Cell surface modifications induced by titanium dioxide nanoparticles in A549 cells

Several studies have been performed to understand the influence of titanium dioxide nanoparticles (TiO2-NPs) on cell function; however the effects of nanoparticle exposure on the plasma membrane have not been addressed so far. Since this interaction may alter cell metabolism and integrity, it is of importance to understand the modifications of the cell membrane, in particular of epithelial cells, upon particle exposure. To address this question, we exposed human pulmonary epithelial cells (A549) to various concentrations of TiO2-NPs, previously characterized by analytical transmission electron microscope (TEM), and evaluated nanoparticle interaction and cell surface modifications by means of scanning electron microscope (SEM). TiO2-NPs appeared as compact, fairly large agglomerates, entering into the cell directly through holes or by inward membrane bending followed by NP sinking. SEM images also showed a network of lengthened microvilli surrounding TiO2-NPs, indicative of a possible endocytotic mechanism. More detailed studies will be necessary to understand which of the two uptake mechanisms is the predominant one.