Development and characterization of a polypyrrole-based glucose biosensor

Abstract

Using in situ electrochemical polymerization of monomers that form electrically conducting polymers, one can control the thickness of the polymer film and the amount of enzyme that can be immobilized within the film. First, an investigation of the major parameters that influences the immobilization of glucose oxidase by entrapment in polypyrrole films, prepared by electropolymerization from aqueous solutions containing the enzyme and monomer, was carried out. For the electrochemical variables, which primarily govern mechanically stability of the films, even and adherent films were achieved by polymerization of 0.05 M pyrrole at the potentials ranging from 750 to 850 mV vs. Ag/AgCl. In the other hand, for the other parameters such as enzyme concentration, electrochemical growth of the films was found to be significantly inhibited by the presence of increasing amount of enzyme in the deposition solution. Scanning electron micrographs revealed that the morphology of the film was drastically changed by the enzyme concentration, indicating that much rougher surface of the film was obtained at lower concentration of enzyme. As an ultimate effect of the change in the film property, the permeability of the resulting film was found to decrease with increasing enzyme concentration in the deposition solution. Secondly, the polymerization conditions were examined to maximize the response of the resulting biosensor. It was found that the response was critically dependent on both the enzyme concentration and the film thickness and that there were several suboptimal sets of above parameters, which offer maximum responses. When polymerized at the enzyme concentration of 0.5 mg/ml, the optimum thickness of the film was observed to be 250 mC/㎠. In the other hand, when deposited at 5.0 mg/ml, the optimum thickness was about 10 mC/㎠. Furthermore, the sensitivity of biosensor was enhanced by preparing thicker film at lower enzyme concentration, confirming the dependence of the film...