Detection of Extracellular H2O2 Released from Human Liver Cancer Cells Based on TiO2 Nanoneedles with Enhanced Electron Transfer of Cytochrome c

The high conductive TiO2 nanoneedles film is first employed as a support matrix for immobilizing model enzyme, cytochrome c (cyt c) to facilitate the electron transfer between redox enzymes and electrodes. Reversible and direct electron transfer of cyt c is successfully achieved at the nanostructured TiO2 surface with the redox formal potential (E-0') of 108.0 +/- 1.9 mV versus Ag|AgCl and heterogeneous electron transfer rate constant (k(s)) of 13.8 +/- 2.1 s(-1). Experimental data indicate that cyt c is stably immobilized onto the TiO2 nanoneedles film and maintains inherent enzymatic activity toward H2O2. On the basis of these results, the cyt c-TiO2 nanocomposits film is capable of sensing H2O2 at a suitable potential, 0.0 V (vs Ag|AgCl), where not only common anodic interferences like ascorbic acid, uric acid, 3,4-dihydroxyphenylacetic acid but also a cathodic interference, 02, are effectively avoided. Besides high selectivity, the present biosensor for H2O2 shows broad dynamic range and low detection limit. These remarkable analytical advantages, as well as the characteristic of TiO2 nanoneedles film such as high conductivity, biocompatibility, and facile ability to miniaturize establishes a novel approach to detection of extracellular H2O2 released from human liver cancer cells.