The potential of Raman spectroscopy for the molecular characterisation of human tumours

In this study Raman spectroscopy was employed distinguish between normal and abnormal human tissue. Raman spectra were obtained using a confocal Raman microspectrometer and a laser excitation of 514.532nm for a number of healthy tissues (Tonsil and Cervix) as well as for their diseased counterparts. Each tissue type was classified and its various spectral components were associated with vibrations, rotations etc. of the chemical bonds in the tissues' constituent components. Raman bands have been attributed to biological compounds such as proteins, lipids and DNA as well as to chemical bonds within these compounds such as, C=O stretch in Amide I (1645-1680 cm^-1), NH bending in Amide III (1230-1310 cm^-1), phenyl ring in Phenylalanine (1004 cm^-1). Changes in the relative intensities, position, and width of these bands relate to the composition of the sample. Differences between healthy and diseased tissue with progression to malignancy have been identified and include; an increase in intensity of the phenylalanine ring breathing band (1004 cm^-1), the C-C stretch of proteins (1082 cm ^-1), Amide I band (1655 cm^-1) and the C-N stretching modes of proteins (1082cm^-1). Decreases in relative intensities were also observed, and include a decrease in intensity of the CH₂ deformation (1295 cm^-1), CH₂ bending of proteins and lipids (1445 cm^-1), and the C=O stretching of proteins (1695 cm ^-1). The molecular origin of the observed spectral changes is discussed.