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Abstract: Physicochemical properties of hydroxyapatite (HAP) synthesized by neutralization method are heavily dependent on the process variables. A Plackett–Burman two-level experimental design was therefore, chosen to screen a large number of variables and to determine their effect on HAP characteristics. The sorption of cadmium ions on HAP was studied as well. Of six selected variables (temperature, mixing speed, reactant concentration, addition rate, presence of inert atmosphere and aging time), temperature has shown the strongest influence on HAP structural and sorption properties. Smaller crystallites, lower crystallinity and higher specific surface area lead to higher sorption of cadmium ions. Room temperature and no aging are preferable conditions for the synthesis of HAP with the highest sorption efficiency. [Copyright &y& Elsevier]

Highlights: [•] The synthesis of fluorine substituted hydroxyapatite samples was done by a neutralization, which consists of adding the solution of HF and H3PO4 in suspension of Ca(OH)2. [•] Particles of fluorine substituted hydroxyapatite samples are of nano size. [•] The central composite design was used in order to determine the optimal conditions for the antimicrobial activity of the synthesized samples against Streptococcus mutans. [•] Antimicrobial activity of the samples increases with the increase of fluoride concentration and the decreased pH of saline. [ABSTRACT FROM AUTHOR]

Abstract: Monophase silver-doped hydroxyapatite (Ag x Ca10−x (PO4)6(OH)2; 0.002≤ x ≤0.04) nanoparticles were prepared using a neutralization method and investigated with respect to potential medical applications. This method consists of dissolving Ag2O in solution of H3PO4, and the slow addition to suspension of Ca(OH)2 was applied for the purpose of homogenous distribution of silver ions. Characterization studies from XRD, TEM and FTIR spectra showed that obtained crystals are monophase hydroxyapatites and that particles of all samples are of nano size, with average length of 70nm and about 15–25nm in diameter. Antimicrobial studies have demonstrated that all silver-doped hydroxyapatite samples exhibit excellent antimicrobial activity in vitro against the following pathogens: Staphylococcus aureus, Escherichia coli and Candida albicans. The hydroxyapatite sample with the highest content of silver has shown the highest antimicrobial activity; killed all cells of E. coli and brought to more than 99% reduction in viable counts of S. aureus and C. albicans. The atomic force microscopic studies illustrate that silver-doped hydroxyapatite sample causes considerable morphological changes of microorganism cells which might be the cause of cells’ death. Hemolysis ratios of the silver-doped hydroxyapatite samples were below 3%, indicating good blood compatibility and that are promising as biomaterials. [ABSTRACT FROM AUTHOR]

Abstract: Antimicrobial materials based on hydroxyapatite are potentially attractive in a wide variety of medical applications. The synthesis of copper and zinc-doped hydroxyapatite was done by neutralization method. This method consists of dissolving CuO or ZnO in solution of H3PO4, and the slow addition to suspension of Ca(OH)2 for obtaining monophasic product. Characterization studies from XRD, SEM, TEM and FTIR spectra showed that particles of all samples are of nano size and they do not contain any discernible crystalline impurity. The quantitative elemental analysis showed that the copper and zinc ions fully incorporated into the hydroxyapatite. The antimicrobial effects of doped hydroxyapatite powders against pathogen bacterial strains Escherichia coli, Staphylococcus aureus and pathogen yeast Candida albicans were tested in solid and liquid media. Quantitative test in liquid media clearly showed that copper and zinc-doped samples had viable cells reduction ability for all tested strains. [Copyright &y& Elsevier]