assuntos
Biocatálise , Fontes de Energia Bioelétrica , Técnicas Eletroquímicas/métodos , Enzimas Imobilizadas/metabolismo , Flavina-Adenina Dinucleotídeo/metabolismo , Glucose 1-Desidrogenase/metabolismo , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Aspergillus/enzimologia , Análise da Demanda Biológica de Oxigênio , Técnicas Biossensoriais , Carbono/química , Técnicas Eletroquímicas/instrumentação , Eletrodos , Hidrogéis , Oxirredução
14.
ChemElectroChem ; 4(10): 2460-2463, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-29214125

RESUMO

A novel paper-based biofuel cell with a series/parallel array structure has been fabricated, in which the cell voltage and output power can easily be adjusted as required by printing. The output of the fabricated 4-series/4-parallel biofuel cell reached 0.97±0.02 mW at 1.4 V, which is the highest output power reported to date for a paper-based biofuel cell. This work contributes to the development of flexible, wearable energy storage device.

15.
PLoS One ; 12(5): e0178974, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28558054

RESUMO

[This corrects the article DOI: 10.1371/journal.pone.0175846.].

16.
PLoS One ; 12(4): e0175846, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28410434

RESUMO

In general, hemoproteins are capable of catalyzing redox reactions. Aldoxime dehydratase (OxdA), which is a unique heme-containing enzyme, catalyzes the dehydration of aldoximes to the corresponding nitriles. Its reaction is a rare example of heme directly activating an organic substrate, unlike the utilization of H2O2 or O2 as a mediator of catalysis by other heme-containing enzymes. While it is unknown whether OxdA catalyzes redox reactions or not, we here for the first time detected catalase activity (which is one of the redox activities) of wild-type OxdA, OxdA(WT). Furthermore, we constructed a His320 → Asp mutant of OxdA [OxdA(H320D)], and found it exhibits catalase activity. Determination of the kinetic parameters of OxdA(WT) and OxdA(H320D) revealed that their Km values for H2O2 were similar to each other, but the kcat value of OxdA(H320D) was 30 times higher than that of OxdA(WT). Next, we examined another redox activity and found it was the peroxidase activity of OxdAs. While both OxdA(WT) and OxdA(H320D) showed the activity, the activity of OxdA(H320D) was dozens of times higher than that of OxdA(WT). These findings demonstrated that the H320D mutation enhances the peroxidase activity of OxdA. OxdAs (WT and H320D) were found to catalyze another redox reaction, a peroxygenase reaction. During this reaction of OxdA(H320D) with 1-methoxynaphthalene as a substrate, surprisingly, the reaction mixture changed to a color different from that with OxdA(WT), which was due to the known product, Russig's blue. We purified and identified the new product as 1-methoxy-2-naphthalenol, which has never been reported as a product of the peroxygenase reaction, to the best of our knowledge. These findings indicated that the H320D mutation not only enhanced redox activities, but also significantly altered the hydroxylation site of the substrate.


Assuntos
Proteínas de Bactérias/metabolismo , Hidroliases/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Biocatálise , Cromatografia Líquida de Alta Pressão , Guaiacol/química , Hidroliases/química , Hidroliases/genética , Peróxido de Hidrogênio/química , Peróxido de Hidrogênio/metabolismo , Cinética , Espectrometria de Massas , Mutagênese Sítio-Dirigida , Naftalenos/análise , Naftalenos/química , Naftalenos/metabolismo , Oxirredução , Pseudomonas chlororaphis/enzimologia , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/genética , Especificidade por Substrato
17.
Sci Rep ; 7: 45147, 2017 03 23.
Artigo em Inglês | MEDLINE | ID: mdl-28332583

RESUMO

We designed a three-dimensional (3D) hierarchical pore structure to improve the current production efficiency and stability of direct electron transfer-type biocathodes. The 3D hierarchical electrode structure was fabricated using a MgO-templated porous carbon framework produced from two MgO templates with sizes of 40 and 150 nm. The results revealed that the optimal pore composition for a bilirubin oxidase-catalysed oxygen reduction cathode was a mixture of 33% macropores and 67% mesopores (MgOC33). The macropores improve mass transfer inside the carbon material, and the mesopores improve the electron transfer efficiency of the enzyme by surrounding the enzyme with carbon.

18.
Int J Mol Sci ; 18(3)2017 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-28287419

RESUMO

The flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) from Aspergillus species require suitable redox mediators to transfer electrons from the enzyme to the electrode surface for the application of bioelectrical devices. Although several mediators for FAD-GDH are already in use, they are still far from optimum in view of potential, kinetics, sustainability, and cost-effectiveness. Herein, we investigated the efficiency of various phenothiazines and quinones in the electrochemical oxidation of FAD-GDH from Aspergillus terreus. At pH 7.0, the logarithm of the bimolecular oxidation rate constants appeared to depend on the redox potentials of all the mediators tested. Notably, the rate constant of each molecule for FAD-GDH was approximately 2.5 orders of magnitude higher than that for glucose oxidase from Aspergillus sp. The results suggest that the electron transfer kinetics is mainly determined by the formal potential of the mediator, the driving force of electron transfer, and the electron transfer distance between the redox active site of the mediator and the FAD, affected by the steric or chemical interactions. Higher k2 values were found for ortho-quinones than for para-quinones in the reactions with FAD-GDH and glucose oxidase, which was likely due to less steric hindrance in the active site in the case of the ortho-quinones.


Assuntos
Aspergillus/enzimologia , Flavina-Adenina Dinucleotídeo/metabolismo , Proteínas Fúngicas/metabolismo , Glucose Desidrogenase/metabolismo , Benzoquinonas/metabolismo , Cinética , Oxirredução , Fenotiazinas/metabolismo
19.
Biosens Bioelectron ; 63: 138-144, 2015 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-25078712

RESUMO

Effects of the electrode poential on the activity of an adsorbed enzyme has been examined by using copper efflux oxidase (CueO) as a model enzyme and by monitoring direct electron transfer (DET)-type bioelectrocatalysis of oxygen reduction. CueO adsorbed on bare Au electrodes at around the point of zero charge (E(pzc)) shows the highest DET activity, and the activity decreases as the adsorption potential (E(ad); at which the enzyme adsorbs) is far from E(pzc). We propose a model to explain the phenomena in which the electrostatic interaction between the enzyme and electrodes in the electric double layer affects the orientation and the stability of the adsorbed enzyme. The self-assembled monolayer of butanethiol on Au electrodes decreases the electric field in the outside of the inner Helmholtz plane and drastically diminishes the E(ad) dependence of the DET activity of CueO. When CueO is adsorbed on bare Au electrodes under open circuit potential and then is held at hold potentials (E(ho)) more positive than E(pzc), the DET activity of the CueO rapidly decreases with the hold time. The strong electric field with positive surface charge density on the metallic electrode (σ(M)) leads to fatal denaturation of the adsorbed CueO. Such denaturation effect is not so serious at E(ho)<

Assuntos
Técnicas Biossensoriais , Catálise , Oxirredutases/isolamento & purificação , Adsorção , Eletricidade , Transporte de Elétrons , Ouro/química , Oxirredutases/química , Desnaturação Proteica , Compostos de Sulfidrila/química , Propriedades de Superfície
20.
J Am Chem Soc ; 136(41): 14432-7, 2014 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-25244161

RESUMO

This article introduces a carbon electrode designed to achieve efficient enzymatic electrolysis by exploiting a hierarchical pore structure based on macropores for efficient mass transfer and mesopores for high enzyme loading. Magnesium oxide-templated mesoporous carbon (MgOC, mean pore diameter 38 nm) was used to increase the effective specific surface area for enzyme immobilization. MgOC particles were deposited on a current collector by an electrophoretic deposition method to generate micrometer-scale macropores to improve the mass transfer of glucose and electrolyte (buffer) ions. To create a glucose bioanode, the porous-carbon-modified electrode was further coated with a biocatalytic hydrogel composed of a conductive redox polymer, deglycosylated flavin adenine dinucleotide-dependent glucose dehydrogenase (d-FAD-GDH), and a cross-linker. Carbohydrate chains on the peripheral surfaces of the FAD-GDH molecules were removed by periodate oxidation before cross-linking. The current density for the oxidation of glucose was 100 mA cm(-2) at 25 °C and pH 7, with a hydrogel loading of 1.0 mg cm(-2). For the same hydrogel composition and loading, the current density on the MgOC-modified electrode was more than 30 times higher than that on a flat carbon electrode. On increasing the solution temperature to 45 °C, the catalytic current increased to 300 mA cm(-2), with a hydrogel loading of 1.6 mg cm(-2). Furthermore, the stability of the hydrogel electrode was improved by using the mesoporous carbon materials; more than 95% of the initial catalytic current remained after a 220-day storage test in 4 °C phosphate buffer, and 80% was observed after 7 days of continuous operation at 25 °C.


Assuntos
Carbono/química , Flavina-Adenina Dinucleotídeo/química , Glucose 1-Desidrogenase/química , Glucose/química , Carbono/metabolismo , Eletrodos , Flavina-Adenina Dinucleotídeo/metabolismo , Glucose/metabolismo , Glucose 1-Desidrogenase/metabolismo , Estrutura Molecular , Porosidade , Propriedades de Superfície
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