Studies on interaction of CdTe quantum dots with bovine serum albumin using fluorescence correlation spectroscopy

Luminescent quantum dots (QDs) have widely used in some biological and biomedical fields due to their unique and fascinating optical properties, meanwhile the interaction of QDs with biomolecules recently attract increasing attention. In this paper, we employed fluorescence correlation spectroscopy (FCS) to investigate the nonspecific interaction between CdTe QDs and bovine serum albumin (BSA) as a model, and evaluate their stoichiometric ratio and association constant. Our results documented that BSA was able to bind to CdTe QDs and form the QD-BSA complex by a 1:1 stoichiometric ratio. The association constant evaluated is 1.06+/-0.14x10(7) M(-1) in 0.01 M phosphate buffer (pH=7.4). Furthermore, we found that QD-BSA complex dissociated with increase of ion strength, and we speculated that the interaction of CdTe QDs with BSA was mainly attributed to electrostatic attraction. Our preliminary results demonstrate that fluorescence correlation spectroscopy is an effective tool for investigation of the interaction between quantum dots (or nanoparticles) and biomolecules.