Preparation of Cu-doped CdS quantum dots coated with biocompatible carboxymethyl chitosan for near infrared fluorescence imaging

In this study, water soluble Cu-doped CdS quantum dots (Cu:CdS QDs) were synthesized by one-pot method. The effect of reaction conditions on the Cu:CdS QDs were studied systematically, and the Cu:CdS QDs synthesized under optimizing condition possessed a small size (∼4 nm), high luminance and good self-fluorescence performance. Compared with CdS QDs, the fluorescence emission was redshifted from 627 nm to 720 nm. To reduce cytotoxicity of Cu:CdS QDs, carboxymethyl chitosan (CMCS) molecules were selected to be grafting onto the surface of Cu:CdS QDs through amide bonds and the CMCS modification would greatly impede the release of cadmium ions . Both in vitro cellular cytotoxicity and hemolysis assay demonstrated that the CMCS/Cu:CdS QDs were highly biocompatible and the CMCS/Cu:CdS QDs as fluorescent probes were successfully applied in vivo imaging of small animals and this QDs can be easily metabolized by mice over time without adverse reactions . This new nanoprobes open up exciting opportunities for future biomedical applications .