Antibacterial properties and regenerative potential of Sr²+ and Ce³+ doped fluorapatites; a potential solution for peri-implantitis

Scaffolds and implants in orthopaedics and regenerative dentistry usually fail because of bacterial infections. A promising solution would be the development of biomaterials with both significant regenerative potential and enhanced antibacterial activity. Working towards this direction, fluorapatite was synthesised and doped with Sr²+ and Ce³+ ions in order to tailor its properties. After experiments with four common bacteria (i.e. E. Coli, S. Aureus, B. Subtilis, B. Cereus), it was found that the undoped and the Ce³+ doped fluorapatites present better antibacterial response than the Sr²+ doped material. The synthesised minerals were incorporated into chitosan scaffolds and tested with Dental Pulp Stem Cells (DPSCs) to check their regenerative potential. As was expected, the scaffolds containing Sr²+-doped fluorapatite, presented high osteoconductivity leading to the differentiation of the DPSCs into osteoblasts. Similar results were obtained for the Ce³+-doped material, since both the concentration of osteocalcin and the RUNX2 gene expression were considerably higher than that for the un-doped mineral. Overall, it was shown that doping with Ce³+ retains the good antibacterial profile of fluorapatite and enhances its regenerative potential, which makes it a promising option for dealing with conditions where healing of hard tissues is compromised by bacterial contamination.