Interaction mechanism between TiO2 nanostructures and bovine leukemia virus proteins in photoluminescence-based immunosensors

Abstract

In this research a mechanism of interaction between a semiconducting TiO₂ 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 TiO₂ thin film, formed on glass substrates (TiO₂/glass). A photoluminescence (PL) peak shift from 517 nm to 499 nm was observed after modification of the TiO₂/glass by adsorbed gp51 (gp51/TiO₂/glass). After incubation of the gp51/TiO₂/glass in a solution containing anti-gp51, a new structure (anti-gp51/gp51/TiO₂/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 TiO₂ surface. The strength of the electric field affecting the photoluminescence centers, was determined from variations between the PL-spectra of TiO₂/glass, gp51/TiO₂/glass and anti-gp51/gp51/TiO₂/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 TiO₂ after its protein modification reveals an understanding of the interaction mechanism between TiO₂ and proteins that is the key issue responsible for biosensor performance.