The phenomenon of positronium formation in biological material brings new possibilities formedical diagnostics. This thesis presents a method for determining mean positronium lifetme in microvesicles isolated from the culture of beta-pancreatic cells using low-vacuum filtration technique combined with the ultracentrifugation. The concentration of microvesicles in the prepared samples was tested with qNano particle analyzer, the operation of which is based on the TRPS (Tunable Resistive Pulse Sensing) technology. Before starting the actual measurements, Positron Annihilation Lifetime Spectrometer was adjusted accordingly, e.g. by equipping it with a thermostat which allows to precisely control the temperature in the system. A series of measurements was performed to check the temperature stability and a calibration curve was obtained, on the basis of which it is possible to accurately determine the temperature of the sample during the measurement. The positron source was additionally secured against leakage, which may occur when testing with liquid samples. Parafilm was used for this purpose, the positronium lifetime in it changes with temperature, what was taken into account in data analysis. The positronium lifetime in microvesicles cultured under normoglycemic and hyperglycemic conditions was investigated. The values were 1.80 ns and 1.77 ns respectively, thus not significantly different from the lifetime determined in the PBS buffer in which microvesicles were suspended (g = 1.80 ns). On the basis of the obtained results, it can be concluded that to conduct research with microvesicles using the presented method, it is necessary that the samples have a higher concentration of vesicles.
The development of a method for determining ortho-Positronium lifetime in extracellular vesicles using Positron Annihilation Lifetime Spectroscopy