Browsing by Author "Espinosa, FF"

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    In-vitro calcium phosphate growth over functionalized cotton fibers
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 1999) Varma, HK; Yokogawa, Y; Espinosa, FF; Kawamoto, Y; Nishizawa, K; Nagata, F; Kameyama, T
    Biomimetic growth of calcium phosphate compound on cotton sheets treated with tetraethoxy silane and soaked in simulated body fluid solution was studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), micro-Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). Micro-FTIR and EDAX results show that silicon was coupled to the cotton fiber when cotton was treated with tetra-ethoxy silane (TEOS) at 125 degrees C for 1 h. Calcium phosphate nucleation started to occur on the surface of TEOS-treated cotton fibers upon immersion in 1.5 x SBF (simulated body fluid solution) within 3 days and after 20 days, all the fiber surfaces were found covered with a thick and porous coating of calcium phosphate. The Ca and P determined by inductively coupled plasma spectroscopy (ICP) analysis revealed that the Ca/P ratio as well as the amount of calcium phosphate coating depends on the soaking time in SBF solution. (C) 1999 Kluwer Academic Publishers.
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    Porous calcium phosphate coating over phosphorylated chitosan film by a biomimetic method
    (BIOMATERIALS, 1999) Varma, HK; Yokogawa, Y; Espinosa, FF; Kawamoto, Y; Nishizawa, K; Nagata, F; Kameyama, T
    A porous calcium phosphate coating deposited on chitosan films was studied using scanning electron microscopy, energy-dispersive X-ray analysis, micro-Fourier transform infrared spectroscopy (micro-FTIR) and thin-film X-ray diffractometry (XRD). Chitosan films were first prepared by dissolving chitosan powder in dilute acetic acid and drying in a hat petri dish. The films were phosphorylated using urea and H3PO4 with the P content being 0.1-0.2 wt%. Phosphorylated films soaked in saturated Ca(OH)(2) solution for 8 days led to the formation of a calcium phosphate precursor phase over the entire surface. This precursor phase stimulated the growth of a porous coating of calcium-deficient hydroxy apatite when immersed in 1.5 x SBF for mon than 20 days. Phosphorylated films not treated with Ca(OH)(2) did not show any calcium phosphate growth upon immersion in SBF solution. The precursor phase is thought to be octacalcium phosphate, which nucleates a HAP phase during SBF treatment. Initially, this treatment in SBF results in the formation of a single-layer calcium phosphate particles over the film surface. As immersion time in SBF increases, further nucleation and growth produce a porous HAP coating. The Ca/P ratio of the HAP coating is a function of SBF immersion time. (C) 1999 Elsevier Science Ltd. All rights reserved.