The magnetic nanoparticles modified with carboxyl functional group were synthesized and characterized. These nanoparticles covalently bound with hepatitis B surface antibody（HBsAb）, were used to detect hepatitis B surface antigen （HBsAg） in immunovoltammetry. The detection limit was found to be 0.06 ng/mL, which is much higher than that of enzyme-linked immunosorbent assay （ELISA） used in clinical analysis.
A Pt-nanooarticle/carbon nanotube modified graphite electrode immobilized with cholesterol oxidase/sol＇-gel layer was developed for monitoring cholesterol.Using this electrode,cholesterol concentration（4.0×10^-6 tp 1.0×10^-4mol/L）could be determined accurately in the presence of ascorbic or uric acid,and the response time was rapid （〈 20 s）. This biosensor has high sensitivity and selectivity.
A composite polymer carbon fiber electrode modified with Nafion and cellulose acetate is described. The modified electrode discriminates against both anionic reactants and big molecular organic compounds. The bilayer configuration is prepared in two steps. First, the carbon fiber electrode is coated with Nation, men followed by air evaporation of the solvent, me electrode is dipped in a cellulose acetate solution and hydrolyzed for a selected time. The permeability of the film is explored by use of rotating disk electrode measurements. Parameters affecting the film electrochemistry are investigated. The resulting electrodes show high selectivity and stability in body fluids. For in-vivo voltammetry, the composite polymer modified electrode has been used for detection of me oxidative current of neurotransmitter dopamine in rat brain, while it inhabits the oxidation of an°C neurotransmitter metabolites and some electroactive compounds.
