Preparation Of Several Composited Nanomaterials And Their Application In Amperometric Enzyme Biosensors

Biosensor is a new analytical measurement, which combines several subjects such as medicine, physics, chemistry and biology. Meantime, because of its low cost, high sensitivity and simple preparation, biosensor has had important applications in some areas such as clinic medicine, environment measurement and food industry. And in 1967, the first glucose oxidase biosensor was prepared which attracted more and more interest in enzyme biosensors. The key technique of enzyme biosensors is the immobilization of enzyme, and this paper introduces some enzyme biosensors which combine the immobilization of enzyme and several nano-materials, and the main works are included as follows:1. Glucose Biosensor Based on Chitosan-nano Gold/nano-Prussian Blue/L-cysteine Modified Gold ElectrodeA novel glucose biosensor has been presented in this paper. L-cysteine was immobilized onto a gold electrode to form a positively charged surface, and nano-Prussian blue was assembled on the modified surface as an electron transfer mediator. Then, the hybrid film of chitosan-nano gold and glucose oxidase (GOD) was immobilized on the electrode to fabricate the proposed biosensor. The modifying process was characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry(CV) and transmission electron microscopy (TEM). And the effects of applied potential and pH on the response currents were also investigated. Under optimal conditions, the resulting biosensor displayed a rapid response to glucose and the linear range of the biosensor was from 3.0×10-6 to 1.0×10-3 mol/L with a detection limit of 1.6×10-6 mol/L (S/N=3). Moreover, the interferents influencing the proposed biosensor were researched in detail, and the biosensor possessed excellent selectivity and good stability.2. Immobilizing Pt Nanoparticles and Chitosan Hybrid Film on Polyaniline Nanofibers Membrane for an Amperometric Hydrogen Peroxide BiosensorA convenient and effective way for fabricating amperometric hydrogen peroxide (H2O2) biosensor was designed in this paper. Firstly, polyaniline (PANI) nanofibers membrane with good conductance and high surface area was electropolymerized on a gold electrode as a substrate to enhance the electron-transfer of the biosensor. Then, Pt nanoparticle (PtNP) was dispersed in PANI nanofibers membrane. Finally, the hybrid film containing negatively charged gold nanoparticle (AuNP), positively charged chitosan (CS) and horseradish peroxidase (HRP) was immobilized on the modified electrode to form a stable biofunctional film, which was also employed as an anti-interferent barrier and a protective layer to PtNP. The modifying process was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) and the morphology of the PANI nanofibers membrane was characterized by scanning electron microscopy (SEM). The proposed biosensor exhibited a rapid response to H2O2 and good selectivity to possible interferents, due to the enhanced electron-transfer kinetics and the sufficient selective permeability of the hybrid film. Under the optimized conditions, the linear range of the biosensor was from 1.4×10-5 to 1.5×10-2 mol/L with a detection limit of 7.2x10-6 mol/L (S/N=3). The Michaelies-Menten constant KMapp value was 1.28 mmol/L, suggesting a high affinity. Moreover, it displayed good reproducibility and long-term stability.3. A high sensitivity glucose biosensor based on immobilizing Pt nanoparaticle and glucose oxidase on the composite film of gold nanoparticle, carbon nanotube and chitosanA good conductive and large surface composite film of of gold nanoparticle, carbon nanotube and chitosan was proposed to prepare a highly sensitive and low detection limitary amperometric glucose biosensor in this paper. Firstly, the mixture of gold nanoparticle, carbon nanotube and chitosan was dripped on the glass carbon electrode to obtain a composite film with good conductance and high surface area. Then, Pt nanoparticle (PtNP) was deposited on this composite film. Finally, the glucose oxidase was immobilized on the modified electrode surface by covalent bond. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize each steps in the the modified progress. The proposed biosensor exhibited a rapid response time and high sensitivity to glucose. Under the optimized conditions, the linear range of the biosensor was from 6.0×10-7 to 3.5×10"3 mol/L with a low detection limit of 1.9×10-7 mol/L (S/N=3). The value of Michaelies-Menten constant was 0.39 mmol/L. Further more, the obtained electrode also exhibited a long-term life and good reproducibility.