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

Abstract The WO 3 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 p K a of nanostructured WO 3 film is estimated to be ∼2.74 using electrochemical method. The present WO 3 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 WO 3 surface with the redox formal potential ( E 0 ′) 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 WO 3 nanoparticles film, possibly due to the electrostatic interaction between WO 3 nanostructures and cyt. c , and processes its enzymatic activity toward H 2 O 2 . Based on these results, the third-generation biosensor for H 2 O 2 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—O 2 . The remarkable analytical advantages, as well as the characteristic of WO 3 nanoparticles film such as biocompatibility, low-cost, and facile to miniature give a strong basis for continuous, on-line detection of H 2 O 2 under pathophysiological conditions.