Concentration-dependent binding of CdSe quantum dots on the SH3 domain

Quantum dots (QDs) are being used increasingly in applications for solar panels, consumer electronics, and biomedical imaging. For biomedical applications, QDs are typically coated with a biocompatible molecule for the system of interest. Experiments have indicated a QD dose-dependent and surface coating-dependent toxicity, with a portion of the toxicity being ascribed to interference with biomolecules. In this work, the interaction of trioctylphosphine oxide (TOPO) coated (CdSe)₁₃ QDs with the SRC homology 3 domain (SH3) protein domain are explored using molecular dynamics simulations. The results of this research agree well with experiments that show that at the lowest concentration, the QDs have little affinity for the native proline-rich motif (PRM) binding site of SH3. At higher concentrations, the QDs aggregate and increasingly prefer the PRM binding site, indicating that the normal SH3 function is impeded. This binding dependence is attributed to changes in the local density of the surface coated TOPO molecules upon aggregation. These results present possible interesting QD toxicity patterns and reveal the interdependence between dose and surface coating effects in QD toxicity.