Effects of morphology and surface hydroxyl on the toxicity of BiOCl in human HaCaT cells

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Recently, bismuth oxychloride nanomaterials (BiOCls) are showing great promise in pollutant removal. Residues from these environmental remediations are potential hazardous materials. Unfortunately, human health risks of BiOCls are still unexplored widely. In the present study, we focused on the influence of physicochemical properties on the cytotoxicity of BiOCls toward a human skin derived cell line (HaCaT). Results showed that morphology and surface hydroxyl both had a profound effect on the toxicity of BiOCls. Microsphere-shaped BiOCl caused less toxicity than nanosheet-shaped BiOCl because of weaker particle-membrane interactions, while the presence of surface hydroxyl on microsphere-shaped BiOCl significantly raised the toxicity owing to the increased interaction with cell membrane. Both microsphere-shaped BiOCl with surface hydroxyl and nanosheet-shaped BiOCl caused significant cell membrane damage (PI uptake and LDH release), however, based on the different mechanism. The former may be a predominant “chemical” mechanism involved an oxidative stress paradigm, as manifested by elevated ROS and depleted GSH, while the latter is mainly due to a direct “physical” damage to cell membrane. Both “physical” and “chemical” response led to cell death. Furthermore, a set of experiments including MMP collapse, cell cycle arrest, and apoptosis/necrosis were conducted to propose a scenario for toxicological aspects of BiOCls. Data presented here would help to enable the rational design of BiOCls for either reducing their unintended consequences or increasing their application potentials.