Type I Collagen is one of the most abundant proteins of the extracellular matrix of the most organs. During chronological aging or in diseases, type I collagen undergoes biochemical and structural changes which can impact biomechanical and physiological properties of organs. In this study, we have investigated the age-related changes in the molecular organization of type I collagen in rat tails tendon using polarized Raman spectroscopy. Our results show that Amide I, amide III as well as the bands related to proline and hydroxyproline are highly sensitive to polarization and age-related. On the other hand, 1453 and 1270 cm⁻¹ do not show any preferential orientation. Depolarization and anisotropic ratios were used to provide information about the changes in orientation of collagen fibers with aging. The anisotropy degree of Raman bands increase from adult to old collagen, indicating a higher collagen fibers alignment to the fascicle backbone axis in old tendons, and consequently a higher straightness of collagen fibers. These data were correlated to those obtained using polarized second harmonic generation technique. Polarized Raman mapping showed a more homogeneous spatial distribution of collagen fibers alignment to the fascicle axis in old tendon. This confirms a higher straightness of collagen fiber with aging.

Principal components analysis (PCA) combined to Fourier transform infrared (FTIR) microspectroscopic imaging was used to screen biochemical changes associated to C6 glioma tumor from 7 to 19 days growth. Normal brain and tumor obtained at 7, 12, 19 days after C6 cell injection were used to develop a diagnostic model of brain glioma based on PCA analysis. This classification model was validated using extra-measurements on normal and tumor at 9 and 15 days post-implantation. The spatial and biochemical information obtained from FTIR/PCA maps can be used to improve the discrimination between normal and grading human glioma. The first 4 PCs which account for more than 93.6% of total spectral variance were used to construct pseudo-color scores maps and compared each map to the corresponding hematoxylin and eosin (H&E) staining. Our results reported that by correlating pseudocolor map scores with H&E staining it was possible to screen histological changes associated with tissue transformation. In fact, PC1 and PC4 were associated to the tumor, surrounding tumor and necrosis. Indeed, at day 7 after tumor implantation, FTIR investigations displayed a very small abnormal zone associated with the proliferation of C6 cells in the caudate putamen (CP). PC2 and PC3 described normal brain structures such as white matter (corpus callosum (CC) and commissura anterior (CA)) and some cortex layers (grey matter). After delipidation of the tissues, we were still able to differentiate between different tissue features based on nucleic acid and protein content. By comparing the patterns of the PC loads with the spectra of lipids extracted from white and gray matters, and DNA, we have identified some biochemical changes associated with tissue transformation. This work demonstrated that our classification model provides a successful histological classification of different brain structures.