Systematically investigation of interactions between BSA and different charge-capped CdSe/ZnS quantum dots

Based on the unique properties, quantum dots (QDs) have been widely applied in biological and biomedical fields. However, relatively little is known about the interaction of QDs with some important biomolecules. In this study, the interactions between different charge-capped CdSe/ZnS QDs and bovine serum albumin (BSA) were systematically investigated by UV–vis absorption, fluorescence and circular dichroism (CD) spectroscopy under the physiological conditions. The negative mercaptoacetic acid (MAA) and positive cysteamine (CA) were used to synthesize CdSe/ZnS QDs with different surface charge. The results from fluorescence spectroscopy indicated that different charge-capped CdSe/ZnS QDs quenched the fluorescence intensity of BSA with different efficiency. The modified Stern–Volmer quenching constant Ka at different temperatures and the corresponding thermodynamic parameters ΔH, ΔG and ΔS were also calculated. The binding of QDs and BSA is a result of the formation of QDs–BSA complex and electrostatic interactions play a major role in stabilizing the complex. The circular dichroism technique was further used to analyze the conformational changes of BSA induced by QDs and the results indicated that the biological activity of BSA was affected by different charge-capped CdSe/ZnS QDs.