Studies On Chitosan Modified Electrodes For Bioanalysis

Biopolymer chitosan(CS)is a polysaccharide derived by deacetylation of chitin,which has been widely used in scientific and industrial fields due to its excellent properties such as biocompatibility, biodegradability,ability to form films,and high reactivity.CS is usually used as a matrix to immobilize biomolecules to construct biosensors such as enzyme electrodes.In this thesis,we have briefly reviewed the recent research progress for CS and relevant enzyme electrodes,and conducted the following researches.1.A chitosan-Cu²⁺composite film modified Au electrode was prepared through the compleximetric adsorption of Cu²⁺on chitosan,and glucose oxidase was further compleximetrically adsorbed on the chitosan-Cu²⁺composite film through metal-protein complexation for fabricating an enzyme electrode.The biosensor exhibited a linear range from 0.03 to 2.5 mmol L^-1for glucose sensing,with a linear correlation coefficient of 0.997 and a detection limit of 1μmol L^-1 (S/N=3).Various modification processes for the enzyme electrode were monitored by the electrochemical quartz crystal microbalance (EQCM)technique.2.Chitosan crosslinked by p-quinone was proposed to immobilize glucose oxidase(GOD)to develop a new GOD-based glucose biosensor.The biosensor exhibited a linear range from 0.001 to 2 mmol L^-1for glucose sensing,with a linear correlation coefficient of 0.999.3.Chitosan-dopamine and chitosan-dopamine-multiwalled carbon nanotubes composites were prepared by covalently linking the amino groups of dopamine and chitosan with glutaraldehyde,which was characterized by FTIR and UV-VIS spectra.The composite modified Au electrode with well-defined quinone redox peaks effectively mediated the oxidation of NADH in pH 7.0 phosphate buffer,with an overpotential decrease by ca.500 mV(vs.bare Au),a limit of detection of 65 nmol L^-1.