Photoluminescence and photostability investigations of biocompatible semiconductor nanocrystals coated with glutathione using low laser power

Great efforts are currently devoted to fabricate high-quality quantum dots (QDs) in aqueous solutions for biomedical applications. Two biocompatible systems consisting of core (CdSe) and core/shell (CdSe/ZnS) QDs surface modified with glutathione (GSH), named CdSe-GSH and CdSe/ZnS-GSH, respectively, were built. Upon photoirradiation using low laser power, both systems in HEPES buffer (pH 7.2) showed significant photoluminescence (PL) enhancements. CdSe/ZnS-GSH showed much less blue shifts in excitonic absorption and emission peaks without photobleaching compared with CdSe-GSH QDs system. X-ray diffraction showed that there is no change in the crystalline phase structure of the CdSe/ZnS-GSH QDs system after 1 h irradiation. Cell viability assessment, in the dark, demonstrated that no cytotoxic effects were shown upon incubation CdSe/ZnS-GSH QDs with normal human skin cell line for periods up to 72 h and at concentrations up to 100 nM. The present study demonstrates that CdSe/ZnS-GSH QDs system exhibits a high photostability with a relatively high PL efficiency in aqueous medium following low intensity photoexcitation, without dark cytotoxicity, making this system attractive for several important biomedical applications.