Chemical microstructure of cortical bone probed by Raman transects

Raman transects, microspectra taken at equal intervals along a line, are us ed to explore the microstructure of human cortical bone. Transects of 50 sp ectra taken at 2.5 mu m intervals across an osteon show spatial differences in local mineral and protein composition as different physiological struct ures are traversed. Differences in mineral composition are seen near the ri m of an osteon and further out in the lamellae. The blood vessel wall, prim arily composed of collagen and elastin, is detected inside the Haversian ca nal. Factor analysis is used to explore the data set and reveals difference s in mineral composition. Factor analysis also yields one bone matrix compo nent, an osteoidal tissue component, and one blood vessel protein component . The 4 cm(-1) spectral resolution and 2.5 mu m spatial sampling facilitate the development of univariate metrics for bone development and health. Ban d integration is performed for important marker bands including phosphate v (1) at similar to 960 cm(-1), monohydrogen phosphate v(1) at similar to 100 3 cm(-1), B-type carbonate v(1) at similar to 1070 cm(-1), collagen CH2 wag at similar to 1450 cm(-1), and collagen amide I at similar to 1650 cm(-1). Mineral-to-matrix ratio, phosphate-to-monohydrogen phosphate ratio, and ca rbonate-to-phosphate ratio are calculated from these measured areas.