WEB Bio-hydroxyapatite powders: Effects of biogenic sources and processing methodologies on physicochemical properties and bioactive response
Bio-hydroxyapatite (BHAp) is a material commonly used as an osteogenic scaffold in biomedical applications. Various physical, chemical, and biological studies have been conducted to obtain a biomaterial similar to the mineral part of the bone. Nevertheless, to the author's knowledge, a thorough investigation comparing changes in BHAp properties as a function of its obtention procedures and sources has not been reported yet. This study shows a comparison of the BHAp powder obtained from bovine and porcine bones using two methodologies, which were compared to determine the influence of the obtention process on BHAp properties. Powders specimens of both methods underwent structural and microstructural characterizations, finding that functional groups associated with fat and proteins like aldehyde, methylene, and amine decreased with precleaning treatments in both methodologies. Despite the differences between the processing methods, the results obtained suggest that the thermal treatment has a meaningful influence on the phases formed during the acellular in-vitro test. Particularly, the thermal treatments performed (1100 °C for 2 h and 800 °C for 24 h for A and B methodologies, respectively) resulted in a hydroxyapatite crystal phase formation as the main phase with the presence of magnesium oxide (MgO) and calcium oxide (CaO) as secondary phases in both methods. Also, the B method presents higher carbonate groups content (CO3-2) and type A and B substitutions compared to the A method. We found that the changes in carbonate groups can be attributed to the temperature used in the thermal treatment. Subsequently, the BHAp samples were immersed in Hank Solution during 3, 7, 14, 21, and 28 days to study the bioactivity response. We found a bone-like apatite layer formation at the surface as a function of the soaking time in all sets of samples, as were expected. However, we also found a calcite layer grown at the surface of the samples prepared by method B. Finally, in this contribution, a complete discussion explained the phenomena responsible for the precipitation of the unexpected phases is conducted in detail.