Towards refining Raman spectroscopy-based assessment of bone composition.

Various compositional parameters are derived using intensity ratios and integral area ratios of different spectral peaks and bands in the Raman spectrum of bone. The [Formula: see text]1-, [Formula: see text]2-,[Formula: see text]3-, [Formula: see text]4 PO43-, and [Formula: see text] CO32- bands represent the inorganic phase while amide I, amide III, Proline, Hydroxyproline, Phenylalanine, δ(CH3), δ(CH2), and [Formula: see text](C-H) represent the organic phase. Here, using high-resolution Raman spectroscopy, it is demonstrated that all PO43- bands of bone either partially overlap with or are positioned close to spectral contributions from the organic component. Assigned to the organic component, a shoulder at 393 cm-1 compromises accurate estimation of [Formula: see text]2 PO43- integral area, i.e., phosphate/apatite content, with implications for apatite-to-collagen and carbonate-to-phosphate ratios. Another feature at 621 cm-1 may be inaccurately interpreted as [Formula: see text]4 PO43- band broadening. In the 1020-1080 cm-1 range, the ~ 1047 cm-1 [Formula: see text]3 PO43- sub-component is obscured by the 1033 cm-1 Phenylalanine peak, while the ~ 1076 cm-1 [Formula: see text]3 PO43- sub-component is masked by the [Formula: see text]1 CO32- band. With [Formula: see text]1 PO43- peak broadening, [Formula: see text]2 PO43- integral area increases exponentially and individual peaks comprising the [Formula: see text]4 PO43- band merge together. Therefore, [Formula: see text]2 PO43- and [Formula: see text]4 PO43- band profiles are sensitive to changes in mineral crystallinity.