Browsing by Author "Yokogawa, Y"
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Item Biomimetic growth of calcium phosphate over ATP coupled PMMA films(BIOCERAMICS 15, 2003) Yokogawa, Y; Varman, HK; Sreenivasan, KBiomimetic growth of calcium phosphate phase was studied over phosphate group functionalised polymethy methaerylate (PMMA) films using Fourier Transform Infrared Spectroscopy (FTIR), Electron Spectroscopy (ESCA), Scanning Electron Microscopy (SEM) and Energy Dispersive X ray Analysis(EDS). PMMA films were prepared by dissolving PMMA pellets in chloroform and cast into thin sheets. The films were immersed in a methanol solution of sodium hydroxide before treating with 1.5% solution of adenosine triphosphate (ATP) at a pH of 5.2 for 24 hours. The films were then soaked in saturated lime solution for 4 days to initiate formation of calcium phosphate precursor phase over their surface. The above films immersed in simulated body fluid solution (1.5 x SBF) for more than 5 days led to the nucleation of apatitic calcium phosphate phase over the film surface.Item In vitro calcium phosphate growth over surface modified PMMA film(BIOMATERIALS, 2003)In vitro nucleation of calcium phosphate phase was studied over functionalized polymethyl methacrylate (PMMA) films using Fourier transform infrared spectroscopy, electron spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis. PMMA films were prepared by dissolving commercial grade pellets in chloroform and cast into thin sheets. The films were immersed in a methanol solution of sodium hydroxide before treating with 1.5% solution of adenosine triphosphate (ATP) at a pH of 5.2 for 24 h. ATP treated films were then soaked in saturated lime solution for 4 days to initiate formation of calcium phosphate precursor phase over their surface. The above films immersed in simulated body fluid solution (1.5 x SBF) for more than 5 days led to the nucleation of apatitic calcium phosphate phase all over the film surface. The ATP coupled film not subjected to lime treatment did not show calcium phosphate nucleation behaviour upon immersion in SBF solution. The Ca/P ratio of the calcium phosphate phase increase with increase in soaking time in SBF solution. (C) 2002 Elsevier Science Ltd. All rights reserved.Item In vitro mineralization and cell adhesion on surface modified poly (2-hydroxy ethyl methacrylate-co-methyl methacrylate)(BIOCERAMICS 18, PTS 1 AND 2, 2006) Sailaja, GS; Kumari, TV; Yokogawa, Y; Varma, HKPoly(2-hydroxyethyl methacrylate-co- methyl methacrylate) HM, was synthesized by free radical copolymerization, cross-linked with ethylene glycol dimethacrylate and phosphorylated. The phosphate coupling was ensured by ATR spectroscopy. The in vitro mineralization ability of the phosphorylated HM (designated as PHM) was investigated by studying the nucleation and growth of calcium phosphate on its surface by immersing in simulated body fluid (SBF) solution. The coating morphology was studied by SEM and the Ca/P ratio of the coating by EDX analysis. The cell adhesion behaviour of PHM was studied by seeding Human osteosarcoma (HOS) cells for one week followed by SEM analysis along with HM as control. It was observed that HOS cells exhibited biomineralization of calcium phosphate on the surface of HM as well as on PHM with a significantly higher amount on the surface of PHM as observed by von kossa staining method. The results show that PHM is capable of in vitro mineralization under simulated physiological condition, promotes cell adhesion by providing an excellent cell friendly surface and it exhibits biomineralization of calcium phosphate in presence of HOS cells.Item 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, TBiomimetic 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.Item 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, TA 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.Item Pulsed laser deposition of hydroxyapatite on nanostructured titanium towards drug eluting implants(Materials Science and Engineering: C. 2013, 2013-04) Rajesh, P; Mohan, N; Yokogawa, Y; Varma, HKItem Synthesis and Characterization of Iron Oxide Embedded Hydroxyapatite Bioceramics(JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 2012) Ansar, EB; Ajeesh, M; Yokogawa, Y; Wunderlich, W; Varma, HA homogeneous dispersion of nano iron oxide (IO) crystallites inside the hydroxyapatite (HA) particles was achieved by a co-precipitation method. This highly stable colloidal dispersion of magnetic nano composite (HAIO) was made without the use of any surfactants. The in situ generated dispersion of the composite powders showed submicron HA particles with 5 nm iron oxide inside. The phase analysis results showed the presence of hydroxyapatite (HA) and iron oxide with no tertiary phase. The enhancement of relative peak intensities with increased percentage of iron oxide phase in X-ray diffraction analysis suggests the formation of iron oxide together with HA without affecting the phase purity of the latter, which is important when the biological behavior of HA is concerned. This also confirms the quantitative nature of the precipitated nanocomposites. The High Resolution Transmission Electron Microscope (HRTEM) of the composite shows elongated crystal flakes or platelike surfaces of HA crystallites having particle sizes in the range 70-100 nm. HRTEM with XRD analysis matches HAIO only with iron oxide particles of Magnetite (Fe3O4) and HA phases. The FTIR data confirm that the introduction of iron oxide did not produce any considerable change in the chemical structure of HA.