Ligand Effects on Selective Interaction of CdTe Quantum Dots with BSA

Five water-soluble CdTe quantum dots(QDs) were synthesized using thioglycolic acid(TGA),3-mercaptopropionicacid(MPA),1-thioglycerol(TG),L-cysteine(L-cys) and glutathione(GSH) as stabili-zers,respectively.The interaction of CdTe QDs with bovine serum albumin(BSA) was studied by UV-Vis absorptionand photoluminescence spectroscopy.Experimental results demonstrated that fluorescence of BSA could be markedly quenched by all these five CdTe QDs in Tris-HCl buffer solution(pH=7.40).The quenchingability of CdTe QDs to BSA is as GSHL-cysTGATGMPA in the order of ligands.However,when BSA was added into CdTe QDs solution,five CdTe QDs exhibited apparently selective responses to BSA.As the concentration of BSA increased,fluorescence intensity of CdTe QDs capped by TGA and MPA were both significantly enhanced firstly,then declined sharply.Under the same experimental conditions,fluore-scenceintensity of L-cys-capped CdTe QDs was significantly quenched by BSA,and that of TG-capped CdTe QDs was only slightly quenched by BSA.While almost no change of GSH-capped QDs fluorescence was observed in the presence of BSA.These results indicated that ligand molecular structure of CdTe QDs played an important role in the interaction between BSA and CdTe QDs.Time-resolved luminescence dynamics suggested that the ground state complex of BSA and CdTe QDs could form by electrostatic interaction.Possible interaction mechanism of BSA with CdTe QDs was proposed based on the molecular structure of ligands.