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 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.

Enhanced response induced by polyelectrolyte-functionalized ionic liquid in glucose biosensor based on sol-gel organic-inorganic hybrid material

In this work, a polyelectrolyte-functionalized ionic liquid (PFIL) was firstly incorporated into a sol-gel organic-inorganic hybrid material (PFIL/sol-gel). This new composite material was used to immobilize glucose oxidase on a glassy carbon electrode. An enhanced current response towards glucose was obtained, relative to a control case without PFIL. In addition, chronoamperometry showed that electroactive mediators diffused at a rate 10 times higher in the apparent diffusion coefficient in PFIL-containing matrices. These findings suggest a potential application in bioelectroanalytical chemistry.

Room temperature ionic liquid doped DNA network immobilized horseradish peroxidase biosensor for amperometric determination of hydrogen peroxide

A novel electrochemical H2O2 biosensor was constructed by embedding horseradish peroxide (HRP) in a 1-butyl-3-methylimidazolium tetrafluoroborate doped DNA network casting on a gold electrode. The HRP entrapped in the composite system displayed good electrocatalytic response to the reduction of H2O2. The composite system could provide both a biocompatible microenvironment for enzymes to keep their good bioactivity and an effective pathway of electron transfer between the redox center of enzymes, H2O2 and the electrode surface. Voltammetric and time-based amperometric techniques were applied to characterize the properties of the biosensor. The effects of pH and potential on the amperometric response to H2O2 were studied. The biosensor can achieve 95% of the steady-state current within 2 s response to H2O2. The detection limit of the biosensor was 3.5 mu M, and linear range was from 0.01 to 7.4 mM. Moreover, the biosensor exhibited good sensitivity and stability. The film can also be readily used as an immobilization matrix to entrap other enzymes to prepare other similar biosensors.

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.

The modification of screen-printed carbon electrodes with amino group and its application to construct a H2O2 biosensor

Electrooxidation of thionine on screen-printed carbon electrode gives rise to the modification of the surface with amino groups for the covalent immobilization of enzymes such as horseradish peroxidase (HRP). The biosensor was constructed using multilayer enzymes which covalently immobilized onto the surface of amino groups modified screen-printed carbon electrode using glutaraldehyde as a bifunctional reagent. The multilayer assemble of HRP has been characterized with the cyclic voltammetry and the faradaic impedance spectroscopy. The H2O2 biosensor exhibited a fast response (2 s) and low detection limit (0.5 muM).

Specific determination of As(V) by an acid phosphatase-polyphenol oxidase biosensor

An original amperometric biosensor based on the simultaneous entrapment of acid phosphatase (AcP) and polyphenol oxidase (PPO) into anionic clays (layered double hydroxides) was developed for the specific detection of As(V). The functioning principle of the bienzyme electrode consisted of the successive hydrolysis of phenyl phosphate into phenol by AcP, followed by the oxidation of phenol into o-quinone by PPO. The phenyl phosphate concentration was, thus, monitored by potentiostating the biosensor at -0.2 V vs Ag/AgCl to detect amperometrically the generated quinone. The detection of As(V) was based on its inhibitory effect on AcP activity toward the hydrolysis of phenyl phosphate into phenol. The As(V) can be specifically determined in pH 6.0 acetate buffer without any interferences of As(III) or phosphate, the detection limit being 2 nM or 0.15 ppb after an incubation step for 20 min.

Facile preparation of amperometric laccase biosensor with multifunction based on the matrix of carbon nanotubes-chitosan composite

The carbon nanotubes-chitosan (CNTs-CS) composite provides a suitable biosensing matrix due to its good conductivity, high stability, and good biocompatibility. Enzymes can be firmly incorporated into the matrix without the aid of other cross-linking reagents. The composite is easy to form insoluble film in solution above pH 6.3. Based on this, a facilely fabricated amperometric biosensor by entrapping laccase into the CNTs-CS composite film has been developed. At pH 6.0, the fungi laccase incorporated into the composite film remains better catalytic activity than that dissolved in solution. The system is in favor of the accessibility of substrate to the active site of laccase, thus the affinity to substrates is improved greatly, such as 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS), catechol, and 0, with K. values of 19.86 mu M, 9.43 mu M, and 3.22 mM, respectively. The major advantages of the as-prepared biosensor are: detecting different substrates (ABTS, catechol, and 02), possessing high affinity and sensitivity, durable long-term stability, and facile preparation procedure. On the other hand, the system can be applied in fabrication of biofuel cells as the cathodic catalysts based on its good electrocatalysis for oxygen reduction.

Electrogenerated chemiluminescence biosensor based on Ru(bpy)(3)(2+) and dehydrogenase immobilized in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) composite material

A new electrogenerated chemiluminescence biosensor was fabricated by immobilizing ECL reagent Ru(bPY)(3)(2+) and alcohol dehydrogenase in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) (PSS) organically modified composite material. The component PSS was used to immobilize ECL reagent Ru(bpy)(3)(2+) by ion-exchange, while the addition of chitosan was to prevent the cracking of conventional sol-gel-derived glasses and provide biocompatible microenvironment for alcohol dehydrogenase. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate and it was much simpler than previous double-layer design. The detection limit was 9.3 x 10(-6) M for alcohol (S/N = 3) with a linear range from 2.79 x 10(-5) to 5.78 x 10(-2) M. With ECL detection, the biosensor exhibited wide linear range, high sensitivity and good stability.

Self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) nanospheres for fabrication of a mediatorless biosensor

A novel strategy to construct a sensitive mediatorless sensor of H2O2 was described. At first, a cleaned gold electrode was immersed in thiol-functionalized poly(styrene-co-acrylic acid) (St-co-AA) nanosphere latex prepared by emulsifier-free emulsion polymerization St with AA and function with dithioglycol to assemble the nanospheres, then gold nanoparticles were chemisorbed onto the thiol groups and formed monolayers on the surface of poly(St-co-AA) nanospheres. Finally, horseradish peroxidase (HRP) 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 biosensor showed a linear range of 8.0 mu mol L-1-7.0 mmol L-1 with a detection limit of 4.0 mu mol L-1. The biosensor retained more than 97.8% of its original activity after 60 days' storage. Moreover, the studied biosensor exhibited good current reproducibility and good fabrication reproducibility.