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The effects of concentration, duration of exposure, size and surface function of polymethyl methacrylate micro/nanoplastics on human liver cells
Summary
Researchers tested the effects of polymethyl methacrylate micro- and nanoplastics on human liver cells, varying the particle concentration, exposure duration, size, and surface chemistry. They found that smaller particles and those with specific surface modifications caused greater cellular damage, including reduced viability and increased oxidative stress. The study suggests that the physical and chemical properties of microplastics play a critical role in determining their potential toxicity to human tissues.
Micro/nanoplastics (MP/NP) are pervasive contaminants that are detected throughout the environment in diverse matrices. Exposure to MP/NP have been demonstrated in humans by their presence in numerous body fluids and tissues. Due to the large quantity of production and broad applications, polymethyl methacrylate (PMMA) MP/NP have frequently been measured in surveys of microplastics in the environment. The effects of size, surface charge (aminated, carboxylated or non-functionalized), concentration, and exposure duration of PMMA particles in HepG2 human liver cells were evaluated in this study. The majority of PMMA MP/NP were non-cytotoxic. Some sporadic cytotoxicity was measured but it did not follow discernable trends. Confocal images revealed that 50, 100, and 1000 nm PMMA MP/NP were all taken up by HepG2 cells irrespective of surface charge. Particle size significantly affected caspase-3 release (p = 0.0002). Apoptosis was induced in only a small number of cells at 24 and 48 h for 50 nm and 1000 nm MP/NP. From 72 - 120 h, apoptosis increased in a time dependent manner for 50 nm beads at 100 µg/mL for all three surface functionalizations, with amine beads having the highest apoptosis at 120 h (36 %). Production of the pro-inflammatory interleukin-8 (IL-8) increased > 2x when the duration of exposure increased from 4 to 24 h irrespective of particle size, charge, or concentration. Collectively, PMMA MP/NP were not cytotoxic at the concentrations tested, but were able to translocate into HepG2 cells, release caspase-3, induce apoptosis, and produce IL-8 in a time dependent fashion.