A new approach to studying the effects of ionising radiation on single cells using FTIR synchrotron microspectroscopy

• Prostate cancer cells derived from brain metastasis (DU-145 cell line) were used as a model.
• Single cells were irradiated with a controlled number (20–4000) of 1 MeV protons from the Cracow microbe.
• After fixation, irradiated and control cells were investigated using FTIR microspectroscopy.
• Quantitative and qualitative changes in phosphodiester region associated with DNA radiation damage, were observed.

The effect of ionizing radiation on single cells using a proton source was investigated using Fourier transform infrared (FTIR) microspectroscopy. The prostate cancer cells (DU-145) were irradiated by a specific number (50, 200, 400, 2000 and 4000) of protons per cell. Next after fixing the cells with 70% ethanol micro-FTIR spectra were obtained using both: (a) the synchrotron radiation source with a Mercury–Cadmium–Telluride (MCT) detector and (b) a globar source with a focal plane array (FPA) detector. FTIR spectra obtained from both instrumental configurations were analyzed independently to investigate the changes in the DNA phosphodiester region (1150–950 cm−1) of irradiated and control (untreated by ionizing radiation) cells.A Principal Component Analysis (PCA) scores plot revealed distinct clusters for all groups of irradiated cells, even for those irradiated by the smallest dose of protons. The dose-dependent changes in the relative intensities of DNA peak at 970 cm−1 (ribose-phosphate skeletal motions), along with a shift of the O–P–O band corresponding to the symmetric phosphodiester stretching mode at 1090 cm−1 were observed. The results demonstrate that FTIR spectroscopy is a promising tool to investigate DNA damage in single cells and may become an important tool in assessing cell damage following radiotherapy.