# Vibrational fingerprintings for chemical recognition of biominerals

## TL;DR

This study uses first principles calculations to analyze the complete vibrational spectra of apatite biominerals, enhancing chemical recognition for biomedical diagnostics via non-invasive spectroscopies.

## Contribution

It provides a detailed vibrational spectral reference for apatite biominerals, considering the entire phonon spectrum and environmental effects, which was previously limited to phosphate groups.

## Key findings

- Identified unique vibrational features for different apatite types.
- Demonstrated the impact of local environment on vibrational spectra.
- Established a reference for non-invasive biomedical spectroscopy.

## Abstract

Pathologies associated with calcified tissue, such as osteoporosis, demand in vivo and/or in situ spectroscopic analysis to assess the role of chemical substitutions in the inorganic component. High energy X-ray or NMR spectroscopies are often impractical or damaging in biomedical conditions. Low energy spectroscopies, such as IR and Raman techniques, are often the best alternative. In apatite biominerals, the vibrational signatures of the phosphate group are generally used as fingerprint of the materials although they provide only limited information. Here, we have used first principles calculations to unravel the complexity of the complete vibrational spectra of apatites. We determined the spectroscopic features of all the phonon modes of fluor-apatite, hydroxy-apatite, and carbonated fluoroapatite beyond the analysis of the phosphate groups, focusing on the effect of local corrections induced by the crystalline environment and the specific mineral composition. This provides a clear and unique reference to discriminate structural and chemical variations in biominerals, opening the way to a widespread application of non-invasive spectroscopies for in vivo diagnostics, and biomedical analysis.