Raman transects, microspectra taken at equal intervals along a line, are used to explore the microstructure of human cortical bone. Transects of 50 spectra taken at 2.5 μm intervals across an osteon show spatial differen ces in local mineral and protein com position as different physiological structures are traversed. Differences in mineral composition are seen near the rim of an osteon and further out in the lamellae. The blood vessel wall, primarily composed of collagen and elastin, is detected inside the Haversian canal. Factor analysis is used to explore the data set and reveals differences in mineral com position. Factor analysis also yields one bone matrix component, an osteoidal tissue component, and one blood vessel protein component. The 4 cm-1 spectral resolution and 2.5 μm spatial sampling facilitate the development of univariate metrics for bone development and health. Band integration is performed for important marker bands including phosphate ν₁ at ~ 960 cm-1 , monohydrogen phosphate ν₁ at ~ 1003 cm-1 , B-type carbonate ν₁ at ~ 1070 cm-1, collagen CH 2 wag at ~ 1450 cm-1, and collagen amide I at ~ 1650 cm-1. Mineral-to-matrix ratio, phosphate-to-monohydrogen phosphate ratio, and carbonate-to-phosphate ratio are calculated from these measured areas.
Keywords:
Raman spectroscopy; Raman transect; Cortical bone; Osteon; Factor analysis; Hydroxyapatite; Collagen; Blood vessel