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The present study is aimed at investigating the contribution of two biologically important cations, Mg(2+) and Sr(2+), when substituted into the structure of hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2),HA). The substituted samples were synthesized by an aqueous precipitation method that involved the addition of Mg(2+)- and Sr(2+)-containing precursors to partially replace Ca(2+) ions in the apatite structure. Eight substituted HA samples with different concentrations of single (only Mg(2+)) or combined (Mg(2+) and Sr(2+)) substitution of cations have been investigated and the results compared with those of pure HA. The obtained materials were characterized by X-ray powder diffraction, specific surface area and porosity measurements (N(2) adsorption at 77 K), FT-IR and Raman spectroscopies and scanning electron microscopy. The results indicate that the co-substitution gives rise to the formation of HA and β-TCP structure types, with a variation of their cell parameters and of the crystallinity degree of HA with varying levels of substitution. An evaluation of the amount of substituents allows us to design and prepare BCP composite materials with a desired HA/β-TCP ratio.

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ABSTRACT:Two series of glasses of general formula (2-p) SiO 2 Á1.1Na 2 OÁCaOÁpP 2 O 5 ÁxZnO ( p ¼ 0.10, 0.20; x ¼ 0.0, 0.16, 0.35, and 0.78) have been analyzed for physico-chemical surface features before and after contact with simulated body fluid, morphological characteristics, and osteoblastlike cells behavior when cultured on them. The resulted good cell adhesion and growth, along with nonsignificant changes of the focal contacts, allow the authors to indicate HZ5 and HP5Z5 glasses as the ones having optimal ratio of Zn/P to maintain acceptable cell behavior, comparable to the bioactive glass (Bioglass Õ ) used as a control; results are also rationalized by means of three-dimensional models derived by molecular dynamic simulations, with decomposition and conversion rates optimized with respect to the parent Hench's Bioglass Õ .

The vapor-phase deposition of triethoxy(octyl)-silane and 1H,1H,2H,2H-perfluoroctyltriethoxysilane on silica substrates was studied at different temperatures (70−150°C). An original combination of spectroscopic ( 13 C and 29 Si solid state NMR, FTIR), electrochemical (CV, EIS), and surface (surface free energy determinations, AFM) characterization techniques was adopted to shed light on the role played by the alkylsilane structure and deposition temperature on the resulting layer. As for the unfluorinated molecule, both wettability and ion permeability displayed a bell-shaped curve with respect to the functionalization temperature. Spectroscopic techniques showed similar trends in the functionalization degree and suggested the formation of oligomers/polymers covalently attached to the surface. 29 Si NMR proved that higher functionalization temperatures increase lateral polymerization across the alkylsilane layer. Conversely, the wettability was almost invariant with the functionalization temperature for the fluorinated analogue. However, electrochemical and spectroscopic results had a significant dependence on the functionalization conditions, even more marked than for the unfluorinated alkylsilane. The higher thermal reactivity of fluorinated molecules led to vertical polymerization, as supported by very high water contact angles, diffusion components in EIS, and a lower degree of covalent bonding with the surface. Optimal deposition conditions were identified at 100 and 90°C for the unfluorinated and fluorinated alkylsilane, respectively.