Raman spectroscopy of osteoporotic rat tibia

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Kontoyannis, Christos
Orkoula, Malvina
Vradaki, Martha

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Fractures are the most frequent health problem associated with bone. Metabolic diseases, such as osteoporosis, affect skeletal integrity, reduce strength and toughness of bone and lead to increased risk of fragility. In the present work, changes in the amount and/or quality of bone were studied in osteoporotic tibiae from female wistar rats compared to healthy controls. Osteoporosis was induced through ovariectomy. Bone composition and quality was evaluated employing Raman Spectroscopy. Several spectra were recorded. The height of the primary phosphate band (PO43-, v1) for the mineral at 959 cm-1, the carbonate peak at 1070 cm-1 under the combined phosphate-carbonate envelope 1010-1100 cm-1 spectral range, the matrix bands at 855 cm-1 (hydroxyproline), 875 cm-1 and 920 cm-1 (proline), as well as the three major peaks under amide I envelope (1620-1710 cm-1) were measured after proper baselinining and deconvolution. The mineral to matrix ratio [959 cm-1 / (855 cm-1 + 875 cm-1 + 920 cm-1)] was reduced, suggesting decreased mineral quantity in the osteoporotic tibiae compared to controls. Carbonate levels remained stable which implies absence of new bone tissue formation, though bone is known to follow a constant renewal procedure. The mineral to amide I envelope ratio exhibited an increasing trend suggesting that amide I cannot be used as collagen metrics as it is subject to polarization effects. Further analysis of the amide I envelope shows that the band changes shape following bone disease, which is a result of the change in the ratio of the peaks lying under the amide I envelope. Therefore, changes in collagen cross-linking accompany reduction of mineral amount and lead to reduced strength and increased fragility in osteoporosis.



Raman, Osteoporosis, Tibia, Collagen, Apatite