Abstract
Biological apatite mineral is highly substituted with carbonate (CO32−). CO32− can exchange for either phosphate, known as B-type, or hydroxyl groups, known as A-type. Although the former has been extensively studied, A-type CO32− substituted apatites are poorly understood. Therefore, A-type CO32− apatites with biologically relevant levels of CO32− (1.7–5.8 wt%) were prepared and characterized. The addition of A-type CO32− into the apatite structure caused the predicted expansion of the a-axis and contraction of the c-axis in the unit cell. This was accompanied by a significant modification in the atomic order, especially along the a-axis plane, and crystallite size. A combination of in situ loading with synchrotron X-ray Diffraction and Density Functional Theory showed that increasing A-type CO32− substitutions also reduced the bulk and elastic moduli of the crystals. These results show that although A-type CO32− may inhibit lattice changes caused by B-type CO32−, A-type CO32− enhances the reduction in crystal order and mineral stiffness. These results help us to identify the possible contributions of A-type CO32− substitutions in biological apatites that contain both A- and B-type CO32−. In addition, this implies that the stiffness of bioapatite may change with increasing A-type CO32− substitutions, potentially altering the fracture mechanics of calcified tissues and biomaterials.
| Original language | English |
|---|---|
| Article number | 106962 |
| Journal | Journal of the Mechanical Behavior of Biomedical Materials |
| Volume | 166 |
| DOIs | |
| State | Published - Jun 2025 |
Funding
We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at Petra III and we would like to thank Norbert Schnell for assistance in using beamline P07. Beamtime was allocated for proposal I-20220348. We would also like to acknowledge Christian Rey from CIRIMAT, France, for his support with the preparation of the A-type CO32− apatites. SW was funded by the Chateaubriand Fellowship for her A-type CO32− apatite synthesis work in CIRIMAT, Toulouse, France. Partial paper synthesis and writing by SW was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. Funding was provided by NSF CAREER grant 2044870 and DEPSCoR grant FA9550-23-1-0493 for ACD. AKN would like to acknowledge the grant NSF 2323499. ALE would also like to acknowledge the computational resources provided by the AHPCC. We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at Petra III and we would like to thank Norbert Schnell for assistance in using beamline P07. Beamtime was allocated for proposal I-20220348. We would also like to acknowledge Christian Rey from CIRIMAT, France, for his support with the preparation of the A-type CO 3 2- apatites. SW was funded by the Chateaubriand Fellowship for her A-type CO 3 2- apatite synthesis work in CIRIMAT, Toulouse, France. Partial paper synthesis and writing by SW was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. Funding was provided by NSF CAREER grant 2044870 and DEPSCoR grant FA9550-23-1-0493 for ACD. AKN would like to acknowledge the grant NSF 2323499. ALE would also like to acknowledge the computational resources provided by the AHPCC.
Keywords
- Apatite
- Bone mineral
- Lattice structure
- Mechanics
- Substitutions