Produção acadêmica-PPGPM

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https://repositorio.univap.br/handle/123456789/98

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Navegando Produção acadêmica-PPGPM por Autor "Borges, João Paulo"

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    Piezoelectric calcium modified barium titanate for bone regeneration
    Madeira, Ricardo M. D.; Vieira, Tânia; Silva, Jorge Carvalho; Oliveira, Ivone Regina de; Borges, João Paulo; Lima, Maria Margarida Rolim Augusto; Lança, Maria Carmo; Marinha Grande, Portugal
    Solid state reaction was used to produced barium titanate modified with calcium (BCT) showing the presence of the piezoelectric tetragonal phase after sintering at 1350 ◦C. Bioglass 45S5 (BG) was synthetized by sol-gel route. From these two materials and commercial hydroxyapatite (HAp) were obtained composites. The BG produced showed some cytotoxic character that was weakened by passivation. All other materials were non-cytotoxic. Contact polarization at constant temperature was chosen composites polarization. Electric/dielectric properties were evaluated by thermally stimulated depolarization currents (TSDC). The material showed bioactivity with the composite with BCT/BG/HAp 90/5/5 (wt%) showing increased bioactivity. In vitro test showed high proliferation rates for the composites.
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    Properties of strontium-containing BG 58S produced by alkali-mediated sol-gel process
    (Elsevier) Oliveira, Ivone Regina de; Barbosa, Ana Maria; Santos, Kennedy Wallace dos; Lança, Maria Carmo; Lima, Maria Margarida Rolim Augusto; Vieira, Tânia; Silva, Jorge Carvalho; Borges, João Paulo
    Among many bioglass (BG) compositions, gel-BG 58S has been indicated in the literature for applications as bone graft due to its promising use to repair bone defects. However, its physical and biological properties also depend of choice of precursors. The use of phosphoric acid as a source of P2O5 changes the thermal behavior of BG and in the presence of HNO3 increases the rate of hydrolysis and reduces the size of sol particles, thus influencing the surface area and in turn rate of apatite formation of bioactive glasses. In addition, the addition of concentrated NH4OH decreases the gelation time and new bioactive materials have been produced using Ca/Sr substitution in BG compositions. Thus, the aim of this work was to prepare BG 58S by the sol-gel technique at room temperature using phosphoric acid (PA) as the phosphorus precursor compared with conventional precursor triethylphosphate (TEP) and to evaluate the effect of the adding NH4OH (1 or 2 M) as gelation catalyst in order to select the better route to Sr incorporate. The products were characterized using XRD, FTIR and confocal Raman spectroscopy. The composition prepared with 1M NH4OH (PA-1M) presented more evidence of NBO bonds, and the absence of crystallinity. Thus, BG 58S-5 wt% Sr was prepared using the alkali-mediated sol-gel process (PA-1M) and characterized as the techniques mentioned in addition to bioactivity and cytotoxicity assays. Both compositions showed the development of a layer of apatite when treated in a simulated body fluid (SBF). Strontium composition showed higher cell viability and more evidence of calcium phosphate formation while calcium carbonate is mainly identified in strontium-free composition.