Studies Of Biosensors Based On Superoxide Dismutase

Three kinds of novel superoxide dismutase(SOD)electrodes(SOD/Cys/sol-gel, SOD/Cys/AuNP and SOD/Cys/AuNP/sol-gel) were developed by combining self-assembled monolayers (SAMs), nanotechnology and sol-gel technology. The effect of pH and scan rate on the peak current and peak potential of SOD electrodes and their stability were studied systematically. The preparation conditions were optimized. The SOD electrodes were used to respond to superoxide anion, which was prepared by DMSO/NaOH and xanthine/xanthine oxidase systems. The faster electron transfer rate of SOD electrodes with higher sensibility and excellent stability in the presence of L-cysteine and catalysis of Au nanoparticles was testified. The sol-gel film can not only immobilize SOD efficiently, but also maintain its reactivity well. The current ratio of the cathodic peak current to the anodic one of the SOD/Cys/AuNP/sol-gel electrode (i_pc/i_pa=1.1 at 100mV s^-1) and the separation between the anodic and cathodic peak potentials (ΔE_p=E_pa-E_pc=0.24 V at 100mVs^-1) indicate that the electrode process of SOD is quasi-reversible. The formal potential, estimated as (E_pa+E_pc)/2, was 110mV (versus SCE). The heterogeneous electron transfer rate constant was evaluated to be about 10.3 s^-1. The reactivity of electrode, which was stored after sixty days, maintained 97%. Making use of good qualities of the SAMs, nanotechnology and sol-gel technology, the superoxide dismutase immobilized by thin silica sol-gel film in the presence of L-cysteine and Au nanoparticles on gold electrode surface can be developed with higher sensibility and excellent stability.