Cytotoxicity of the soluble and insoluble fractions of atmospheric fine particulate matter.

Inhaled atmospheric fine particulate matter (PM2.5) includes soluble and insoluble fractions, and each fraction can interact with cells and cause adverse effects. PM2.5 samples were collected in Jinan, China, and the soluble and insoluble fractions were separated. According to physiochemical characterization, the soluble fraction mainly contains water-soluble ions and organic acids, and the insoluble fraction mainly contains kaolinite, calcium carbonate and some organic carbon. The interaction between PM2.5 and model cell membranes was examined with a quartz crystal microbalance with dissipation (QCM-D) to quantify PM2.5 attachment on membranes and membrane disruption. The cytotoxicity of the total PM2.5 and the soluble and insoluble fractions, was investigated. Negatively charged PM2.5 can adhere to the positively charged membranes and disrupt them. PM2.5 also adheres to negatively charged membranes but does not cause membrane rupture. Therefore, electrostatic repulsion does not prevent PM2.5 attachment, but electrostatic attraction induces remarkable membrane rupture. The human lung epithelial cell line A549 was used for cytotoxicity assessment. The detected membrane leakage, cellular swelling and blebbing indicated a cell necrosis process. Moreover, the insoluble PM2.5 fraction caused a higher cell mortality and more serious cell membrane damage than the soluble fraction. The levels of reactive oxygen species (ROS) enhanced by the two fractions were not significantly different. The findings provide more information to better understand the mechanism of PM2.5 cytotoxicity and the effect of PM2.5 solubility on cytotoxicity.