The cytotoxicity of photoexcited CdS in an E. coli-CdS hybrid system and the roles of the sacrificial agent to reduce this toxic effect.

This study investigates the biosynthesis of CdS nanoparticles (NPs) by Escherichia coli CD-2 to develop an E. coli-CdS hybrid system. The hybrid system was exposed to light in the presence and absence of cysteine (Cys) as a sacrificial agent. The finding revealed that in the absence of Cys, photo-induced holes led to a sharp increase in oxidative stress, disrupting the oxidative/antioxidative balance within bacterial cells. Consequently, cellular components were oxidized under elevated oxidative stress, lending to functional loss. This oxidative damage resulted in reduced cell viability, and in severe cases, cell disruption. Fortunately, the inclusion of the sacrificial agent alleviated these toxic effects. Cys quenched the photo-induced holes, markedly lowering oxidative stress within the cells. This mitigation enabled the maintenance of essential cellular functions during treatment. The majority of bacterial cells preserved their vitality and utilized the extra photoelectrons for cell growth under these conditions.