Characterization of Bone and Bone-Based Graft Materials Using FTIR Spectroscopy

Abstract

Despite its static appearance, bone is a very dynamic living tissue that undergoes constant remodelling throughout life. After blood, bone is the second most commonly transplanted tissue in human medicine, and thus a thorough characterization of this material is of crucial importance. For instance, although it has been accepted that the whole bone strength is related to the bone mineral density (BMD), changes in this parameter often do not correlate with the probability of fracture. To improve the mechanical performance of bone, other material properties related to bone quality, and not only quantity, have to be investigated. FTIR spectroscopy constitutes an excellent tool to characterize the bone matrix because its main components (carbonated hydroxyapatite and collagen) absorb infrared radiation at distinct, almost complementary, regions within the 500-4000 cm-1 range. This not only enables the study of the main contributions of each component separately, but also allows a further investigation of relevant parameters that mostly affect the structural and mechanical properties of bone, as well as its active metabolism. Furthermore, FTIR analysis, particularly when combined with microscopic technologies, enables the measurement of spatial variations in bone composition, allowing their correlation with micro-to-macro morpho- structural properties. In clinical studies, this allows the comparison between sound and diseased bone, and the analysis of therapeutic effects of drugs, among many other examples. On the other hand, FTIR spectroscopy is also commonly used to characterize bone grafts. Moreover, evidence that optimizing the osteointegration requires a fundamental knowledge of the material properties both of the bone graft and of the host bone tissue, has driven to extensive research on this subject, often supported by FTIR spectroscopy.