Alpha particles from inhaled radon progeny are the most important source of irradiation of the human respiratory tract. It is therefore pertinent to study the risk by investigating the biological effects of a small number of alpha particles crossing the cell nuclei. For such purposes, cells are seeded on a substrate foil and covered by the nutritive medium. However, the thickness of the nutritive medium layer cannot be controlled to the desired thickness each time. Thus, alpha-particle irradiation should be performed from the side of the substrate foil, i.e., the side not in contact with the cells. Therefore, the substrate used should be thin enough to allow alpha particles with nominal energy to pass through. In this way, the alpha particles can reach the living cells through the thin substrate foils, while the positions where the alpha particles hit the cells can also be determined from the positions of the etched alpha-particle tracks, the latter being essential for dosimetric determination. In the present study, we propose a non-sophisticated method to prepare thin CR-39 detectors from etching commercially available CR-39 SSNTDs in NaOH/Ethanol and the roughness had been studied using atomic force microscope (AFM). As an example for practical use, custom-made petri dishes, with holes drilled at the bottom and covered with thin CR-39 detectors, were used for culturing cells. On the other hand, another type of detector, namely, the commercially available colourless LR 115 SSNTDs, with a thickness of about 14 <m of cellulose nitrate as the active layer, are also investigated for the feasibility in acting as substrate foils to make custommade cell dishes for alpha-particle radiobiological experiments. In the second part of the thesis, biological methods such as the terminal dUTP transferase-mediated nick end-labeling (TUNEL) fluorescence method and neutral Comet assay would be applied by using the custom-made CR-39 cell dishes to study the effect of ionizing radiation on living cells. The TUNEL fluorescence method is used to detect apoptosis originally and is now used to detect strand breaks induced by ionizing radiation (i.e., alpha particles). A special method was developed to use the custom-made cell dishes to count the alpha-particle transversals on the cell nuclei in radiobiological experiments. The results showed that there were more DNA stand breaks for hits on the HeLa cell monolayer by alpha particles with residual energies corresponding to higher linear energy transfer (LET) for the same dose. Besides, the results are also affected by bystander effects, with which nonirradiated cells also show similar responses as those in irradiated cells, and other environmental factors. On the other hand, a method to use Comet assay with the custom-made CR-39 cell dishes to detect the DNA double strand breaks (dsbs) was also developed. Comet assay allowed the degree of DNA damage (dsbs) to be related to the number of alpha-particle transversals, which were observed as alpha-particle tracks beneath the images of the stained DNA, both being captured by the confocal microscope.