Protein Adsorption on Nanocrystalline TiO2 Films: An Immobilization Strategy for Bioanalytical Devices

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Abstract
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 °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-μm-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.