Protein adsorption on nanocrystalline TiO2 films:: An immobilization strategy for bioanalytical devices

We have investigated the use of optically transparent, nanoporous TiO2 films as substrates for protein immobilization. Immobilization on such films may be readily achieved from aqueous solutions at 4 degrees C. The nanoporous structure of the film greatly enhances the active surface area available for protein binding (by a factor of 150 for a 4-mu m-thick film). We demonstrate that the redox state of immobilized cytochrome c may be modulated by the application of an electrical bias potential to the TiO2 film and that the fluorescence yield of immobilized fluorophore-labeled maltose-binding protein may be used to monitor specifically maltose concentration. We conclude that nanoporous TiO2 films may be useful both for basic studies of protein/electrode interactions and for the development of array-based bioanalytical devices employing both optical and electrochemical signal transduction methodologies.