Surface engineering of quantum dots for in vivo imaging.

The aim of this study was to investigate the effect of gluconic acid (GA) conjugation on the biodistribution of cysteamine-capped quantum dots (amino-QDots) in vivo. Cadmium selenide/zinc sulfide (CdSe/ZnS) was capped with cysteamine through a thiol exchange method, and different amounts of GA were conjugated to the amine groups of cysteamine via the formation of an amide bond. The emission maxima of the synthesized QDots, the amino-QDots and the GA-conjugated amine-QDots (GA-QDots) were located at 720, 600 and 610 nm, respectively. In the cell viability studies, the GA-QDots showed very low toxicity against CHO cells as compared to the cytotoxicity of the amino-QDots. The QDots were next intravenously injected into normal mice and then we performed ex vivo optical imaging. The majority of the amino-QDots were accumulated in the lung. In contrast, the GA-QDots were cleared out of the body through the kidney. Therefore, we expect that the conjugation of GA onto the amino-QDots can create opportunities for using amino-QDots for in vivo imaging.