Biosensors Based On Polyaniline And It's Composite Materials

A polyaniline/polyisoprene composite film with permselectivity was synthesized by electrochemical method for the first time, which can determine selectively H2O2 in the presence of electroactive interferent ascorbic acid. The SEM and electrochemical studies showed that the composite film exhibited more compact structure and lower electrochemical activity than polyaniline film. The glucose biosensor based on the polyaniline/polyisoprene composite film showed high selectivity. The sensor could eliminate the interference of electroactive ascorbic acid, and exhibited high operational and storage stability (No apparently difference in response of the biosensor was observed after been used continuously for 150 times and stored for 5 months). It was found that the composite film containing 28.6% polyisoprene suited well for biosensor construction. The apparent Michaelis constanst and activation energy for the immobilized glucose oxidase are 11.9 mM and 41.1 kJ-mol"1, respectively. The biosensor response was influenced by pH value of determined solution, applied potential and operational temperature.A novel method (in situ electropolymerization method) of biosensor elaboration was put forward. The method was carried out by in situ synthesizing a conducting polymer in a porous polymer film and co-immobilizing biomolecule in the composite film. It combined the advantages of porous polymer and electropolymerization method been used for biosensor construction, and the resulting biosensor exhibited not only high sensitivity but also good stability. The phenols, choline and glucose biosensors based on polyaniline/polyacrylonitrile composite films were prepared by this method.The phenol biosensor prepared by in situ electropolymerization showed excellent operational and storage stability. The sensor lifetime was 8 months, which is much better than that (in general 3 months) reported in literatures. The polymerization potential 0.48 V and 24% polyaniline in enzyme film were optimum parameters for the sensor construction. The working potential -50 mV and pH 6.5 suited well for the sensor operation. The activity of the phenol biosensor was inhibited by benzoic acid through reversible competitive inhibition mechanism and the inhibition constant is 33.8 U.M. The inhibition was influenced by pH value of the determined solution and increased with decreasing pH. In addition, the biosensor could be used for the detection of benzoic acid.The choline oxidase electrode based on polyaniline/polyacrylonitrile composite film showed sensitive and stable bioelectrochemical response to choline, which was influenced by pH, working potential and temperature. The apparentMichaelis constanst and activation energy for the immobilized glucose oxidase are 0.61 mM and 21.4 kJ-mol"', respectively. The kinetics analysis showed that the mass transport is partially rate-limiting. The glucose sensor prepared by in situ electropolymerization method exhibited rapid response (response time < 30 s), high sensitivity (67.1 mAM^cm"2), good selectivity (ascorbic acid, glutathione, L-cysteine and acetaminophen showed no interference to the detection of glucose), broad linear range (0.002-12 mM) and good detection limit (2 uM). The biosensor response kept unchanged after been used continuously for 100 times and stored for 100 days. The glucose sensor could be used for the detection of blood glucose and the results were very satisfactory.An amine oxidase-modified polyaniline electrode was formed by immobilization of amine oxidase in polyaniline film by electrochemical doping method. The enzyme electrode has a fast response (5~20s) for histamine and the reaction is controlled by the enzyme kinetics. The apparent Michaelis constanst, optimun pH and activation energy for the immobilized amine oxidase are 0.21 mM, 7.3-7.6 and 76 kJ-mol"1, respectively. The enzyme electrode exhibited good stability, which can be used for the determination of histamine. In addition, The electrochemical characteristics of the enzyme electrode were studied by cyclic volt...