No abstract

Ionic trace elements such as Mg 2+ , Mn 2+ and Sr 2+ are very difficult to stabilize in the hydroxyapatite lattice, and they can induce phase transformations when subjected to thermal treatments. The effects of the ions themselves are often confused with the effects of the newly formed phases. Therefore, the objective of this work was to evaluate the effects of the ions isolated from the effects caused by the inherent phase transformations observed in these systems. WDXRF, XRD, FTIR and biological assays using mouse preosteoblastic cells (MC3T3-E1) showed the Mg 2+ ions can stimulate cell differentiation even when segregated from the HA structure in the form of MgO. However, the presence of MgO considerably retards cell proliferation. At the same time, Mn 2+ ions are able to increase cell proliferation and induce the production of high levels of ALP, regardless of whether they are inserted into the HA structure or segregated in the form of Mn 3 O 4. Finally, the presence of Sr 2+ in the HA lattice does not appear to directly affect cell behavior, since both the proliferation and production of ALP are comparable to those observed in the nondoped HA sample.

No abstract

Bioceramics synthesized in laboratories must undergo biological tests that consider the final format and all the processing steps involved in the production of the final device. However, in many cases, the synthesized materials are characterized in formats very different from those that will ultimately be implanted into the body. Once living cells are directly cultured on surfaces, a mismatch between bulk and surface microstructural characterizations often leads to the misinterpretation of biological responses. Therefore, our objective in this work was to determine whether and at what level significant microstructural changes can occur between the surface and the bulk of hydroxyapatite pellets produced by uniaxial pressing followed by calcination. Our results showed that the as-synthesized hydroxyapatite crystals had a preferential orientation along the [0 0 1] direction. The calcination process followed by grain growth inhibited this texture feature. However, on the pellet surfaces, the initial orientation was preserved. At the same time, crystallite growth was inhibited, and the cell unit volume of the crystals on the surface was significantly lower than that of the crystals in the bulk. These results demonstrated that the crystallographic features on the surface of hydroxyapatite pellets can be completely different from those observed for the bulk.