To function properly cells need appropriate mechanical properties, which change drastically with various diseases or exposure to foreign substances such as TiO2 nanoparticles. We are often exposed to nanoparticles as they are omnipresent in the atmosphere, food, and other every-day products. Studies have shown that TiO2 nanoparticles are nontoxic when exposed to skin, but when exposed to our interior organs they can cause cell damage or necrosis. To better understand the danger and interaction mechanisms of TiO2 nanoparticles it is sensible to study changes in cell mechanics when the cells are exposed to TiO2 nanoparticles. In this MSc thesis, we have observed mechanical properties of lung epithelial cells when exposed to osmotic shock using STED and confocal microscopy. The used method is simple, quantitative, and provides insight to an initial passive response and to active adaptation of the cell to the new environment. First, we studied osmotic shock of healthy cells at different environmental osmolarities and compared the responses with Boyle-van't Hoff relation. Then we disrupted actin cytoskeleton with Latrunculin A and observed the cells' response to osmotic shock. We compared the osmotic shock of cells with chemically disrupted cytoskeleton with the response of cells incubated with TiO2 nanoparticles. Last, we observed the responses of cell incubated with different quantities of nanoparticles and at different incubation times. We have observed that lung epithelial cells respond to osmotic shock according to Boyle-van't Hoff relation. When repeating osmotic shock multiple times on the same cell we notice that the response changes after two or three repetitions. Actin depolymerization with Latrunculin A results in the inability of a cell to actively adapt to the new environment. Conversely, cells exposed to TiO2 nanoparticles have a smaller passive response to the osmotic shock, which also gets weaker with higher quantities of nanoparticles. We observed that the osmotic response gets restored with the longer incubation time of cells with TiO2 nanoparticles. More generally, this work is a contribution towards the understanding the role, safety, and the general effects of TiO2 nanoparticles in different bio-relevant environments and materials.
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