Nanoparticles are particles that measure ≤ 100 nm in at least one dimension. Because of their size, nanoparticles possess unique properties and are widely applied in many different industries. These unique properties of nanoparticles also reflect in their ability to inflict changes on a cellular level, which represents a potential health risk and is the subject of extensive ongoing research. Exposure to certain nanoparticles is linked to inflammatory response within many organs or organic systems, with a proven link between inhalation of nanoparticles and chronic inflammatory respiratory diseases. Exposure to inhaled nanoparticles is supposedly further linked to the development of cardiovascular diseases such as atherosclerosis. Atherosclerosis is a complex, multifactorial chronic inflammatory disease with no clearly defined risk factors or causes. Recent studies highlight the activation of vascular endothelial cells and adhesion of leukocytes as key initiating events in the development of atherosclerosis. To examine the relationship between nanoparticle exposure and the development of atherosclerosis, we chose to develop a method to measure the adhesion time of monocytes to the vascular endothelium using optical tweezers. Our results indicate that exposure of endothelial cells to TiO2 nanotubes (TiO2NT) in vitro shortens the adhesion time of monocytes, which could result from the potentially toxic effects of TiO2NT and consequential activation of endothelial cells. The effect of TiO2NT was comparable to the one of thrombin, which we chose as a positive control to activate endothelial cells. With the application of suggested improvements, the developed method could be redesigned into a standard in vitro method to assess attachment of monocytes to endothelium. Furthermore, our preliminary results from confocal fluorescent microscopy of adhesion molecules indicate a correlation between the distribution of adhesion molecules on endothelial cells and monocyte adhesion times. We propose a high-throughput working model, using confocal fluorescent microscopy of adhesion molecules, which would enable one to analyze the effect of nanomaterials and chemicals on the development of atherosclerosis in a time-efficient and affordable manner.
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