The irradiation system consisting of an α-source and disc holder has been developed in the Heavy Ion Laboratory, University of Warsaw. A simple exposure system for irradiation of biological samples consists of the Am-241 disc source, source holder and biological samples cultured in special Petri dishes. The irradiation system has been investigated to determine the alpha spectrum and dose distribution in irradiated single cell layer attached to the Mylar foil. Commercial Am-241 disc source of 50 mm in diameter, with a radioactive element embedded into a substrate layer was examined to established the uniformity of surface radioactivity over the disc source. The experimental device is equipped with cell dishes of 40 mm in diameter and a 6 µm thick Mylar foil bottom. Care was taken for homogenous irradiation of the cells. Dose calibration for the irradiation system was calculated taking into account source-to-target geometry.

Exosomes are spherical membrane nanovesicles secreted from cells, and they play an important role in tumor immune response, metastasis, angiogenesis, and survival. Studies investigating exosomes isolated from cells exposed to photon radiation commonly used in conventional radiotherapy demonstrate the influence of this type of radiation on exosome characteristics and secretion. There is currently no research investigating the effects of densely ionizing particles such as protons and alpha radiation on exosomes. Thus we have evaluated the cellular response of human prostate cancer cells exposed to 0, 2, and 6 Gy of alpha radiation emitted from the Am-241 source. Irradiated PC3 and DU145 cell lines, characterized by differences in radiosensitivity, were studied using apoptosis, LDH, and IL-6 assays. Additionally, the corresponding concentration and size of isolated exosomes were measured using NTA. We found that exposure to ionizing radiation resulted in gross changes in viability and cell damage. There were increased amounts of apoptotic or necrotic cells as a function of radiation dose. We demonstrated that irradiated PC3 cells secrete higher quantities of exosomes compared to DU145 cells. Additionally, we also found no statistical difference in exosome size for control and irradiated cells.

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