Sci-Thurs AM: YIS-10: Raman Microscopy of Single Human Tumor Cells Irradiated in Vitro : A New Prospect for Experimental Radiobiology

Abstract

Continued investigation into radiation interactions with cells and tissues is necessary to shed light on outstanding radiobiological issues such as the variation in patient radiosensitivity, the inability to monitor a patient's radioresponse during the course of an extended treatment, and the failure of current models to predict cell survival or tumor control at single high doses. One technique that shows promise for radiobiological studies is Raman microscopy (RM). RM involves focusing an optical wavelength laser through a high power microscope objective onto a sample, inducing molecular vibrations and creating inelastically scattered photons with frequencies and intensities characteristic to the properties of the molecules in the sample. The resulting Raman spectrum collected provides a detailed description of the molecular composition within the sampling volume. In this study, human prostate tumor cells are cultured in vitro and exposed to single high doses (15–50 Gy) of 6 MV radiation. Irradiated and unirradiated cell cultures are re-incubated for varying amounts of time post-exposure, up to five days. Principal component analysis (PCA) is used to show that the Raman spectra collected from irradiated cells display a novel radiobiological effect that is correlated with both dose and post-exposure incubation time. The measurable effect is expressed as varying concentrations of lipids, nucleic acids, and conformational protein structures within irradiated cells as compared to unirradiated cells. PCA is shown to be useful in distinguishing the radiation-induced changes in cell spectra from the natural spectral variability within a cell culture due to cell cycle and other growth conditions.