Raman microspectroscopy investigation of X-ray radiation induced effects in human mammary epithelias cells

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. Micro-Raman technique can be particularly useful in investigating the chemical changes induced in protein, nucleic acid, lipid, and carbohydrate contents of cells. In the present study we exposed human mammary epithelial cells to X-ray (up to 10 Gy) and subsequently fixed in paraformaldehyde. Samples were examined using a micro-Raman spectrometer equipped with a confocal microscope (Horiba-Jobin Yvon), a He-Ne laser and a CCD detector with a chip size of 1024x256 equipped with a Peltier cell with a grating of 600 grooves/mm. An automatic numerical data treatment based on wavelet algorithm was used in order to suppress the noncorrelated signal, to subtract the background signal and to increase the quantitative readibility of the Raman signal. Data were then analyzed by using Principal Component Analysis. The software employed in this work was properly written for Raman cells analysis purposes and is based on the toolbox 3.5 for MATLAB, from Eigenvector Research. The differences observed in the peak of the aromatic amino acids, amide I, amide III and nucleic acids may be indicative of damage in irradiated cells such as the fragmentation of individual amino acids and DNA bases, crosslink effects in molecular structure of DNA and protein conformational changes because of the breakage of hydrogen bonds between peptide chains. Our preliminary analysis indicates a good sensitivity of the micro-Raman technique to detect the chemical changes induced by X-radiation on fixed biological samples at subcellular level. Therefore this technique could be used in the field of radiation therapy to monitor the minimal doses sufficient to inactivate cancer cells thus reducing the overall radiation dose and minimising damage to the surrounding healthy cells