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To assess the application potential of novel biomaterials, their behaviour in model media and upon sterilization should be investigated, as well as the stability related to their storage conditions. Such data are lacking for Mg-substituted HAP (Mg-HAP). Therefore, the changes in the local structure of non-substituted and Mg-HAP after irradiation and immersion in corrected simulated fluid and saline solution for 28 days were followed by electron paramagnetic resonance (EPR) spectroscopy for the first time. To better understand the stability of radical species induced by sterilization, EPR spectra of samples kept for 2 h at temperatures up to 373 K were recorded to provide an insight into the stability of the sample storage conditions by the accelerated aging method. Samples were characterized by PXRD, FTIR, SEM, EDS, AAS and TGA. Results confirmed that irradiation does not induce changes in the composition or the structure of any of the investigated materials. Fading or the complete disappearance of radical signals in the EPR spectra after immersion in both media was accompanied by the disappearance of other phases formed as a minor byproduct in the synthesis of substituted HAP, as confirmed by PXRD and FTIR analysis. Obtained results confirm the great potential of Mg-HAPs for biomedical applications, although closer attention should be given to the processes related to sample storage stability at different temperatures.

Abstract Biomimetic bone apatite coatings were realized for the first time by the novel Ionized Jet Deposition technique. Bone coatings were deposited on titanium alloy substrates by pulsed electron ablation of deproteinized bovine bone shafts in order to resemble bone apatite as closely as possible. The composition, morphology and mechanical properties of the coatings were characterized by GI-XRD, FT-IR, SEM-EDS, AFM, contact angle measurements, micro-scratch and screw-insertion tests. Different post-treatment annealing conditions (from 350 °C to 425 °C) were investigated. Bone apatite coatings exhibited a nanostructured surface morphology and a composition closely resembling that of the deposition target (i.e. natural bone apatite), also regarding the presence of magnesium and sodium ions. Crystallinity and composition of the coatings were strongly influenced by annealing temperature and duration; in particular, upon annealing at 400 °C and above, a crystallinity similar to that of bone was achieved. Finally, adhesion to the titanium substrate and hydrophilicity were significantly enhanced upon annealing, all characteristics being known to have a strong positive impact on promoting host cells attachment, proliferation and differentiation. Highlights • Biomimetic thin films were obtained by pulsed electron deposition. • Films obtained exhibit composition perfectly resembling the deposition targets. • Film crystallinity is tuned by post heating treatment up to resembling that of bone. • Upon annealing, high adhesion and good hydrophilicity can also be obtained. [ABSTRACT FROM AUTHOR]

Several trace elements such as Mg2+, Na+, K+, F−, Cl− are contained in biological apatite of natural bones. The presence of these elements in bones is indispensable for their calcification and mineralization. Their simultaneous insertion in the apatite framework with preserved structure was our aim. Therefore, calcium hydroxyapatite (HAp) biomaterials doped with the aforementioned ions was the subject of the present study. Three formulations of ion-substituted HAp powders were prepared via a wet-chemical precipitation method. Analysis and characterization by several techniques proved that the obtained powders were of apatitic nature. Although stoichiometry was slightly weaker, multiple ion-substitutions lead to stable structures. When sintering, calcined powders at 500 °C for 1 h were uniaxially isostatically cold compacted into pellets. These pellets were pressurelessly sintered in a temperature range of 900-1250 °C. The maximum 95% densification value was obtained with the samples sintered at temperature 1150 °C for 1 h. A secondary phase of β-Ca3(PO4)2 appeared at 730 °C related to partial decomposition of the apatitic phase. The sintered materials were mechanically characterized by measurements of compressive and flexural strengths, fracture toughness, Young's modulus and microhardness and the maximum values were obtained as 154 MPa, 60 MPa, 1.55 MPa·m1/2, 151 GPa and 600 Hv, respectively. [ABSTRACT FROM AUTHOR]

Infection in primary total joint prostheses is attracting considerable attention. In this study, silver (Ag) was incorporated into hydroxyapatite (HA) using a hydrothermal method in order to improve its antimicrobial properties. Strontium (Sr) was added as a second binary element to improve the biocompatibility. The substituted HA samples were fixed on titanium (Ti) substrates by dopamine-assisted immobilization in order to evaluate their antibacterial and biological properties. The results showed that Ag and Sr were successfully incorporated into HA without affecting their crystallinity. Further, the antibacterial tests showed that all the Ag-substituted samples had good anti-bacterial properties against Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ). Despite their good antibacterial ability, the Ag-substituted samples showed evidence of cytotoxicity on MG63 cells, characterized by low cell density and poor spreadability. The addition of Sr to the Ag-substituted samples considerably reduced the cytotoxicity of Ag. Although the viability of the cells grown on the surfaces of co-substituted HA was not as high as that of the cells grown on the HA surfaces, it is believed that excellent antibacterial properties and good biological activity can be achieved by balancing the dosage of Sr and Ag. [ABSTRACT FROM AUTHOR]

In the present study, the effects of variable amounts of Yb addition on the structural, thermal, and in vitro biocompatibility properties of Ce-doped hydroxyapatite (HAp) samples synthesized via the wet chemical method were investigated. Besides, the prepared formulations were also modeled for making the theoretical investigations. The single-phase compositions were detected for all samples, and no formation of additional phases was observed. Doping with Yb was observed to produce some variations in the lattice parameters, unit cell volume, lattice strain, and lattice stress. While a decreasing trend in the crystallite size and crystallization percent with increasing Yb content was found, a gradual increase in the anisotropic energy density was observed. All samples were found to be thermally stable from room temperature to 1000 °C with negligible mass losses during heating. No significant morphological changes were caused by the addition of Yb. For all samples, the numerical values of (Ca + Ce + Yb)/P molar ratio were found to be close to that for stoichiometric HAp (1.67). It was observed that the increased Yb additive caused a decrease in cell viability values. A continuous decrease in the bandgap energy with the increasing amounts of Yb added to the Ce-based HAp structure was observed from the theoretical investigations. A sharp decrease in the cell viability of the Ce-based HAp was observed with the addition of Yb. • Ce/Yb co-doped hydroxyapatites were investigated for the first time. • The bandgap decreased gradually with the increasing amount of Yb. • Addition of Yb decreased the cell viability of the Ce-based hydroxyapatites. [ABSTRACT FROM AUTHOR]