Rotational Motion Amplifies Oxidative Responses to Polystyrene Nanoplastics: An In Vitro Proof-of-Concept and Particle-Impact Model.

Micro- and nanoplastics have been detected in human blood and arterial plaques, but how particle motion modifies cellular responses remains unclear. Here, we used a simple rotational exposure system as an in vitro proof-of-concept to test 80 nm polystyrene (PS) nanoplastics in A549 cells. Exposure to 100 μg/L PS nanoplastics or rotation at 6.7 rpm alone produced no detectable change in tetramethylrhodamine ethyl ester (TMRE) fluorescence or intracellular reactive oxygen species (ROS) under the conditions tested. In contrast, the combined treatment increased TMRE fluorescence and induced a pronounced ROS response without altering the mitochondrial-to-nuclear DNA ratio. Separately, an idealized particle-impact model predicted that single-particle impact force increases strongly with particle size and flow velocity at arterial bifurcations. Because the rotation speed was not calibrated to physiological wall shear stress, and A549 cells are not endothelial cells, these findings do not establish vascular toxicity. Rather, they show that particle motion can modify cellular responses to PS nanoplastics in vitro and support further testing in calibrated endothelial flow systems.