X-ray radiation-induced effects in human mammary epithelial cells investigated by Raman microspectroscopy

Micro-Raman technique can be particularly useful to investigate the chemical changes induced in structure, protein, nucleic acid, lipid, and carbohydrate contents of cells. The aim of this work is to inspect the possibility to employ Raman microspectroscopy to detect biochemical modifications in human mammary epithelial cells after exposure to different Xray doses. The samples consisted of cells cultured on polylysine-coated glass coverslips. After the exposition, control and treated cells were washed in phosphate-buffered saline (PBS) and then fixed in paraformaldehyde 3.7%. They were examined using a confocal micro-Raman system equipped with a He-Ne laser (?? = 632.8 nm; power on the sample= 3.5mW). Differences in the intensity ratio of specific Raman vibrational markers commonly assigned to phenylalanine and tyrosine amino acids (at 1000, 1030, 1618 cm-1), DNA bases (787, 1090, 1305 cm -1), and amide III (1237, and 1265 cm -1) with respect a reference peak (the one of lipids at 1450 cm-1) were evidenced between control and exposed cells. These differences may be indicative of damage in exposed cells as the fragmentation of individual amino acids and DNA bases, crosslink effects in molecular structure of DNA and protein conformational change that especially tend to "unwind" the protein due to the breaking of hydrogen bonds between peptide chains