Abstract: Novel enzyme multilayer films on the surface of polystyrene(PS) colloid particles was fabricated by layer-by-layer(LbL) self-assembly. Superoxide dismutase(SOD) was adsorbed on the PS particles as either polycation or polyanion switched by adjusting pH alternatingly with the oppositely charged polyelectrolytes. zeta-Potential and TEM results indicated the regular and stepwise growth of the multilayer structure. The amount of the immobilized SOD was estimated from the difference in SOD bioactivity of the supernatant after adsorption and SOD solution before adsorption by using the pyrogallol oxidation method. The immobilization amount of SOD was 12 and 51 IU when adsorbed in pH=8.0 as a polyanion and in pH=4.3 as a polycation, respectively. However, the relative activity of the former was 23.4% while that of the latter was 2.9%, compared to that of free SOD in aqueous solution. Anionic SOD was found to form more regular and smooth layers on the PS particle surface and cationic SOD to aggregate. By adjusting pH of the adsorption solution we can optimize the assembled status and bioactivity of particle-immobilized enzyme.

Key words: Superoxide dismutase(SOD), Layer-by-layer self-assembly, Immobilized enzyme, Polyelectrolyte multilayer films, PS colloid particle