Direct electron transfer of superoxide dismutase promoted by high conductive TiO2 nanoneedles

Direct electron transfer (DET) between copper, zinc-superoxide dismutase (Cu, Zn-SOD) and electrode is first studied by using the high conductive TiO2 nanoneedles film as a support matrix to immobilize Cu, Zn-SOD. The cyclic voltammogram of SOD adsorbed on TiO2. nanoneedles shows a pair of quasi-reversible redox peaks with an apparent formal potential (E-0) of 369.0 +/- 5.4 mV versus Ag vertical bar AgCl in phosphate buffer solution (PBS, pH 7.0) and heterogeneous electron rate constant (k(s)) of 4.6 +/- 0.5 s(-1). UV-vis spectroscopic data and electrochemical results testify that nanostructured TiO2 matrix is sure of improving SOD loading with the retention of bioactivity and greatly promote DET for its high specific surface area, stability and biocompatibility. Therefore, the virtues of TiO2 nanoneedles for promoting DET of SOD, provided with specific electrocatalytical activity toward O-2(center dot-) dismutation, offers great potential for contriving a third-generation O-2(center dot-) biosensor. (c) 2008 Elsevier B.V. All rights reserved.