In the bone tissue engineering field, there is a growing interest in the application of bioactive glass scaffolds (45S5Bioglass(®)) due to their bone bonding ability, osteoconductivity and osteoinductivity. However, such scaffolds still lack some of the required functionalities to enable the successful formation of new bone, e.g. effective antibacterial properties. A large number of studies suggest that selenium (Se) has significant role in antioxidant protection, enhanced immune surveillance and modulation of cell proliferation. Selenium nanoparticles (SeNp) have also been reported to possess antibacterial as well as antiviral activities. In this investigation, uniform, stable, amorphous SeNp have been synthesized and additionally immobilized within spherical PLGA particles (PLGA/SeNp). These particles were used to coat bioactive glass-based scaffolds synthesized by the foam replica method. Samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). SeNp, 45S5Bioglass(®)/SeNp and 45S5Bioglass(®)/PLGA/SeNp showed a considerable antibacterial activity against Gram positive bacteria, Staphylococcus aureus and Staphylococcus epidermidis, one of the main causative agents of orthopedic infections. The functionalized Se-coated bioactive glass scaffolds represent a new family of bioactive, antibacterial scaffolds for bone tissue engineering applications.

Phase composition, crystal structure and morphology of biological hydroxyapatite (BHAp) extracted from human mandible bone, and carbonated hydroxyapatite (CHAp), synthesized by the chemical precipitation method, were studied by x-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and Raman (R) spectroscopy techniques, combined with transmission electron microscopy (TEM). Structural and microstructural parameters were determined through Rietveld refinement of recorded XRD data, performed using the FullProf computing program, and TEM. Microstructural analysis shows anisotropic extension along the [00l] crystallographic direction (i.e. elongated crystallites shape) of both investigated samples. The average crystallite sizes of 10 and 8 nm were estimated for BHAp and CHAp, respectively. The FTIR and R spectroscopy studies show that carbonate ions substitute both phosphate and hydroxyl ions in the crystal structure of BHAp as well as in CHAp, indicating that both of them are mixed AB-type of CHAp. The thermal behaviour and carbonate content were analysed using thermogravimetric and differential thermal analysis. The carbonate content of about 1 wt.% and phase transition, at near 790 °C, from HAp to β-tricalcium phosphate were determined in both samples. The quality of synthesized CHAp powder, particularly, the particle size distribution and uniformity of morphology, was analysed by a particle size analyser based on laser diffraction and field emission scanning electron microscopy, respectively. These data were used to discuss similarity between natural and synthetic CHAp. Good correlation between the unit cell parameters, average crystallite size, morphology, carbonate content and crystallographic positions of carbonate ions in natural and synthetic HAp samples was found.

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The aim of this study was to improve the mechanical properties and to optimize antimicrobial activity of hydroxyapatite (HAP) by simultaneous doping with Mg and Cu ions in order to obtain material that would be able to assist in the bone/tooth healing process, prevent postimplementation infections and provide satisfying values of hardness and fracture toughness for biomedical application. Ion doping was done during the hydrothermal synthesis of HAP powders, whereby the content of Mg ions in the starting solution was varied between 1-20 mol. % with regard to Ca ions, while the amount of Cu ions was kept constant at 0.4 mol. %. The green compacts were sintered for 2 h at temperatures ranging 750-1200 °C depending on the Mg content, chosen in agreement with dilatometry results. Presence of Mg ions was found to favour transition from HAP to Mg/Cu co-substituted hydroxyapatitebiocompatibility, mechanical properties and antimicrobial activity

The study is devoted to the processing of hydroxyapatite (HAp) nanopowder to develop fully dense nanostructured bioceramics by pressureless sintering. The sintering behavior of stoichiometric HAp prepared by hydrothermal processing was investigated by nonisothermal, two‐step, and conventional sintering. By low‐temperature two‐step sintering (TSS), at 900°C and 850°C, with appropriate dwell time, dense bioceramics without final‐stage grain growth and average grain size of 75 nm was obtained. A concept of master sintering curve was applied, enabling control of sintering process, estimation of effective activation energy for sintering of HAp nanopowder, and qualitative understanding of sintering mechanisms. According to estimated activation energy of 412.6 kJ/mol, low sintering temperature and particles' microstructure as the dominant sintering mechanism we proposed diffuse‐viscous flow controlled by grain boundary diffusion. HAp nanoparticles comprising of different interior and boundary regions as ordered/disordered microstructure are found to be of an advantage for low‐temperature sintering.

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Nanostructured calcium phosphate functionally graded materials (FGMs) with simultaneous gradients of density, phase composition, and mechanical properties were fabricated by consecutive uniaxial pressing of stoichiometric (SHAp) and calcium deficient (CDHAp) hydroxyapatite powders in multilayered samples and reaction sintering. During sintering procedure SHAp composition remained stable (HAp) while CDHAp was phase transformed in biphasic calcium phosphate (BCP, i.e. HAp þβ-TCP) yielding HAp/BCP FGMs. To reduce mismatch stress between adjacent layers, generated during sintering, gradient of phase composition was optimized by introducing intermediate layer(s) made from a mixture of SHAp and CDHAp in an appropriate mass ratio. Optimal processing conditions for preparation of nanostructured ceramics were provided via two-step sintering. High-quality FGMs structure, without delamination, cracks and micro-structural damages was observed by an SEM technique; moreover, a detailed examination by FE-SEM established the unidirectional (perpendicular with respect to the layers) gradual change of microstructure, from fully dense to $40% of porosity. Detailed micro-Raman and FTIR spectroscopy studies showed an increase of β-TCP amount along the FGMs height, confirming gradient of phase composition. Mechanical properties measured by microindentation revealed gradual change of microhardness from 650 to 115 HV, with simultaneous change of Young's modulus from 92 to 24 GPa.