Spatial Distribution of Phosphate Species in Mature and Newly Generated Mammalian Bone by Hyperspectral Raman Imaging

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Abstract
Hyperspectral Raman images of mineral components of trabecular and cortical bone at 3 µm spatial resolution are presented. Contrast is generated from Raman spectra acquired over the 600–1400 cm?1 Raman shift range. Factor analysis on the ensemble of Raman spectra is used to generate descriptors of mineral components. In trabecular bone independent phosphate (PO4?3) and monohydrogen phosphate (HPO4?2) factors areobserved. Phosphate and monohydrogen phosphate gradients extend from trabecular packets into the interior of a rod. The gradients are sharply defined in newly regenerated bone. There, HPO4?2 content maximizes near a trabecular packet and decreases to a minimum value over as little as a 20 µm distance. Incomplete mineralization is clearly visible. In cortical bone, factor analysis yields only a single mineral factor containing both PO4?3 and HPO4?2 signatures and this implies uniform distribution of these ions in the region imaged.Uniform PO4?3 and HPO4?2 distribution is verified by spectral band integration.