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.

Some nanoparticles, such as quantum dots (QDs), are widely used in the biological and biomedical fields due to their unique optical properties. However, little is currently known about the interaction between these nanoparticles and biomolecules. Herein, we systemically investigated the interaction between chaperonin GroEL and water-soluble CdTe QDs based on fluorescence correlation spectroscopy (FCS), capillary electrophoresis, and fluorescence spectrometry. We observed that some water-soluble CdTe QDs were able to enter the inner cavity of GroEL and formed an inclusion complex after the activation of chaperonin GroEL with ATP. The inclusion of GroEL was size-selective to QDs and only small QDs were able to enter the inner cavity. The inclusion could suppress the fluorescence quenching of the QDs. Meanwhile, we evaluated the association constant between chaperonin GroEL and CdTe QDs by FCS. Our results further demonstrated that FCS was a very useful tool for study of the interaction of QDs and biomolecules.