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

We have investigated the use of optically transparent, nanoporous TiO2 film s as substrates for protein immobilization. Immobilization on such films ma y be readily achieved from aqueous solutions at 4 degrees C. The nanoporous structure of the film greatly enhances the active surface area available f or protein binding (by a factor of 150 for a 4-mu m-thick film). We demonst rate that the redox state of immobilized cytochrome c may be modulated by t he application of an electrical bias potential to the TiO2 film and that th e fluorescence yield of immobilized fluorophore-labeled maltose-binding pro tein 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 bioanalytica l devices employing both optical and electrochemical signal transduction me thodologies.