M.C.F. Magalhães
University of Aveiro
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Featured researches published by M.C.F. Magalhães.
Journal of Materials Science: Materials in Medicine | 1996
Rui N. Correia; M.C.F. Magalhães; Paula A. A. P. Marques; A.M.R. Senos
Hydroxyapatite powders with reproducibly different Ca/P ratios and powders with varying amounts of co-precipitated magnesium, sodium and potassium were synthesized by a wet method. Solids composition, particle size and morphology, crystalline structure, sintering behaviour and microstructure were investigated in order to understand the effect of composition in the properties of the powders. Under the present conditions of synthesis, it was concluded that magnesium, sodium and potassium will enter the hydroxyapatite lattice in vestigial amounts. Magnesium gives rise to a co-precipitated amorphous phase which crystallizes as β-whitlockite on calcining. A relationship was found between the Ca/P ratio in hydroxyapatite and its sinterability. The sintering process of pure and alkali-containing hydroxyapatites is completed at 1300 °C and leads to dense ceramics in the case of pure and sodium-containing hydroxyapatites but not in potassium-containing material.
Biomaterials | 2003
Paula A. A. P. Marques; M.C.F. Magalhães; Rui N. Correia
The substitution of tris/HCl buffer by CO(2)/HCO(3)(-) buffer in inorganic plasma was studied. An appropriate gas mixture of CO(2)/N(2) was continuously bubbled in Kokubos SBF solution prepared without addition of Tris/HCl. This method enables buffering the solution within the 7.3-7.4 pH interval and, at the same time, reaching a HCO(3)(-) concentration between 24 and 27 mmol dm(-3), which are the normal concentrations reported for blood plasma. Mineralisation studies on calcium phosphate ceramics using this solution showed that, in the presence of such hydrogencarbonate concentrations, the formation of a mineralisation layer on the ceramic occurs via a carbonated octacalcium phosphate, that evolves to carbonated hydroxyapatite. The results suggest that mineralisation studies in this new carbonate-containing simulated inorganic plasma mimic biomineralisation more closely than traditional SBF.
Biomaterials | 2003
Paula A. A. P. Marques; Ana Paula Serro; Benilde Saramago; Anabela C. Fernandes; M.C.F. Magalhães; Rui N. Correia
The role of albumin in the mineralisation process of commercial hydroxyapatite (HAp) and synthesised biphasic (HAp-tricalcium phosphate) ceramics in a bufferless simulated inorganic plasma (HBSS) was investigated by conventional in vitro tests and static and dynamic wettability measurements. Albumin was either pre-adsorbed or solubilised in HBSS. It was found that calcium complexation by albumin plays a key role in early mineralisation kinetics, so that mineralisation is favoured when albumin is pre-adsorbed and hindered when it is dissolved in HBSS. In the biphasic ceramic this picture is complicated by the fact that albumin, in solution, seems to promote the dissolution of tricalcium phosphate, and simultaneously compete for calcium with the ceramic. It also appears that albumin has a stabilising effect of octacalcium phosphate present in deposits on commercial HAp. The same effect may be present in the case of the biphasic ceramic, at earlier mineralisation times, when octacalcium phosphate appears as a precursor of HAp. Octacalcium phosphate formation on commercial apatite is accompanied by carbonate substitution in phosphate positions.
Journal of Materials Chemistry | 2003
Paula A. A. P. Marques; Ana Paula Serro; Benilde Saramago; Anabela C. Fernandes; M.C.F. Magalhães; Rui N. Correia
Two ceramic phosphates, commercial hydroxyapatite and synthesised biphasic hydroxyapatite–14 wt.% α-tricalcium phosphate, were incubated in Hanks balanced salt solution (HBSS) and Kokubos simulated body fluid (SBF) at 37 °C and the respective surface modifications investigated. The static contact angles (SCA) of water and diiodomethane on the surfaces of both incubated and non-incubated materials were measured as a function of time, showing that surface modifications were different for each type of phosphate and depended on the incubating solution. Dynamic contact angle (DCA) hysteresis provided information on the characteristics of possible deposits. These studies were complemented with SEM/EDS, FTIR and XRD analysis of the surfaces. Compositional changes in the incubating solutions with time were monitored by ICP spectroscopy. The main conclusions are (1) the presence of α-tricalcium phosphate in the synthesised biphasic hydroxyapatite enhances the deposition of calcium phosphate, (2) the precipitation of calcium phosphate is favoured by the pH increase of the incubating solution; consequently, buffer Tris inhibits the deposition because it avoids the pH increase and forms soluble complexes with Ca2+ ions. Another conclusion is that wettability measurements, especially DCA, provide a most sensitive method to detect surface transformations leading to mineralisation.
Journal of Materials Chemistry | 2004
Paula A. A. P. Marques; Sandra C.P. Cachinho; M.C.F. Magalhães; Rui N. Correia; Maria Helena F.V. Fernandes
A carbonated simulated inorganic plasma (CSIP) physiologically buffered with carbonate-hydrogencarbonate, where a flow of CO2 at controlled partial pressure enables pH control between 7.3–7.4 while maintaining a constant HCO−3 concentration within the plasmatic range (24 to 27 mmol dm−3), was previously developed and reported by the authors. The present work represents a step forward, by introducing albumin in this solution, to produce albumin-containing CSIP (CSIPA). Mineralisation studies were performed on three materials (two calcium phosphate ceramics and a glass of the Si-Ca-Mg-P system) in CSIPA, and compared with those performed in traditional Tris-buffered Kokubos SBF containing albumin (SBFA). It was found that the formation of apatite deposits in CSIPA is favoured when compared not only with SBFA, but also with albumin-free CSIP. The results indicate that the presence of HCO−3 in physiological concentration and/or the absence of Tris/HCl buffer may alter the role of albumin in the mineralising medium. The results also suggest that CSIPA-simulated plasma not only mimics in vivo biomineralisation more closely than traditional SBF, but may also be a suitable medium for biomimetic deposition of apatite.
Journal of Solution Chemistry | 1999
Heinz Gamsjäger; Wolfgang Preis; E. Königsberger; M.C.F. Magalhães; Paula Brandão
AbstractThe solubilities of CdCO3 (otavite) in aqueous NaClO4 solutions have been investigated as a function of ionic strength (0.15 ≤ I/mol-kg−1 ≤ 5.35, 25°C) and temperature (25°C ≤ T ≤ 75°C, I = 1.00 mol-kg−1). A new Chemsage optimization routine was employed to simultaneously evaluate solubility data from this work and other sources, as well as standard electrode potentials determined at different ionic strengths. With the Pitzer equations the solubility constants,
Materials Science Forum | 2008
B.J.M. Leite Ferreira; M.C.F. Magalhães; Rui N. Correia
Assessment, Restoration and Reclamation of Mining Influenced Soils | 2017
Erika S. Santos; Maria Manuela Abreu; M.C.F. Magalhães
{}^*K_{{\text{ps0}}}^{\text{I}}
Journal of Physical and Chemical Reference Data | 2011
Heinz Gamsjäger; M.C.F. Magalhães; E. Königsberger; K. Sawada; B. R. Churagulov; P. Schmidt; D. Zeng
Key Engineering Materials | 2003
Paula A. A. P. Marques; M.C.F. Magalhães; Rui N. Correia; Ana Isabel Martín; Antonio J. Salinas; María Vallet-Regí
, were extrapolated to infinite dilution resulting in log