The intermolecular cross-linking of bone collagen is intimately related to the way collagen molecules are arranged in a fibril, determines certain mechanical properties, and has been suggested to be involved in the mineralisation initiation process. Once type I collagen has been synthesised by osteoblasts, it undergoes extensive posttranslational modifications, resulting in a characteristic pattern of cross-links. The post-translational modifications of the organic matrix are important for both its structural and mechanical properties, and disruption of the cross-linking can result in dysfunction of the tissue. Raman microspectroscopy allows the analysis of minimally processed bone blocks and provides simultaneous information on both the mineral and organic matrix (mainly type I collagen) components with a spatial resolution of ~1 μm. The purpose of the present study was to validate Raman spectroscopic parameters describing one of the major mineralising type I trivalent cross-links, namely pyridinoline (PYD). To achieve this, a series of collagen cross-linked peptides with known PYD content (as determined by HPLC analysis), porcine skin, and porcine predentin and dentin were analysed by Raman microspectroscopy. Spectra were further processed by means of difference and second derivative spectral resolution methods. The results of the present study confirm that it is feasible to monitor PYD trivalent collagen cross-links by Raman spectroscopic analysis in mineralized tissues, through a spectral components ~1660 wavenumbers exclusively. This allows the determination of the relative pyridinoline content in undecalcified bone tissues with a spatial resolution of ~1 μm, thus enabling the correlation with histologic and histomorphometric parameters.
Disclosure: The authors declared no competing interests.