| The ever-increasing development of nanotechnology will inevitably lead to heightened levels of engineered nanoparticles in the aquatic environment. Therefore, information of the environmental behavior and ecological risks of nanoparticles are in urgent need before fulfilling the potential of nanotechnology completely.The bioaccumulation kinetics of thioglycolic acid stabilized CdTe quantum dots (TGA-CdTe-QDs) in a freshwater alga Ochromonas danica was investigated comprehensively for the first time in the present study. A substantial increase of the photoluminescence (PL)-based concentration of TGA-CdTe-QDs in the cells detected by flow cytometry indicated the uptake of intact nanoparticles. TGA-CdTe-QD internalization was further ascertained by the uptake experiment with heat-killed and cold-treated cells. Later, macropinocytosis was circumstantiated to be responsible for TGA-CdTe-QD translocation with the help of various pharmaceutical inhibitors. Once entering the cells, TGA-CdTe-QDs were concentrated mainly in the vacuoles as visualized by confocal microscopy. A biokinetic model, previously for heavy metals and organic pollutants, was used to simulate the hyperbolic correlation between TGA-CdTe-QD accumulation and exposure time. As limited by their diffusion from the bulk medium to the cell surface, TGA-CdTe-QD uptake rate increased proportionally with their ambient concentration. Although the PL of intracellular TGA-CdTe-QDs decreased quickly, only a small fraction of these nanoparticles were dissolved and their expulsion out of the cells was also slow. Hence, PL quenching was mainly due to surface modification of TGA-CdTe-QDs by intracellular biomolecules. Despite the substantial accumulation of TGA-CdTe-QDs, they had no direct acute effects on O. danica. Overall, our research shed a new light on nanoparticle bioaccumulation study and further improved our understanding about their behavior, effects and fate in the natural environment. |
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