الفهرس 
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Abstract
Great efforts are currently devoted to fabricate high-quality quantum dots (QDs) in aqueous solutions with high biocompatibility and reduced cytotoxicity for biomedical applications. Two QDs 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 photo irradiation 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 the first excitonic absorption and emission peaks without photobleaching compared with CdSe~GSH system. X-ray diffraction showed that there is no change in the crystalline phase structure of the CdSe/ZnS~GSH system after 1 hr irradiation. Cell viability assessment in the dark demonstrated that no cytotoxic effects were shown upon incubation of both CdSe~GSH and CdSe/ZnS~GSH QDs with normal human skin cell line (HFB-4) or human breast adenocarcinoma cell line (MCF-7) for incubation periods up to 72 hrs and at concentration up to 400 nM. Under irradiation conditions using low laser power for different exposure times, CdSe/ZnS~GSH showed more stability and less cytotoxicity than CdSe~GSH at longer exposure time and also after 2 hrs post-exposure. The present study demonstrates that CdSe/ZnS~GSH system following low intensity photoexcitation exhibits high Photostability, high biocompatibility and reduced cytotoxicity with a relatively high PL efficiency in aqueous medium. This makes this system attractive for several important biomedical applications.