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Uptake and Toxicity of Polystyrene NPs in Three Human Cell Lines
Summary
Researchers tested three sizes of polystyrene nanoparticles on human gut and liver cell lines and found that smaller particles (30 nm) were more toxic than larger ones (100 nm). Despite significant uptake by all cell types, the overall toxicity was low at tested concentrations. Interestingly, the nanoparticles entered cells mainly through a scavenger receptor pathway rather than the commonly assumed routes, which could change how scientists predict nanoplastic behavior in the human body.
Internalization of nanoparticles (NPs), including nanoplastic, is one of the key factors determining their toxicity. In this work, we studied the toxicity and mechanisms of the uptake of model fluorescent polystyrene NPs (PS NPs) of three different sizes (30, 50, and 100 nm) in three human cancer cells lines; two originated from gut tissue (HT-29 and Caco-2) and one originated from liver tissue (Hep G2). Toxicity was measured by Neutral Red Assay (NRU), whereas mechanisms of uptake were studied using flow cytometry and different uptake inhibitors. The toxicity of the studied NPs followed a general rule observed for NPs-the smaller ones were more toxic than the larger ones. This relationship was dose dependent; however, the overall toxicity of the studied NPs was very low, despite the significant uptake of PS NPs. Although clathrin- and caveolin-dependent uptake is generally accepted as a major route of NP uptake, the inhibition of both mechanisms did not affect PS NP uptake in the cell lines studied in this work. Further experiments revealed that the major route of PS NP uptake in these cells is a scavenger receptor-mediated uptake.