Genotoxicity assessment of nylon and polyethylene microparticles in Caco‑2 cells

Microplastics (size 0.1µm - 5 mm) are ubiquitous in the environment, but their consequences on human health are still largely unknown. Nylon and polyethylene (PE) are widely used polymers in various applications, and although human exposure to them has been detected, the potential health effects are understudied. The aim of our study was to determine whether nylon microparticles induce toxicity in human colorectal adenocarcinoma Caco-2 cells and analyze the genotoxic potential of nylon and PE microparticles in these cells. The cells were exposed to 0.01-0.5 mg/ml of nylon (polyamide6) for 48 h, after which cell viability and cytotoxicity were analyzed with MTT and lactate dehydrogenase (LDH) assays, respectively. Reactive oxygen species (ROS) production was measured with dichlorofluorescein diacetate assay, as well as cytoplasmic and mitochondrial production of superoxide were analyzed with dihydroethidium (DHE) and MitoSOX assays, respectively. In addition, genotoxicity of both nylon (0.005-0.1 mg/ml) and PE (0.25-1 mg/ml) were analyzed with alkaline comet assay and micronucleus assay. Nylon microparticles decreased the viability of Caco-2 cells dose-dependently, yet no cytotoxicity was observed with LDH assay. In addition, the nylon microparticles induced the production of ROS as well as mitochondrial and cytosolic superoxide dose-dependently in Caco-2 cells. However, genotoxicity was not observed with either of the polymers. In conclusion, our study shows that high concentrations of nylon microparticles decreased cell viability and increased oxidative stress response in intestinal cells, with mitochondria being one possible target of toxicity while genotoxic effects were absent. Furthermore, when compared to our previous studies, nylon microparticles were more toxic to Caco-2 cells than PE particles. This study brings important information about the toxicity of microplastic particles in human Caco-2 cells providing valuable data for risk assessment.