Bone quality characteristics obtained by Fourier transform infrared and Raman spectroscopic imaging

Background

Bone strength, which is an indicator of the risk of fracture, is determined by bone mass (bone mineral density, 70%) and bone quality (30%). Bone quality results from a combination of various material and structural properties, making it difficult to determine a suitable method for the evaluation of bone quality based on clinical measurements. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy are powerful techniques for the assessment of bone quality and reveal similar information on molecular structures; however, this molecular information is based on different physical phenomena. Therefore, a comparison of FTIR and Raman spectra is required for an accurate assessment of bone quality.

Highlight

We previously assessed the bone quality of femurs from rats with chronic kidney disease (CKD) using FTIR imaging, and found the carbonate-to-phosphate ratio in the hydroxyapatite was significantly reduced compared to control rats; however, there was no difference in crystallinity. Therefore, we focused on the crystallinity of the femoral cortical bone in rats with CKD, and compared the PO₄^3- bands in FTIR spectra in detail with those in the Raman spectra.

Conclusion

The PO₄^3- bands in the FTIR spectra were affected by changes in calcium phosphate composition rather than by changes in crystal size. Thus, FTIR is more suitable for the evaluation of mineral maturity than crystallinity; Raman spectroscopy is more sensitive to crystallinity than FTIR.