Effect of refluxed silver nanoparticles on inhibition and enhancement of enzymatic activity of glucose oxidase

Glucose oxidase was immobilized on the surface of silver nanoparticles. The enzymatic activity of the glucose oxidase was determined by the refluxing time of silver nanoparticles. In a short refluxing time, the silver nanoparticles behaved to inhibit the enzymatic activity of the glucose oxidase. However, the inhibitory effect of silver nanoparticles reduced along with the refluxing time. And an enhancement effect appeared as the silver nanoparticles were refluxed in a certain period of time. When the refluxing time of silver nanoparticles was 3.0 h, the enzymatic activity of the immobilized glucose oxidase reached the maximum value, which was almost 4-fold as compared with that of the native glucose oxidase. Fluorescence and circular dichroism spectra indicated that the glucose oxidase on the surface of silver nanoparticles changed its conformation, and the conformation change depended on the refluxing time of silver nanoparticles, which was probably due to different interactions between glucose oxidase and silver nanoparticles. (C) 2009 Elsevier B.V. All rights reserved.