Comparison of molecular interactions of Ag₂ Te and CdTe quantum dots with human serum albumin by spectroscopic approaches

Ag₂ Te quantum dots (QDs) have attracted great attention in biological applications due to their superior photoluminescence qualities and good biocompatibility, but their potential biotoxicity at a molecular biology level has been rarely discussed. In order to better understand the basic behavior of Ag₂ Te QDs in biological systems and compare their biotoxicity to cadmium-containing QDs, a series of spectroscopic measurements was applied to reveal the molecular interactions of Ag₂ Te QDs and CdTe QDs with human serum albumin (HSA). Ag₂ Te QDs and CdTe QDs statically quenched the intrinsic fluorescence of HSA by electrostatic interactions, but Ag₂ Te QDs exhibited weaker quenching ability and weaker binding ability compared with CdTe QDs. Electrostatic interactions were the main binding forces and Sudlow's site I was the primary binding site during these binding interactions. Furthermore, micro-environmental and conformational variations of HSA were induced by their binding interactions with two QDs. Ag₂ Te QDs caused less secondary structural and conformational change in HSA, illustrating the lower potential biotoxicity risk of Ag₂ Te QDs. Our results systematically indicated the molecular binding mechanism of Ag₂ Te QDs with HSA, which provided important information for possible toxicity risk of these cadmium-free QDs to human health.