Interaction mechanism between TiO(2) nanostructures and bovine leukemia virus proteins in photoluminescence-based immunosensors

In this research a mechanism of interaction between a semiconducting TiO(2) layer and bovine leukemia virus protein gp51, applied in the design of photoluminescence-based immunosensors, is proposed and discussed. Protein gp51 was adsorbed on the surface of a nanostructured TiO(2) thin film, formed on glass substrates (TiO(2)/glass). A photoluminescence (PL) peak shift from 517 nm to 499 nm was observed after modification of the TiO(2)/glass by adsorbed gp51 (gp51/TiO(2)/glass). After incubation of the gp51/TiO(2)/glass in a solution containing anti-gp51, a new structure (anti-gp51/gp51/TiO(2)/glass) was formed and the PL peak shifted backwards from 499 nm to 516 nm. The above-mentioned PL shifts are attributed to the variations in the self-trapped exciton energy level, which were induced by the changes of electrostatic interaction between the adsorbed gp51 and the negatively charged TiO(2) surface. The strength of the electric field affecting the photoluminescence centers, was determined from variations between the PL-spectra of TiO(2)/glass, gp51/TiO(2)/glass and anti-gp51/gp51/TiO(2)/glass. The principle of how these electric field variations are induced has been predicted. The highlighted origin of the changes in the photoluminescence spectra of TiO(2) after its protein modification reveals an understanding of the interaction mechanism between TiO(2) and proteins that is the key issue responsible for biosensor performance.