A novel alcohol dehydrogenase biosensor based on solid-state electrogenerated chemiluminescence by assembling dehydrogenase to Ru(bpy)(3)(2+)-Au nanoparticles aggregates

Based on electrogenerated chemiluminescence (ECL), a novel method for fabrication of alcohol dehydrogenase (ADH) biosensor by self-assembling ADH to Ru(bpy)(3)(2+) -AuNPs aggregates (Ru-AuNPs) on indium tin oxide (ITO) electrode surface has been developed. Positively charged Ru(bpy)(3)(2+) could be immobilized stably on the electrode surface with negatively charged AuNPs in the form of aggregate via electrostatic interaction. On the other hand, AuNPs are favourable candidates for the immobilization of enzymes because amine groups and cysteine residues in the enzymes are known to bind strongly with AuNPs. Moreover, AuNPs can act as tiny conduction centers to facilitate the transfer of electrons. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate, and it displayed wide linear range, high sensitivity and good stability.

A biofuel cell harvesting energy from glucose-air and fruit juice-air

The membraneless biofuel cell (BFC) is facile prepared based on glucose oxidase and laccase as anodic and cathodic catalyst, respectively, by using 1,1'-dicarboxyferrocene as the mediators of both anode and cathode. The BFC can work by taking glucose as fuel in air-saturated solution, in which air serves as the oxidizer of the cathode. More interestingly, the fruit juice containing glucose, e.g. grape, banana or orange juice as the fuels substituting for glucose can make the BFC work. The BFC shows several advantages which have not been reported to our knowledge: (1) it is membraneless BFC which can work with same mediator on both anode and cathode; (2) fruit juice can act as fuels of BFCs substituting for usually used glucose; (3) especially, the orange juice can greatly enhance the power output rather than that of glucose, grape or banana juice. Besides, the facile and simple preparation procedure and easy accessibility of fruit juice as well as air being whenever and everywhere imply that our system has promising potential for the development and practical application of BFCs.

Molecular "Wiring" glucose oxidase in supramolecular architecture

Supramolecular organized multilayers were constructed by multiwalled carbon nanotubes modified with ferrocene-derivatized poly(allylamine) redox polymer and glucose oxidase by electrostatic self-assembly. From the analysis of voltammetric signals and fluorescence results, a linear increment of the coverage of enzyme per bilayer was estimated, which demonstrated that the multilayer is constructed in a spatially ordered manner. The cyclic voltammograms obtained from the indium tin oxide (ITO) electrodes coated by the (Fc-PAH@CNT/GOx)(n) multilayers revealed that bioelectrocatalytic response is directly correlated to the number of deposited bilayers; that is, the sensitivity is tunable by controlling the number of bilayers associated with ITO electrodes. The incorporation of redox-polymer-functionalized carbon nanotubes (CNT) into enzyme films resulted in a 6-10-fold increase in the glucose electrocatalytic current; the bimolecular rate constant of FADH(2) oxidation (wiring efficiency) was increased up to 12-fold. Impedance spectroscopy data have yielded the electron diffusion coefficient (D-e) of this nanostructure to be over 10(-8) cm(2) s(-1), which is typically higher than those systems without CNT by at least a factor of 10, indicating that electron transport in the new supramolecular architecture was enhanced by communication of the redox active site of enzyme, redox polymer, and CNT.

A biofuel cell with enhanced power output by grape juice

Glucose oxidase and laccase immobilized at multiwalled carbon nanotubes-ionic liquid gel modified electrodes are used as the catalysts of anode and cathode of biofuel cells (BFCs), respectively. The BFC based on glucose and air is proposed. When ferrocene monocarboxylic acid is adopted as the mediator of anode, the power output of the BFC is ca. 4.1 mu W (power density ca. 10.0 mu W cm(-2)), which is higher than the value of 2.7 mu W (power density ca. 6.6 mu W cm(-2)) by taking ferrocene dicarboxylic acid as the mediator. This implies that the mediator with formal potential closing to that of the enzyme does improve the power output. Furthermore, the power output of the BFC is greatly improved by taking grape juice as the fuel of anode rather than glucose. This system also indicates that grape juice as a fuel of the BFC not only is feasible and can also enhances the power output of the BFCs. Besides, it greatly lowers the cost and simplifies the preparation procedure of the BFCs, making the BFC towards "green" bioenergy.

Electrochemical characteristics of glucose oxidase adsorbed at carbon nanotubes modified electrode with ionic liquid as binder

Multiwall carbon nanotubes (CNTs)-modified electrode has been prepared by using ionic liquid (IL) as the binder. The as-prepared CNTs-IL composite modified electrode has good biocompatibility and is a suitable matrix to immobilize biomolecules. Glucose oxidase (GOx), containing flavin adenine dinucleotide as active site, stably adsorbed on modified electrode surface has resulted in the direct electron transfer. The electron transfer rate of 9.08 s(-1) obtained is much higher than that of GOx adsorbed on the CNTs papers (1.7 s(-1)), and the process is more reversible with small redox peak separation of 23 mV This may be due to the synergetic promotion of CNTs and IL to electron transfer of the protein, especially the IL as the binder, showing better electrochemical properties than that of chitosan and Nafion. Furthermore, GOx adsorbed at the modified electrode exhibits good stability and keeps good electrocatalytic activity to glucose with broad linear range up to 20 mM. Besides, the simple preparation procedure and easy renewability make the system a basis to investigate the electron transfer kinetics and biocatalytic performance of GOx and provide a promising platform for the development of biosensors.

A third-generation H2O2 biosensor based on horseradish peroxidase-labeled Au nanoparticles self-assembled to hollow porous polymeric nanopheres

A novel third-generation biosensor for hydrogen peroxide (H2O2) was developed by self-assembling gold nanoparticles to hollow porous thiol-functionalized poly(divinylbenzene-co-acrylic acid) (DVB-co-AA) nanospheres. At first, a cleaned gold electrode was immersed in hollow porous thiol-functionalized poly(DVB-co-AA) nanosphere latex to assemble the nanospheres, then gold nanoparticles were chemisorbed onto the thiol groups of the nanospheres. Finally, horseradish peroxidase (HRP) was immobilized on the surface of the gold nanoparticles. The immobilized horseradish peroxidase exhibited direct electrochemical behavior toward the reduction of hydrogen peroxide. The resulting biosensor showed a wide linear range of 1.0 mu M-8.0 mM and a detection limit of 0.5 mu M estimated at a signal-to-noise ratio of 3. Moreover, the studied biosensor exhibited high sensitivity, good reproducibility, and long-term stability.

Direct electrochemical detection of glucose in human plasma on capillary electrophoresis microchips

We developed an electrochemical detector on a hybrid chip for the determination of glucose in human plasma. The microchip system described in this paper consists of a poly(dimethylsiloxane) (PDMS) layer containing separation and injection channels and an electrode plate. The copper microelectrode is fabricated by selective electroless deposition. The fabrication of the decoupler is performed by platinum electrochemical deposition on the metal film formed by electroless deposition. Factors influencing the performance, including detection potential, separation field strength, and buffer concentration, were studied. The electrodes exhibited good stability and durability in the analytical procedures. Under optimized detection conditions, glucose responded linearly from 10 muM to 1 mM. Finally, glucose in human plasma from three healthy individuals and two diabetics was successfully determined, giving a good prospect for a new clinical diagnostic instrument.

Single-wall carbon nanotube-based voltammetric sensor and biosensor

The pH-sensitive property of the single-wall carbon nanotube modified electrode based oil the electroactive group on the single-wall carbon nanotube was explored by differential pulse voltammetry technique. In pH range 1-13 investigated in Britton-Robinson (B-R) buffer, the anodic peak shifted negatively along with the increase of pH exhibiting a reversible Nernstian response. Experiments were carried out to investigate the response of the single-wall carbon nanotube (SWNT) modified electrode to analytes associated with pH change. The response behavior of the modified electrode to ammonia was studied as an example. The potential response could reach equilibrium within 5 min. The modified electrode had good operational stability. Voltammetric urease and acetylcholinesterase biosensors were constructed by immobilizing the enzymes with sol-get hybrid material. The maximum potential shift could reach 0.130 and 0.220V for urea and acetylthiocholine, respectively. The methods for preparing sensor and biosensor were simple and reproducible and the range of analytes could be extended to substrates of other hydrolyases and esterases.

A novel method to construct a third-generation biosensor: self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) nanospheres

A novel method for fabrication of horseradish peroxidase (HRP) biosensor has been developed by self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) (St-co-AA) nanospheres. At first, a cleaned gold electrode was immersed in thiol-functionalized poly(St-co-AA) nanosphere latex prepared by emulsifier-free emulsion polymerization of St with AA and function with dithioglycol to assemble the nanospheres, then gold nanoparticles were chemisorbed onto the thiol groups. Finally, horseradish peroxi- dase was immobilized on the surface of the gold nanoparticles. The sensor displayed an excellent electrocatalytical response to reduction of H2O2 without the aid of an electron mediator. The sensor was highly sensitive to hydrogen peroxide with a detection limit of 4.0 mumol l(-1), and the linear range was from 10.0 mumol l(-1) to 7.0 mmol l(-1). The biosensor retained more than 97.8% of its original activity after 60 days of use. Moreover, the Studied biosensor exhibited good current repeatability and good fabrication reproducibility.