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 gp 51, applied in the design of photoluminescence-based immunosensors, is proposed and discussed. Protein gp 51 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 gp 51 ( gp 51/TiO 2 /glass). After incubation of the gp 51/TiO 2 /glass in a solution containing anti- gp 51, a new structure (anti- gp 51/ gp 51/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 gp 51 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, gp 51/TiO 2 /glass and anti- gp 51/ gp 51/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.