Detection of DNA Damage in Nucleoids Irradiated with Protons at Different Dose Rates Using the Comet Assay

Abstract

In vivo, DNA undergoes continuous repair, which masks the level of DNA damage induced by ionizing radiation. To overcome this limitation, this study irradiated mouse splenocyte nucleoids, where DNA repair is already inactive. Nucleoids are DNA-protein complexes formed by cell lysis and the removal of membranes and some nuclear proteins. An alkaline version of the Comet assay was used to assess the level of DNA damage in nucleoids. Nucleoids were embedded in agarose on glass slides, which were then irradiated with protons or X-rays. In the dose range of 3–13 Gy, %TDNA of nucleoids (the percentage of DNA in the comet tail) irradiated with protons in Flash (dose rate ~100 Gy/s), single-pulse Flash–Splash (~10⁶ Gy/s), and Conv modes (<1 Gy/s) exhibit a dose-dependent pattern and are comparable to those observed with X‑ray irradiation in Conv mode. The obtained data indicate the possibility of using such nucleoids for biodosimetry using the Comet assay with varying dose rates.