Browsing by Author "Sureshbabu, S"

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    Biomimetic deposition of hydroxyapatite on titanium with help of sol-gel grown calcium pyrophosphate prelayer
    (MATERIALS RESEARCH INNOVATIONS, 2011) Sureshbabu, S; Komath, M; Shibli, SMA; Varma, HK
    The biomimetic method is a cost effective, low temperature route for coating hydroxyapatite on titanium bone implants so as to provide an osteointegrating interface. However, biomimetic coatings have the limitations of poor adhesion and lower growth rates. This work investigates the role of a prelayer of calcium pyrophosphate made through sol-gel technique in growing adherent and thick layer of biomimetic hydroxyapatite over titanium surface. Cleaned titanium substrates were dip coated in a calcium-phosphate-citrate sol and calcined at 650 degrees C to form an adherent calcium phosphate layer. These were then subjected to biomimetic processing in 1.5 simulated body fluid for 7-14 days. The prelayer and the biomimetic layer were analysed for micromorphology (using SEM) and chemical phase (using X-ray diffraction, Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy). Thickness measurements were performed on an optical profilometer and the adhesion was assessed through a microcombi scratch tester. The prelayer showed petal-like morphology, whereas globular particles were seen in the biomimetic growth. The prelayer had a thickness of 3.6 mu m and was found to contain calcium pyrophosphate, with calcium titanate at the interface. The phase in the biomimetic layer was identified to be hydroxyapatite, with a growth rate of 5.3 mu m/day. The scratch test gave the delamination load for this layer to be 6.23 N. Results show that it is possible to obtain adherent hydroxyapatite layer on the titanium surface at a faster rate by combining the sol-gel coating and the biomimetic growth technique.
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    In Situ Formation of Hydroxyapatite - Alpha Tricalcium Phosphate Biphasic Ceramics with Higher Strength and Bioactivity
    (JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 2012) Sureshbabu, S; Komath, M; Varma, HK
    Synthetic bone grafts based on hydroxyapatitealpha tricalcium phosphate (HA/a-TCP) biphasic system are preferred for their higher resorbability and bioactivity. In this work, a viable method is suggested to produce HA/a-TCP systems with enhanced bioactivity and mechanical strength, through the in situ conversion of calcium-deficient apatite precursor. A homogeneous precipitation technique was used to produce the precursor powder. It was heat-treated to study the phase conversion using XRD and FTIR. The precursor got converted HA/beta-TCP system above 762 degrees C, which further transformed to HA/a-TCP system after 1165 degrees C. The sintering temperature was optimized at 1175 degrees C. It is the net Ca/P ratio of the precursor which decides the ratio of the phases in the final ceramic. The precursor with Ca/P = 1.585 gave a biphasic ceramic containing 47% a-TCP. The flexural strength of this sample was more than 2.5 times higher compared to the biphasic ceramic made by sintering HA/a-TCP powder mix. The internal microstructure of the ceramic revealed the formation of a-TCP in sheet-like morphology. Preferential dissolution of the a-TCP from the sample surface in aqueous and acidic environment was confirmed quantitatively. Biomimetic growth technique in simulated body fluid has been used to assess the bioactivity in vitro.
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    Nucleation kinetics of the formation of low dimensional calcium sulfate dihydrate crystals in isopropyl alcohol medium
    (CRYSTAL RESEARCH AND TECHNOLOGY, 2012) Sandhya, S; Sureshbabu, S; Varma, HK; Komath, M
    Calcium sulfate dihydrate, constituted as uniform crystals of low dimensions, is a potential biomaterial for clinical applications like bone graft substitution and drug delivery. In this work, isopropyl alcohol has been used as a solvent to obtain low dimensional calcium sulfate dihydrate crystals from calcium nitrate - sulfuric acid system. Reactants in 0.5 molar concentration at ambient conditions generated uniform rod-shaped crystals of length 35 mu m. Analysis using X-ray Diffractometry and Fourier Transform Infrared Spectrometry showed the material to be well crystallized, phase-pure calcium sulfate dihydrate. The nucleation kinetics has been studied by observing the induction time of phase formation in solutions of millimolar concentrations through turbidimetry at 300 K. The data have been analysed using classical nucleation theory to deduce parameters like interfacial tension (or surface free energy), nucleation rate and critical radius. The surface free energy obtained (5.6 mJ/m2) is comparatively lower than that reported for aqueous precipitation, which could be attributed to the presence of isopropyl alcohol. On escalating the supersaturation ratio, the nucleation rate drastically increased and the critical radius decreased exponentially. Particles formed at supersaturation 1.39 showed a monomodal distribution centered at 8.2 nm in Dynamic Light Scattering analysis. Comparable particle sizes were obtained in Transmission Electron Microscopy.
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    Oriented growth of surface grains in sintered beta tricalcium phosphate bioceramics
    (MATERIALS LETTERS, 2001) Varma, HK; Sureshbabu, S
    Preferential orientation of sintered surface grains of beta tricalcium phosphate (P TCP) ceramic was studied by X-ray diffraction (XRD) method and scanning electron microcopy (SEM). The P TCP powder was prepared by calcining the precipitate at 800 degreesC, obtained by precipitation method involving calcium nitrate and ammonium dihydrogen orthophosphate. The powder was compacted and sintered at 1150 degreesC to similar to 95% density. The surface grains of the above ceramic were found to preferentially orient with respect to a-b plane by XRD study. High grain growth was observed to the surface grains compared to the bulk grains. (C) 2001 Elsevier Science B.V. All rights reserved.
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    Preparation and analysis of chemically gradient functional bioceramic coating formed by pulsed laser deposition
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 2012)
    Bioactive ceramic coatings based on calcium phosphates yield better functionality in the human body for a variety of metallic implant devices including orthopaedic and dental prostheses. In the present study chemically and hence functionally gradient bioceramic coating was obtained by pulsed laser deposition method. Calcium phosphate bioactive ceramic coatings based on hydroxyapatite (HA) and tricalcium phosphate (TCP) were deposited over titanium substrate to produce gradation in physico-chemical characteristics and in vitro dissolution behaviour. Sintered targets of HA and alpha-TCP were deposited in a multi target laser deposition system. The obtained deposits were characterized by X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis. Inductively coupled plasma spectroscopy was used to estimate the in vitro dissolution behaviour of coatings. The variation in mechanical property of the gradient layer was evaluated through scratch test and micro-indentation hardness. The bioactivity was examined in vitro with respect to the ability of HA layer to form on the surface as a result of contact with simulated body fluid. It could be inferred that chemically gradient functional bioceramic coating can be produced by laser deposition of multiple sintered targets with variable chemical composition.