Influence of mercaptopropionic-acid-capped CdTe quantum dots on the human chorionic gonadotropin structure and activity alterations

As an emerging nanomaterial, quantum dots (QDs) have received enormous attention for their excellent photophysical properties. However, their biotoxicity restricts the application and development of quantum dots. To evaluate the toxicity of quantum dots at the molecular level, the effects of quantum dots on human chorionic gonadotropin (hCG) were explored using spectroscopic techniques and isothermal titration calorimetry (ITC). It was demonstrated that MPA (mercaptopropionic acid)-CdTe QDs interacted with hCG through hydrogen bonds and van der Waals interactions, causing a decrement in the α-helix of the protein and an unfolding process. The conformational changes of hCG lead to the damage of hydrogen bonding networks and the exposure of tyrosine residues to the surface of hCG, which might be the reason why the hCG fluorescence intensity increased and the bioactivity decreased with the increasing concentration of MPA-CdTe QDs.