Toward development of optical biosensors based on photoluminescence of TiO₂ nanoparticles for the detection of Salmonella

Quality control of food and agriculture production is an inseparable part of human safety and well-being. Salmonella infections belong to one of the most monitored pathogens in the world, therefore advanced determination of this pathogen can decrease the risks of human diseases caused by this microorganism. In this research we introduce a novel optical immunosensor for determination of Salmonella typhimurium. The immunosensor is based on Titanium dioxide (TiO₂) nanoparticles deposited on glass substrates (glass/TiO₂). TiO₂ nanoparticles exhibit an intense photoluminescence (PL) in the visible range of spectrum at room temperature. The direct immobilization of antibodies (anti-S-Ab) against Salmonella antigens on the surface of glass/TiO₂ has resulted in the formation of glass/TiO₂/anti-S-Ab-based structure, which was characterized by increased PL intensity and IR-shifted position of the PL peak in comparison to the same characteristics of glass/TiO₂-based structure. The changes of the PL intensity and peak positions after interaction of the immobilized anti-S-Ab with Salmonella antigens (Salmonella-Ag) were used as immunosensor signal, allowing sensitive and selective detection of Salmonella-Ag in a label-free configuration. The sensitivity of the reported optical immunosensor towards Salmonella-Ag is in the range from 10³ to 10⁵ cell/ml. Some aspects of the interaction between TiO₂ and biological compounds have been discussed. This work opens up new possibilities for the development of optical label-free immunosensors suitable for fast, simple and efficient analysis of Salmonella infections.