Efeitos da inserção simultânea dos íons Mg2+, Mn2+ e Sr2+ sobre hidroxiapatita em processo de precipitação e troca iônica

• Autor(a) principal: Silva, Leila Melo da
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: http://ri.ufs.br/jspui/handle/riufs/11303
• topic: Ciência dos materiais; Hidroxiapatita; Troca iônica; Osteoblastos; Precipitação (Química); Dopagem; Hydroxyapatite; Doping; Osteoblast; Precipitation; Ion exchange; ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA

The Mg2+, Mn2+ and Sr2+ ions are of great biological interest in association with hydroxyapatite (HA) for inducing positive cellular responses in bone regeneration. However, these ions are difficult to stabilize in the crystal lattice of HA synthesized by co-precipitation, generally inducing phase transformations during thermal treatments above 800°C. The new phases are rarely taken into account when these materials are tested with cells. In many cases, the effects attributed to one element in substituted HA are mixed with those caused by the presence of unaccounted phases. Thus, the objective of this work was to isolate the effects of the ions over the cells from those caused by the inherent phase transformations in the substituted HA systems. At the same time, to propose a differentiated method for the insertion of these ions into a pre-synthesized HA via ion exchange assisted by microwave radiation. Samples of pure HA and containing the different ions were synthesized by co-precipitation and physic-chemically characterized by wavelength disperse X- ray fluorescence (WDXRF), X-ray diffraction (XRD) with Rietveld refinement and Fourier transform infrared spectroscopy (FTIR), before and after calcination at 1000 °C. Calcined samples were assayed with mouse pre-osteoblastic cells (MC3T3-E1). The samples used in the ion exchange assays were physic-chemically characterized to evaluate the insertion of the elements in the HA lattice. The addition of Mg2+, Mn2+ and Sr2+ ions in the HA lattice, through co-precipitation, promoted the formation of the CaO, MgO and Mn3O4 phases, after calcination at 1000 °C, as well as changes in the unit cell volume. It was observed that Mg2+ ions stimulated the differentiation of the pre-osteoblasts even when segregated from the HA structure as MgO. However, the presence of MgO appeared to retard cell proliferation. At the same time, Mn2+ ions increased cell proliferation and induced the production of high levels of alkaline phosphatase (ALP), regardless whether they were inserted into the HA structure or segregated in the form of Mn3O4. The presence of Sr2+ in the HA lattice did not affect cell behavior, since both proliferation and ALP production were comparable to those observed for pure HA. Regarding the alternative method of ion exchange for inserting the ions into the HA, the microwave radiation heating considerably increased the ion concentration in the HA samples compared to the conventional heating. However, that most of the ions remained in a hydrated layer onto the crystal surface, without significant diffusion to the bulk.