O objetivo deste estudo foi avaliar as características físico-químicas de 3 biomateriais bovinos inorgânicos mineralizados e correlacioná-los com a taxa de dissolução. Bio-Oss(r), Genox Inorgânico(r) e Bonefill(r) foram caracterizados por microscopia eletrônica de varredura com fonte de emissão por efeito de campo (MEV-FEG), espectroscopia de infravermelho com transformada de Fourier (FTIR), difração de raios-X (DRX), área superficial específica (BET), razão molar cálcio/fósforo e análise da dissolução. Bio-Oss(r) mostrou uma estrutura micro e nanoporosa consistindo de cristalitos de hidroxiapatita (HA) de 15 nm; Genox(r), uma estrutura microporosa composta de cristalitos de HA de 39 nm e Bonefill(r), estrutura micro e nanoporosa com tamanho indeterminável de cristalito. Análises de FTIR mostraram que Bio-Oss(r) e Genox(r) eram compostos por fosfato de cálcio. As bandas de absorção de fosfato encontraram-se pouco definidas no Bonefill(r). Por DRX, Bio-Oss(r) mostrou picos relacionados à HA carbonatada, enquanto Genox(r) somente apresentou picos correspondentes à HA; as bandas alargadas no Bonefill(r) indicaram baixa cristalinidade. Bio-Oss(r) apresentou maior área de superfície e taxa de liberação de cálcio quando comparado ao Genox(r). Embora todos os biomateriais fossem de origem bovina, os diferentes processos de manufatura resultam em materiais com diferentes propriedades físico-químicas e podem influenciar a resposta biológica e clínica.

The aim of this study was to evaluate the physicochemical characteristics of 3 mineralized bovine inorganic biomaterials and correlate them with the dissolution rate. Bio-Oss(r), GenoxInorgânico(r), and Bonefill(r) were examined using field emission gun scanning electron microscopy (FEG-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), specific surface area (BET), calcium/phosphorous molar ratio and a dissolution assay. Bio-Oss(r) showed a micro- and nanoporous structure consisting of 15-nm hydroxyapatite (HA) crystallites; Genox(r), a microporous structure composed of 39-nm HA crystallites; and Bonefill(r), micro- and nanoporous structure of indeterminable crystallite size. FTIR analysis showed that Bio-Oss(r) and Genox(r) were composed of calcium phosphate. The absorption bands of phosphate were poorly defined in Bonefill(r). By XRD, Bio-Oss(r) was shown to contain peaks related to the carbonated HA, whereas Genox(r) only contained peaks corresponding to HA. The broad bands in Bonefill(r) indicated low crystallinity. Bio-Oss(r) showed a greater surface area and calcium release rate than that of Genox(r). Although all biomaterials were of bovine origin, the different manufacturing processes result in materials with different physicochemical properties and may influence the biological and clinical response.

Hydroxyapatite-collagen (HA/Col) composites are potential scaffolds for bone tissue engineering. In this work, three-dimensional (3-D) HA/Col (50/50 wt. (%)) scaffolds were synthesized using a self-assembly method and cross-linked with a 0.125% glutaraldehyde solution. Scaffolds were evaluated in vitro by cytotoxicity testing using MC3T3 cells; proliferation and differentiation were studied using STRO-1A human stromal cells for up to 21 days. Morphological and histological examinations showed a fibrous structure with a good distribution and homogeneous HA particles distribution. By thermogravimetric analysis, a ratio of 1.2 between inorganic and organic phase was found. The scaffolds presented no cytotoxicity when evaluated using three different parameters of cell survival and integrity: 2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl] -2H-tetrazolium-5-carboxanilide (XTT), Neutral Red (NR) and Crystal Violet Dye Elution (CVDE). STRO-1A cells were found to adhere, proliferate and differentiate on the 3-D scaffold, but limited cell penetration was observed.

The crystal structure of a synthetic AB-type carbonate apatite sample was analyzed by Rietveld refinement including a model with carbon atom not fixed in the B-site of the apatite structure. Only one constraint was applied to this model: the fractional occupancies of the atoms in the CO3 ion plus PO4 ion were equal 1.0 per phosphate site with six sites per unit cell. Rietveld refinement of the crystal structure with space group P6(3)/m results in cell parameters a = 9.3583(1) Å and c = 6.9226(5) Å; Z =1; Rwp = 0.0824 and 9.5 wt. (%) of carbonate in this structure. The use of simple geometry formulas showed that the C atom is not located at the center of the equilateral triangle of oxygen O2, O3 and O3', but to a distance 0.18 Å of this triangle. The results seem to indicate a new 3-D crystal structure of the carbonated apatite in PO4 groups.

A sample of hydroxyapatite was synthesized and its crystalline structure was analyzed by X-ray diffraction by means of the Rietveld method. Two functions were used to fit the peak profiles, modified Voigt (TCHZ) and Pearson VII. The occupational factors and lattice parameters obtained by both models show that the sample does not contain relevant cationic substitutions. The interatomic distances from Ca1 to oxygens O1, O2 and O3 were adequate for a pure hydroxyapatite without defect at site Ca1. Besides, the use of multiple lines in planes (300) and (002) associated with the model Pearson VII resulted in good agreement with the TCHZ model with respect to the size-strain effectswith an ellipsoidal shape of crystallites. In conclusion, the procedures adopted in the synthesis of hydroxyapatite produced a pure and crystalline material. The experimental results of transmission electron microscopy confirmed the predicted shape of crystals.