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|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 O₂^{{radical dot} -} dismutation, offers great potential for contriving a third-generation O₂^{{radical dot} -} biosensor.