Biofunctional Titania Nanotubes for Visible-Light-Activated Photoelectrochemical Biosensing

The photoelectrochemical detection method is a newly developed and promising analytical method for biosensing. In this work, photoactive TiO2 nanotubes (FNs) immobilized with horseradish peroxidase (HRP) were prepared and used for visible-light-activated photoelectrochemical detection of H2O2. TNs were fabricated by anodic oxidation of titanium substrate and possessed large surface areas, good uniformity and conformability, and high porosity, which were favorable for enzyme immobilization. Electrochemical and UV-vis spectroscopic measurements demonstrated that TNs provided excellent matrixes for the adsorption of HRP and the adsorbed HRP effectively retained its bioactivities. The photocurrent spectra of HRP/TNs showed an obvious photocurrent response under visible-light irradiation (lambda >= 400 nm), suggesting the possibility of photoelectrochemical detection of H2O2 upon visible-light irradiation. It was found that the generated photocurrent of HRP/TNs at 400 nm was significantly enhanced after the addition of H2O2 in solution and the photocurrent intensity increased with the increase of the H2O2 concentration. The HRP/TNs electrode displayed a linear range of 5.0 x 10(-7)-3.5 x 10(-5) M and a low detection limit of 1.8 x 10(-7) M for H2O2 determination. Thus, the protein-immobilized TNs would be expected to be a novel photoactive material for photoelectrochemical biosensing. This proposed strategy may open a new avenue for the applications of nanotubular TiO2 in visible-light-activated photoelectrochemical biosensing, which could largely reduce the destructive effect of UV light and the photoholes generated by illuminated TiO2 to biomolecules.