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Articles by Maria Helena Fernandes
Total Records ( 2 ) for Maria Helena Fernandes
  Yuki Shirosaki , Kanji Tsuru , Satoshi Hayakawa , Akiyoshi Osaka , Maria Ascensao Lopes , Jose Domingos Santos , Maria Adelina Costa and Maria Helena Fernandes
  We attempted to prepare chitosan–silicate hybrid for use in a medical application and evaluated the physico-chemical properties and osteocompatibility of the hybrids as a function of γ-glycidoxypropyltrimethoxysilane (GPTMS) concentration. Chitosan–silicate hybrids were synthesized using GPTMS as the reagent for cross-linking of the chitosan chains. Fourier transform infrared spectroscopy, 29Si CP-MAS NMR spectroscopy and the ninhydrin assay were used to analyze the structures of the hybrids, and stress–strain curves were recorded to estimate their Young’s modulus. The swelling ability, contact angle and cytocompatibility of the hybrids were investigated as a function of the GPTMS concentration. A certain fraction of GPTMS in each hybrid was linked at the epoxy group to the amino group of chitosan, which was associated with the change in the methoxysilane group of GPTMS due to hybridization. The cross-linking density was around 80% regardless of the volume of GPTMS. As the content of GPTMS increased, the water uptake decreased and the hydrophilicity of the hybrids increased except when the content exceeded amolar ratio of 1.5, when it caused a decrease. The values of the mechanical parameters assessed indicated that significant stiffening of the hybrids was obtained by the addition of GPTMS. The adhesion and proliferation of the MG63 osteoblast cells cultured on the chitosan–GPTMS hybrid surface were improved compared to those on the chitosan membrane, regardless of the GPTMS concentration. Moreover, human bone marrow osteoblast cells proliferated on the chitosan–GPTMS hybrid surface and formed a fibrillar extracellular matrix with numerous calcium phosphate globular structures, both in the presence and in the absence of dexamethasone. Therefore, the chitosan–GPTMS hybrids are promising candidates for basic materials that can promote bone regeneration because of their controllable composition (chitosan/GPTMS ratio).
  Poliana Lopes , Marcelo Corbellini , Barbara Leite Ferreira , Nuno Almeida , Marcio Fredel , Maria Helena Fernandes and Rui Correia
  A bioactive glass of the 3CaO·P2O5–MgO–SiO2 system was incorporated as a filler into poly(methylmethacrylate)-co-(ethylhexylacrylate) (PMMA-co-EHA) copolymer. The effect of filler proportion (0, 30, 40 and 50 wt.%) on the bending properties was evaluated and a maximum flexural strength of 29 MPa coupled with an elastic modulus of 1.1 GPa was obtained at an intermediate filler concentration (30 wt.%). These values are slightly higher than those usually reported for human cancellous bone. The in vitro bioactivity was assessed by determining the changes in surface morphology and composition after soaking in simulated body fluid (SBF, Kokubo solution). Inductively coupled plasma was used to trace the evolution of ionic concentrations in the SBF solution, namely Ca and P. X-ray diffraction and scanning electron microscopy confirmed the growth of spherical calcium phosphate aggregates on the surface of composites, indicating that the composites are potentially bioactive.
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