Optimizing immobilization of avidin on surface-modified magnetic nanoparticles: characterization and application of protein-immobilized nanoparticles.

Abstract

A simple optimization method of immobilization of avidin on magnetic nanoparticles (MNPs)' surface was proposed in this study. The avidin-immobilized MNPs were then developed and used to immobilize a model enzyme [Horseradish peroxidase (HRP)]. The loading capacity (LC) and activity of avidin-immobilized MNPs were optimized through selecting the most appropriate nanoparticle's size and shape, glutaraldehyde concentration, cross-linking reaction time, ultrasonic processing time, and initial concentration of avidin. The LC under optimized conditions was 63.37±1.29mg avidin/g MNPs, and the immobilized protein was still able to maintain its high biological activity of 10.86±0.13 U/mg (biotin-binding activity of nature avidin was 14.1U/mg) and better thermal stability compared to free avidin. A highly reusable, stable, and easily recovered immobilized HRP was obtained using MNPs as carriers. The immobilized HRP was reused repeatedly more than 9 times and retained more than 65% of its original activity.