Protein adsorption on nanoporous TiO2 films: a novel approach to studying photoinduced protein/electrode transfer reactions

Abstract

We have investigated the use of nanoporous Ðlms as substrates for protein TiO 2 immobilisation. Such Ðlms are of interest due to their high surface area, optical transparency, electrochemical activity and ease of fabrication. These Ðlms moreover allow detailed spectroscopic study of protein/electrode electron transfer processes. We Ðnd that protein immobilisation on such Ðlms may be readily achieved from aqueous solutions at 4 ¡C with a high binding stability and no detectable protein denaturation. The nanoporous structure of the Ðlm greatly enhances the active surface area available for protein binding (by a factor of up to 850 for an 8 lm thick Ðlm). We demonstrate that the redox state of proteins such as immobilised cytochrome-c (Cyt-c) and haemoglobin (Hb) may be modulated by the application of an electrical bias potential to the Ðlm, without the TiO 2 addition of electron transfer mediators. The binding of Cyt-c on the Ðlms is TiO 2 investigated as a function of Ðlm thickness, protein concentration, protein surface charge and ionic strength. We demonstrate the potential use of immobilised Hb on such TiO 2 Ðlms for the detection of dissolved CO in aqueous solutions. We further show that protein/electrode electron transfer may be initiated by UV bandgap excitation of the TiO 2 electrode. Both photooxidation and photoreduction of the immobilised proteins can be achieved. By employing pulsed UV laser excitation, the interfacial electron transfer kinetics can be monitored by transient optical spectroscopy, providing a novel probe of protein/electrode electron transfer kinetics. We conclude that nanoporous Ðlms may TiO 2 be useful both for basic studies of protein/electrode interactions and for the development of novel bioanalytical devices such as biosensors.

Nitric Oxide Biosensors Based on the Immobilization of Hemoglobin on Mesoporous Titania Electrodes

“…However, like our optical CO biosensor described previously [19], it shows the viability of the approach.…”

Immobilization and Electrochemistry of Negatively Charged Proteins on Modified Nanocrystalline Metal Oxide Electrodes

“…The relatively slow timescale for the protein adsorption is attributed to slow protein diffusion through the film pores, as we have discussed previously [1]. The solutions comprised the protein of interest (Cyt-c: 20 mM or, GFP: 40 mM, ferredoxin: 15 mM) and 0.01 M phosphate buffer (pH 7).…”

Direct Electrochemistry and Electrocatalysis of Hemoglobin–TiO2 Whisker Film Modified Glassy Carbon Electrode

“…Besides, the mesoporous titania support has a special whisker morphology where protein adsorption can be readily achieved with high binding stability [14]. In addition, the titanium dioxide (TiO 2 ) possess the high reactivity and the specific ability to advance photochemical applications, and can efficiently separate photogenerated charges facilitating some redox chemical reactions with attached biomolecules [15].…”