Analyses of ionizing radiation effects in vitro in peripheral blood lymphocytes with Raman spectroscopy

The use of Raman spectroscopy to measure the biochemical profile of healthy and diseased cells and tissues may be a potential solution to many diagnostic problems in the clinic. Although extensively used to identify changes in the biochemical profiles of cancerous cells and tissue, Raman spectroscopy has been used less often for analyzing changes to the cellular environment by external factors such as ionizing radiation. In tandem with this, the biological impact of low doses of ionizing radiation remains poorly understood. Extensive studies have been performed on the radiobiological effects associated with radiation doses above 0.1 Gy, and are well characterized, but recent studies on low-dose radiation exposure have revealed complex and highly variable responses. We report here the novel finding that demonstrate the capability of Raman spectroscopy to detect radiation-induced damage responses in isolated lymphocytes irradiated with doses of 0.05 and 0.5 Gy. Lymphocytes were isolated from peripheral blood in a cohort of volunteers, cultured ex vivo and then irradiated. Within 1 h after irradiation spectral effects were observed with Raman microspectroscopy and principal component analysis and linear discriminant analysis at both doses relative to the sham-irradiated control (0 Gy). Cellular DNA damage was confirmed using parallel γ-H2AX fluorescence measurements on the extracted lymphocytes per donor and per dose. DNA damage measurements exhibited interindividual variability among both donors and dose, which matched that seen in the spectral variability in the lymphocyte cohort. Further evidence of links between spectral features and DNA damage was also observed, which may potentially allow noninvasive insight into the DNA remodeling that occurs after exposure to ionizing radiation.