Kumaran Ramanathan

Covalent immobilization of glucose oxidase to poly(O-amino benzoic acid) for application to glucose biosensor

A biosensor for glucose utilizing glucose oxidase (GOX) covalently coupled to poly(o-amino benzoic acid) (PAB; a carboxy-group-functionalized polyaniline) is described. Amperometric response measurements conducted via unmediated and mediated (with ferrocene carboxylic acid and tetrathiafulvalene) reoxidation of GOX show that glucose can be detected over a wide range of concentrations. An enzyme-conducting polymer-mediator model provides for better charge transport in a biosensor. The optimal response, obtained at pH 5.5 and 300 K, lies in the 1–40 mM range. A kinetic plot yields the value of the apparent Michaelis–Menten constant, Kmapp. The operational stability of the PAB-based glucose biosensor was experimentally determined to be about 6 days.

Application of polyaniline-Langmuir-Blodgett films as a glucose biosensor

Langmuir-Blodgett films of the polyemeraldine base form of polyaniline (PANI) have been successfully deposited on an indium tin oxide (ITO) coated glass surface. The enzyme glucose oxidase (GOX) was entrapped between the layers of the Langmuir-Blodgett (LB) film. The immobilized GOX was tested for retention of its catalytic activity and its ability to perform like a reagentless glucose biosensor. The electroactivity of such PANI-LB-GOX electrodes was tested using cyclic voltammetry (CV). On the basis of the anodic peak current at 0.7 V with respect to Ag/AgCl, a calibration curve for a PANI-LB-GOX based glucose biosensor was obtained.

Application of poly(aniline) as a glucose biosensor

Abstract The concentration dependence of glucose on solution-cast poly(aniline) films containing physically absorbed glucose oxidase has been amperometrically measured as a function of temperature (10–90 °C). It has been shown that such poly(aniline)-glucose oxidase electrodes are stable up to 77 °C and can be efficiently operated up to 25 mM of glucose solution. Besides this, an attempt has also been made to characterize the poly(aniline)-glucose oxidase electrode using UV-Vis and FTIR spectrometry and differential scanning calorimetry (DSC) techniques.

Enhanced loading of glucose oxidase on polyaniline films based on anion exchange

The temporal aspects of anion self-exchange in electrochemically prepared polyaniline films have been experimentally investigated. The exchange of bulkier tosylate-ferricyanide ion with Cl ion has been monitored by photometry and electrochemical techniques. The relative changes in porosity brought about by self-exchange have been experimentally determined to be 323 and 2125/k in tosylate-exchanged and ferricyanide-exchanged polyaniline films, respectively. Scanning electron microscopy has been used to delineate the surface morphology of polyaniline films. It is seen that the polyaniline films exhibit enhanced loading of glucose oxidase after a self-ion exchange, and, hence, they can be used for the fabrication of a third-generation glucose biosensor.

Dielectric spectroscopic studies on polypyrrole glucose oxidase films

An investigation was made into the dielectric spectroscopic characteristics of p-toluene sulfonate (PTS) doped polypyrrole (PPY) films in the presence and absence of immobilized glucose oxidase (GOX) in three different configurations : Al-PTS-PPY-Al, Al-PTS-PPY/GOX-Al, and Al-PTS-PPY/GOX/β-D-glucose-Al, respectively. Measurement of dielectric loss and capacitance yielded valuable information about the dielectric properties of GOX immobilized in PTS doped PPY films. The effect of both the temperature and varying β-D-glucose concentrations on the mobility of the charge carriers in these films was also systematically studied.

Immobilization and Characterization of Lactate Dehydrogenase on TEOS Derived Sol-Gel Films

Physical adsorption and physical entrapment techniques have been utilized for the immobilization of lactate dehydrogenase (LDH) on tetraethylorthosilicate (TEOS) derived sol-gel films. The enzyme (LDH) activity has been assayed as a function of time, temperature, pH and pyruvate concentration. The results of photometric measurements used for monitoring the reaction yield a response time of about 1 min, linearity over a concentration range of 0–1.5 × 10-3 M and detection limit of 5 × 10-5 M. The TEOS sol-gel films containing LDH have been found to be stable for about 30 days at temperatures 4 to 10°C.

Ordering of a lateral crown ether and terminal short POE chains in some symmetrical nematogens by 13 C NMR

A lateral crown ether fragment can be introduced on symmetrical mesogens containing only three aromatic rings. The replacement of the terminal alkoxy chains by chains containing oxyethylene units decreases the melting and clearing temperatures allowing one to obtain nematic compounds near room temperature. These compounds dissolve LiBF4 salt only to a small extent, but the nematic arrangement, is thereby destroyed. The carbon chemical shift anisotropy and the local C-H bond order parameters were obtained for the nematic phase for the crown ether fragment and the terminal chains. This study indicates that the crown ether average conformation changes insignificantly on decreasing the temperature. The lateral crown ether protrudes markedly from the core with the consequence that the molecular shape is far from rod-like in geometry.

Simulation of Electrochemical Process for Glucose Oxidase Immobilized Conducting Polymer Electrodes

Abstract Computer simulation of electrochemical processes that govern the operation of conducting polymer modified electrodes (CPME) have been reported in this paper. Comparison of the behaviour of a biocatalyst (GOX) in free solution and in the immobilized phase in conducting polymer modified electrodes (CPME) has been provided The output has been obtained using the Runga Kutta numerical method solved by programming in FORTRAN 77. The results point out that the catalytic current generated by an immobilized enzyme in layer is larger as compared to that for the enzyme in solution, and that it varies with the thickness of the diffusion layer.