The physicochemical properties and biological behavior of sintered-bovine-derived hydroxyapatite (BHAp) are here reported and compared to commercial synthetic-HAp (CHAp). Dense ceramics were sintered for 2 h and 4 h at 1200 °C to investigate their microstructure–structure–in-vitro behavior relationship for both HAp ceramics. Densification was directly proportional to sintering time, showing a grain coarsening behavior with a greater effect on BHAp. Lattice parameters, crystallite size, cell volume and Ca/P ratio were determined by Rietveld refinement of X-ray diffraction (XRD) patterns using GSAS®. Ionic substitutions (Na+, Mg2+, CO32−) related to BHAp structure were associated with their position changes in the vibrational modes and correlated with the structural parameters obtained from the XRD analysis. Variations in the structural parameters and surface morphology were also evaluated after different soaking periods in simulated body fluid, which is associated with the formation of bone-like apatite layer and thus bioactivity. Mitochondrial activity (MTS) and lactate dehydrogenase (LDH) assays showed that the material released by the ceramics does not induce toxicity after exposure in human fetal osteoblastic (hFOB) cells. Furthermore, no statistically significant differences were found between the HAp obtained from different sources. These results show that BHAp can be used with no restrictions for the same biomedical applications as CHAp.

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The morphological, structural and chemical transformations during the biomineralization process associated with the apatite formation from bovine-derived hydroxyapatite (BHAp) and BHAp/Nagelschmidtite composite obtained from the mixture of BHAp and Vitryxx® bioactive glass are here presented. The study is focused on the structural characteristics of apatite formation and maturation process taking place at the biomaterial surface. The use of a biological HAp is of interest aiming to mimic the natural process of bone mineral matrix formation in the crystallization mechanism. This process was characterized by transmission electron microscopy (TEM), where the initial stage was identified as the formation of a hydrated amorphous matrix followed by the appearance of randomly oriented nanocrystals that later coalesce and grow with preferred orientation to c-axis. This behavior is a biomimetic process based on the alignment of natural bone apatite along collagen fibrils. The understanding of natural processes of mineral matrix formation at micro and nanoscale levels on bioactive materials is of great interest to address the effect of size, structure, and composition of apatite nanocrystals on the biologic phenomena involved in osseointegration.

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