Interactions between vascular endothelial cells and nanoparticles investigated by single-cell mechanics

Abstract : Inhalation of airborne nanoparticles (NPs) has been correlated with cardiopulmonary disease. To better understand the underlying mechanisms, human aortic endothelial cells (HAECs) were exposed in vitro to zinc oxide (ZnO) and silicon dioxide (SiO2) NPs at various doses. By using atomic force microscopy based single-cell compression, we observed that ZnO NPs at 10 µg/ml produced stiffening of the cellular membrane and cytoskeleton. At higher ZnO NP doses, cell volume increased by up to 280%. SiO2 NPs had a similar but milder effect. A simple balloon model based on Hertzian mechanics yielded a membrane Young's modulus (Em) increase from 5.0 ± 2.1 MPa to 7.7 ± 1.8 MPa for ZnO NPs and to only 5.49 ± 0.75 MPa for SiO2 NPs. The results can be rationalized by unregulated ion influx leading to increased intracellular osmotic pressure. Single-cell mechanics provides sensitive and quantitative measurements that yield insight into NP - cell interactions.