Abstract
The Eu3+ and Sr2+ ions co-doped hydroxyapatite nanopowders (Ca10(PO4)6(OH)2) were synthesized via a precipitation method and post heat-treated at 500 °C. The concentration of Eu3+ ions was established in the range of 0.5–5 mol% to investigate the site occupancy preference. The concentration of Sr2+ ions was set at 5 mol%. The structural and morphological properties of the obtained materials were studied by an X-ray powder diffraction, a transmission electron microscopy techniques and infrared spectroscopy. As synthesized nanoparticles were in the range of 11–17 nm and annealed particles were in the range of 20–26 nm. The luminescence properties in dependence of the dopant concentration and applied temperature were investigated. The 5D0 → 7F0 transition shown the abnormally strong intensity for annealed materials connected with the increase of covalency character of Eu3+–O2− bond, which arise as an effect of charge compensation mechanism. The Eu3+ ions occupied three possible crystallographic sites in these materials revealed in emission spectra: one Ca(1) site with C3 symmetry and two Ca(2) sites with Cs symmetry arranged as cis and trans symmetry. The antibacterial properties of Eu3+ and Sr2+ ions doped and co-doped hydroxyapatite nanopowders were also determined against Gram-negative pathogens such as Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli. Obtained results suggest that both europium and strontium ions may implement antibacterial properties for hydroxyapatites. In the most cases, better antibacterial effect we noticed for dopants at 5 mol% ratio. However, the effect is strongly species- and strain-dependent feature.
Highlights
Progressive loss of bones mineral density leads to changes in bone architecture and higher probability of fractures
The crystal characterization of the Ca10(PO4)6(OH)2 doped with Sr2+, doped with Eu3+ and co-doped with 5 mol% Sr2+ and xEu3+ ions nanocrystals as-prepared and annealed at 500 °C was done by means of the powder XRD measurements
The quality of structural refinement was checked by R-values (Rw, Rwnb, Rall, Rnb, and σ) which were applied to obtain a structural refinement with better quality and reliability
Summary
Progressive loss of bones mineral density leads to changes in bone architecture and higher probability of fractures. The properties of hydroxyapatite have been still improved through obtaining appropriate grain size and morphology, adding some dopants such as Sr2+, Mg2+, Zn2+, F−, CO32−, which are naturally built into the human bone tissue, and achieve special role in homeostasis. Due to this, these doping agents can improve the biological response of an organism. There have been investigated the preparation of the nanohydroxyapatite Ca10(PO4)6(OH) doped with Eu3+ and Sr2+ ions as structurally modified biomaterial to promote bone regeneration process (hydroxyapatite) and to enable bio-imaging (Eu3+) with additional antibacterial properties (Eu3+ and Sr2+) for theranostics application
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