Characterization of the interaction between mercaptoethylamine capped CdTe quantum dots with human serum albumin and its analytical application

CdTe quantum dots (QDs) were synthesized in aqueous solution using 2-mercaptoethylamine hydrochloride (CA) as stabilizing agents. The interaction between CA-CdTe QDs with human serum albumin (HSA) was investigated by ultraviolet-visible (UV-vis) absorption, circular dichroism (CD), fluorescence and resonance Rayleigh scattering (RRS) spectroscopy. CD spectra revealed that the conformation and microenvironment of HSA were changed in the presence of CA-CdTe QDs. CA-CdTe QDs could strongly quench the intrinsic fluorescence of HSA by static quenching. The electrostatic interaction plays a major role in stabilizing the complex. The binding site number n and apparent binding constant K, corresponding thermodynamic parameters Delta G degrees, Delta H degrees and Delta S degrees at different temperatures were calculated. The interaction between CA-CdTe QDs and HSA led to the remarkable enhancement of RRS and the enchantments were in proportional to the concentration of HSA in the range 0.05 x 10(-7) to 4.0 x 10(-7) mol L(-1) and a detection limit of 4.2 x 10(-9) mol L(-1). Based on this, RRS methods to determinate HSA were developed. The influences of factors on the interaction between HSA with CA-CdTe QDs and some foreign substances were all examined, which showed that the method had a good sensitivity and selectivity. In addition, the reasons for the enhancement of RRS were investigated. (C) 2011 Elsevier B.V. All rights reserved.