The present study examines the stability and cytotoxicity of two quantum dots (QDs) systems in cell culture medium in the presence and absence of a thin layer of a ZnS shell. The two systems were built from a core, CdSe, and surface modified with glutathione (GSH), named CdSe∼GSH and CdSe/ZnS∼GSH. CdSe/ZnS∼GSH QDs exhibited a high photostability with a pronounced enhancement in photoluminescence in cell culture medium. Both systems showed insignificant reduction in cell viability of HFB-4 and MCF-7 cell lines in the dark. Following 60 min of low laser power exposure (irradiance of 10 mW cm−2), CdSe∼GSH QDs showed a remarkable decrease in cell viability, which may result from the detachment of GSH molecules, whereas CdSe/ZnS∼GSH QDs showed an insignificant decrease either immediately after irradiation or even 2 h post-exposure, which can be attributed to the high affinity between ZnS and GSH coatings. This study demonstrated that a thin layer of ZnS shell played a crucial role in the stability of CdSe/ZnS∼GSH QDs in cell culture medium with an improvement in luminescence efficiency, whereas surface modification with GSH molecules in the presence of ZnS showed no significant cytotoxic effects before or after photoirradiation, which makes this system attractive for several biomedical applications.
Biomedical applications of quantum dots (QDs) have become a subject of a considerable concern in the past few
decades. The present study examines the stability and cytotoxicity of two QDs systems in cell culture medium in the
presence and absence of a thin layer of ZnS shell. The two systems were built from core, CdSe QDs, surface modified
with glutathione (GSH), named CdSe∼GSH and CdSe/ZnS∼GSH. Our results demonstrated that 0.7 nm layer of ZnS
shell played a significant role in the stability of CdSe/ZnS~GSH QDs in supplemented cell culture medium (RPMI).
Also, a significant improvement in the physicochemical properties of the core CdSe QDs was shown by maintaining
their spectroscopic characteristics in RPMI medium due to the wide band gap of ZnS shell. Both systems showed
insignificant reduction in cell viability of HFB-4 or MCF-7 cell lines in the dark which was attributed to the effective
GSH coating. Following photoirradiation with low laser power (irradiance 10 mW cm-2), CdSe~GSH QDs showed a
significant decrease in cell viability after 60 min irradiation which may result from detachment of GSH molecules. Under
the same irradiation condition, CdSe/ZnS~GSH QDs showed insignificant decrease in cell viability or after 2 h
incubation from laser irradiation which was attributed to the strong binding between ZnS and GSH coatings. It can be
concluded that the stability of CdSe core QDs was significantly improved in cell culture medium by encapsulation with a
thin layer of ZnS shell whereas their cytotoxicity and photo-cytotoxicity are highly dependent on surface modification.
As nanotechnology continues to develop, an assessment of nanoparticles’ toxicity becomes very crucial for biomedical applications. The current study examines the deleterious effects of pre-irradiated gold nanoparticles (GNPs) solutions on primary rat kidney cells (PRKCs). Spectroscopic and transmission electron microscopic studies demonstrated that exposure of 15 nm GNPs in size to pulsed laser caused a reduction both in optical density and mean particle diameter. GNPs showed an aggregation when added to the cell culture medium (DMEM). This aggregation was markedly decreased upon adding serum to the medium. Under our experimental conditions, trypan blue and MTT assays revealed no significant changes in cell viability when PRKCs were incubated with non-irradiated GNPs over a period of 72 h and up to 4 nM GNPs concentration. On the contrary, when cells were incubated with irradiated GNPs a significant reduction in PRKCs viability was revealed.
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