Towards refining Raman spectroscopy-based assessment of bone composition

Abstract

Abstract 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 $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 1 -, $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 2 -, $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 3 -, $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 4 PO 4 3− , and $$\nu_{1} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>ν</mml:mi><mml:mn>1</mml:mn></mml:msub></mml:math> CO 3 2− bands represent the inorganic phase while amide I, amide III, Proline, Hydroxyproline, Phenylalanine, δ(CH 3 ), δ(CH 2 ), and $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> (C–H) represent the organic phase. Here, using high-resolution Raman spectroscopy, it is demonstrated that all PO 4 3− 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 $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 2 PO 4 3− 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 $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 4 PO 4 3− band broadening. In the 1020–1080 cm −1 range, the ~ 1047 cm −1 $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 3 PO 4 3− sub-component is obscured by the 1033 cm −1 Phenylalanine peak, while the ~ 1076 cm −1 $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 3 PO 4 3− sub-component is masked by the $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 1 CO 3 2− band. With $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 1 PO 4 3− peak broadening, $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 2 PO 4 3− integral area increases exponentially and individual peaks comprising the $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 4 PO 4 3− band merge together. Therefore, $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 2 PO 4 3− and $$\nu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ν</mml:mi></mml:math> 4 PO 4 3− band profiles are sensitive to changes in mineral crystallinity.

Topics & Concepts