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Enhanced Macrophage Internalization of Photoaged Nanoplastics Mediated by Altered Serum Albumin Secondary Structure
Summary
Researchers found that nanoplastics exposed to sunlight in water undergo surface changes that alter how they interact with blood proteins, specifically human serum albumin. The aged nanoplastics caused the protein to unfold and change its structure, which in turn made immune cells take up the plastic particles more readily. The study suggests that environmental aging of nanoplastics could increase their biological activity and potential health effects once they enter the body.
After nanoplastics (NPs) experience photoaging in an aquatic environment, they may enter blood circulation of organisms and interact with proteins, which significantly affect their cellular uptake and biological effects. In this study, polystyrene nanoplastics (PSNPs) and human serum albumin (HSA) were chosen as representative models of NPs and proteins, respectively. The photoaged PSNPs exhibited decreased particle size and increased surface oxidation, which not only promoted their binding with HSA but also led to preferential binding with the α-helix regions of HSA. Consequently, the α-helical content of the adsorbed HSA molecules on photoaged PSNPs decreased significantly, leading to a denaturation effect comparable to thermal treatment. Dissolved substances released from PSNPs had a negligible impact on HSA's conformation. The denatured HSA activated additional endocytic pathways, notably enhancing SR-A1-mediated endocytosis of mouse monocyte macrophages (RAW 264.7), which thus promoted the cellular uptake of the photoaged PSNPs compared with pristine ones. This study suggests that photoaging may greatly alter the interactions of NPs with proteins, thereby influencing cellular uptake mechanisms, and then alter their potential biodistribution and biological effects in vivo.