WO3 nanostructures facilitate electron transfer of enzyme: Application to detection of H2O2 with high selectivity

The WO3 nanoparticles film is first employed as a support matrix for confining cytochrome c (cyt. c), an excellent model for studying electron transfer between the redox enzymes and the electrode. The surface pKa of nanostructured WO3 film is estimated to be ∼2.74 using electrochemical method. The present WO3 surface with negative charge at the neutral solution is very benefit for the adsorption of cyt. c with positive charge and facilitates electron transfer of cyt. c. As a result, direct and fast electron transfer of cyt. c is realized at the nanostructured WO3 surface with the redox formal potential (E0′) of −133.5 ± 1.7 mV (n = 4) versus Ag/AgCl and heterogeneous electron transfer rate constant of 5.57 ± 0.54 s−1. Experimental data indicate that cyt. c is stably confined onto the WO3 nanoparticles film, possibly due to the electrostatic interaction between WO3 nanostructures and cyt. c, and processes its enzymatic activity toward H2O2. Based on these results, the third-generation biosensor for H2O2 is developed with high selectivity, free from not only common anodic interferences like ascorbic acid, uric acid, 3,4-dihydroxyphenylacetic acid, and so on, but also cathodic interference—O2. The remarkable analytical advantages, as well as the characteristic of WO3 nanoparticles film such as biocompatibility, low-cost, and facile to miniature give a strong basis for continuous, on-line detection of H2O2 under pathophysiological conditions.