Studies on bone metabolism by using isotope microscopy, FTIR imaging, and micro-Raman spectroscopy

Abstract

We describe the comprehensive analysis of bone quality by using the isotope microscopy, Fourier transform infrared (FTIR) imaging, and Raman spectroscopy, which are non-destructive techniques. Isotope microscopy is a novel tool for visualizing microdomains within materials through the imaging of the 3-dimensional distribution of isotopes. This technique enabled us to observe calcium metabolism in the tibiae of mice. Thus, a stable calcium isotope fed to mice was observed in the trabecular and cortical bones. FTIR and Raman spectroscopies are powerful tools for characterizing the chemical compositions of materials and provide both qualitative and quantitative information on molecular structure. An FTIR imaging system, which is an accessory for FTIR spectroscopy, provides a distribution map of functional components in the sample. The crystallinity, secondary structure of collagen, carbonate-to-phosphate ratio, and mineral-to-matrix ratio of bone can be obtained from the IR spectra extracted from the selected area of an FTIR image. Raman spectroscopy complements FTIR spectroscopy; however, the Raman spectrum provides information about functional groups in a sample as well as its FTIR spectrum. The major advantage of Raman spectroscopy for bone analysis is the ability to obtain spectra with higher spatial resolution compared with those acquired using FTIR spectroscopy. Moreover, a wide range of samples, including aqueous solutions, fibers, powders, or frozen materials can be readily analyzed, without any special preparation. Raman spectroscopy generates data on crystallinity, carbonate-to-phosphate ratio, and mineral-to-matrix ratio in bone.