Browsing by Author "Sunny, MC"

Now showing 1 - 13 of 13
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    A comparative evaluation of coefficient of friction and mechanical properties of commercially available foley catheters
    (JOURNAL OF BIOMATERIALS APPLICATIONS, 2001)
    Three commercially available urinary catheters were evaluated for their coefficient of friction and mechanical properties, which are two important parameters as far as the intended use is considered. The apparent coefficient of friction was measured from the slope of the force versus normal load graph using an in-house fabricated setup. The mechanical properties like ultimate tensile strength, elongation at break and modulus were evaluated before and after aging in synthetic urine. The swelling behavior of the catheter samples was studied in toluene and found to correlate well with the mechanical properties.
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    Effect of partial replacement of di(2-ethyl hexyl)phthalate, by a polymeric plasticizer, on the permeability and leaching properties of poly(vinyl chloride)
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2006) Sunny, MC; Ramesh, P; George, KE
    Acrylonitrile butadiene rubber (NBR) was used as a polymeric plasticizer in poly(vinyl chloride) (PVC) for the partial replacement of di(2-ethyl hexyl)phthalate (DEHP). The effect of this partial replacement on DEHP leaching from the PVC was evaluated at 10, 25, and 40 degrees C. The study shows that the incorporation of NBR reduces the rate of DEHP leaching, the reduction being prominent at lower temperatures. Gas permeability of the NBR-modified samples was also evaluated at the above temperatures using oxygen and carbon dioxide. A reduction in gas permeability is observed in NBR-modified samples compared to the PVC plasticized with DEHP alone particularly in the case of carbon dioxide. Water vapor transmission rates of the NBR-modified samples are higher than that of the control sample. The NBR-modified PVC sample was found to be noncytotoxic in the in vitro cytotoxic evaluation both by direct contact and test on extract methods. (c) 2006 Wiley Periodicals, Inc.
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    Extrusion of hydroxyapatite to clinically significant shapes
    (MATERIALS LETTERS, 2000) Velayudhan, S; Ramesh, P; Sunny, MC; Varma, HK
    Synthetic hydroxyapatite (HAP) particles were incorporated into ethylene vinyl acetate (EVA) co-polymer and then shaped into various forms by simple plastic-forming techniques. Composites with HAP volume of fraction from 10-60% were prepared and shaped. The shapes thus formed were subjected to thermal debinding and subsequent sintering to 1150 degreesC. Retention of shapes was found after thermal debinding and sintering of composites above 30 vol.% of HAP. (C) 2000 Elsevier Science B.V. All rights reserved.
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    Hydroxyapatite filled chitosan-polyacrylic acid polyelectrolyte complexes
    (JOURNAL OF MATERIALS SCIENCE, 2003) Sailaja, GS; Velayudhan, S; Sunny, MC; Sreenivasan, K; Varma, HK; Ramesh, P
    Chitosan (CHI) has been complexed with polyacrylic acid (PAA) in the presence of hydroxyapatite (HAP) to prepare composites intended for bone substitute applications. Thermogravimetric analysis of the composite showed that the presence of HAP had little effect on the degradation profile of the polyelectrolyte complex (PEC), except for the onset of degradation. Optimum compressive strength was observed for 70-weight percentage HAP filled PEC. The morphological analysis revealed that the HAP particles were uniformly distributed in the PEC matrix. The results indicate that HAP filled PEC of CHI and PAA could be prepared following the proposed simple route. (C) 2003 Kluwer Academic Publishers.
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    Inherently X-ray opaque polyurethane microspheres for biomedical applications
    (INTERNATIONAL JOURNAL OF POLYMERIC MATERIALS AND POLYMERIC BIOMATERIALS, 2017) Kiran, S; Sunny, MC; Joseph, R
    In this work synthesis and characterization of inherently X-ray opaque, nonresorbable polyurethane microspheres with well-calibrated particles in a defined range of sizes suitable for embolization is reported. In order to impart X-ray opacity to the polyurethane, a bifunctional monomer, namely, 4,4-isopropylidenediphenol (BPA) was iodinated and this iodinated compound was used as one of the monomers during polyurethane synthesis. The resultant X-ray opaque polyurethane was converted into microspheres using an oil-in-water emulsion and solvent evaporation technique. Microspheres obtained had diameters in the range of 200-500 mu m, were noncytotoxic and free from X-ray attenuating additives. In vivo X-ray fluoroscopic imaging carried out in a rabbit cadaver model showed that these microspheres were sufficiently X-ray opaque to be visualized under fluoroscopic conditions. [GRAPHICS] .
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    Metallocene based polyolefin: a potential candidate for the replacement of flexible poly (vinyl chloride) in the medical field
    (POLYMERS FOR ADVANCED TECHNOLOGIES, 2010) Sunny, MC; Ramesh, P; Mohanan, PV; George, KE
    A comparative assessment of the performance properties of metallocene polyolefin (m-PO) with those of plasticized poly (vinyl chloride) (pPVC) and ethylene vinyl acetate (EVA) copolymer having 18% vinyl acetate content (EVA-18), the two common polymers used for flexible medical products, is carried out. The preliminary evaluation of the processability, mechanical properties, and thermal stability of the new material, m-PO is described. The processability parameters like mixing torque and melt viscosity of m-PO are found to be comparable with those of pPVC and EVA-18. Mechanical properties such as tensile strength, elongation at break, and tear strength (TS) of m-PO are much higher than that of pPVC and EVA-18. Thermo gravimetric analysis (TGA) indicates that the thermal degradation of m-PO takes place only at temperatures above 340 degrees C and can be processed at 170 degrees C without much damage. Oxygen and carbon dioxide permeabilities of m-PO at three different temperatures (10, 25, and 40 degrees C) are evaluated and compared with those of pPVC and EVA-18. It could be seen that the permeabilities of both the gases for m-PO at three temperatures were lower than those of pPVC and EVA. Biological evaluation of m-PO is carried out by assessing its cytotoxicity, hemolytic property, and blood clotting initiation. The cytotoxicity studies indicate that m-PO is non-toxic to the monolayer of L929 mammalian fibroblast cell lines on direct contact or the exposure of its extract. Non-hemolytic property of m-PO by direct contact as well as test on extract is revealed both in static and in dynamic conditions. Blood clotting time experiments indicate that the initiation of blood clotting due to m-PO is faster than that of pPVC and EVA-18. Copyright (C) 2009 John Wiley & Sons, Ltd.
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    Microstructured microspheres of hydroxyapatite bioceramic
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 2002)
    Hydroxyapatite (HAP) particles having spherical geometry and 125-1000 mum in size range were prepared using a solid-in-water-in-oil (S/W/O) emulsion, cross-linking technique. An aqueous solution of chitosan containing different loading of HAP was dispersed as droplet in liquid paraffin using a stabilizing agent. Cross-linking of chitosan was induced by adding appropriate amount of glutaraldehyde saturated toluene. Chitosan microspheres containing HAP were sintered at 1150 degreesC to obtain pure HAP microspheres. The spheres thus produced were examined by scanning electron microscopy. The percentage yield and size distributions of the spheres were also determined. (C) 2002 KLuwer Academic Publishers.
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    Phase transfer catalysed surface modification of plasticized poly(vinyl chloride) in aqueous media to retard plasticizer migration
    (POLYMER, 1996) Jayakrishnan, A; Sunny, MC
    Plasticized poly(vinyl chloride) (PVC) sheets were surface modified by nucleophilic substitution of chlorine by azide in aqueous media under phase transfer conditions. PVC was reacted with a 40% solution of sodium azide in water using tetrabutyl ammonium bromide as the phase transfer catalyst. The reaction was conducted at temperatures ranging from 50 to 80 degrees C for various periods of time (1-4 h). The azidated PVC surface was then irradiated using u.v. light with a 125W lamp for various time periods to crosslink the surface. Migration of the plasticizer di-(2-ethylhexyl phthalate) from surface modified and unmodified PVC was examined in a potential organic extractant such as hexane. It was found that considerable reduction in the migration of the plasticizer could be achieved by this technique depending on the extent of azidation of the PVC surface and the irradiation dose. Determination of the stress/strain properties of PVC sheets before and after modification showed that there was around 30% reduction in these properties after surface modification. However, the values were still much above the minimum prescribed for vinyl chloride polymers used in biomedical applications. Copyright (C) 1996 Elsevier Science Ltd.
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    Poly (L-lactide-co-epsilon caprolactone) microspheres laden with bioactive glass-ceramic and alendronate sodium as bone regenerative scaffolds
    (MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 2012) Mondal, T; Sunny, MC; Khastgir, D; Varma, HK; Ramesh, P
    Microspheric scaffolds of poly-(lactide-co-caprolactone) loaded with alendronate sodium, a family precursor of bisphosphonate drug and bioactive glass-ceramic (BGS) were prepared for the treatment of osteoporosis like bone defects with the rationale of getting a combined effect/concurrent advantage of osteoclast apoptosis as well as the augmentation of bone regeneration. The porous microspheres were generated by oil in water/solvent evaporation technique. The distribution of bioactive glass-ceramic was evidenced by the microcomputed tomography (mu-CT) and scanning electron microscopy analyses. The microspheres were evaluated for their in vitro cytocompatibility using L929 cell line and were found to be noncytotoxic. The osteoinductivity of the scaffold was assessed by its response in simulated body fluid and observed an excellent hydroxy carbonate apatite (HCA) layer formation on the surface which revealed the bone bonding and bone regeneration capability of the scaffold. The cell adhesion studies was performed with L-929 cell line and a marking cell growth on the surface as well as in the pores of the bioactive glass-ceramic as well as bioactive glass-ceramic cum drug incorporated microspheres was evidenced by the Confocal laser scanning microscopy (CLSM) investigation. No cell adhesion was observed onto the surface of the bare microspheres prepared by the copolymer alone where as the bioactive glass-ceramic and drug cum bioactive glass-ceramic loaded microspheres were found to promote the cell adhesion. The viability of the adhered cells on the microspheres was checked by flourescein diacetate (FDA) staining and it was observed that the adhered cells were viable and metabolically active. The release of the drug, alendronate sodium, directly into the problem site makes the presently prepared microsphere superior to the oral variety of drug available which is associated with oral discomfort and low bioavailability. (c) 2012 Elsevier B.V. All rights reserved.
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    Porous composites of hydroxyapatite-filled poly[ethylene-co-(vinyl acetate)] for tissue engineering
    (POLYMER INTERNATIONAL, 2011) Sunny, MC; Vincy, PV; Kumar, PRA; Ramesh, P
    A novel porous composite of hydroxyapatite/poly[ethylene-co-vinyl acetate)] (HAP/EVA) having better osteointegration was fabricated by gas foaming technique using a non toxic gas blowing agent intended for bone replacement applications. Combined techniques of scanning electronic microscopy (SEM) and X-ray microcomputed tomography (mu CT) analysis showed that the pore size and pore volume of the porous composite decrease with the increase of HAP content. The gravimetric analysis evidenced for good pore interconnectivity within the porous composites. Energy dispersive X-ray analysis (EDX) studies inveterated the even scattering of Ca ions which in turn indicate the uniform dispersion of HAP particles in the composites. The significant gradation in Ca ion concentration seen in EDX studies is well accordance with the amount of HAP loading in the sample. Mechanical properties of the porous composite having different HAP content were measured to have the compressive strength varying from 1.06 to 2.2 MPa. Non-cytotoxic character of the material was observed by the cytocompatibility studies. The metabolic activity of L929 cells seeded on the material assessed by [3-(4,5-dimethylthiazol)-2-yl]-2,5-diphenyltertrazolium bromide (MTT) assay was found to be 91.8%. The adhesion and migration of the cells inside the pore walls were visualized by confocal microscopy. (C) 2010 Society of Chemical Industry
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    Preparation of microstructured hydroxyapatite microspheres using oil in water emulsions
    (BULLETIN OF MATERIALS SCIENCE, 2005) Pradeesh, TS; Sunny, MC; Varma, HK; Ramesh, P
    Hydroxyapatite (HAP) microspheres with peculiar spheres-in-sphere morphology were prepared by using oil-in-water emulsions and solvent evaporation technique. Ethylene vinyl acetate co-polymer (EVA) was used as the binder material. Preparation of HAP/EVA microspheres was followed by the thermal debinding and sintering at 1150 degrees C for 3 h to obtain HAP microspheres. Each microsphere of 100-1000 mu m was in turn composed of spherical hydroxyapatite granules of 2-15 mu m size which were obtained by spray drying the precipitated HAP. The parameters such as percentage of initial HAP loading, type of stabilizer, concentration of stabilizer, stirring speed and temperature of microsphere preparation were varied to study their effect on the particle size and geometry of the microspheres obtained. It was observed that these parameters do have an effect on the size and shape of the microspheres obtained, which in turn will affect the sintered HAP microstructure. Of the three stabilizers used viz. polyoxyethylene(20) sorbitan monopalmitate (Tween-40), sodium laurate and polyvinyl alcohol (PVA), only PVA with a concentration not less than 0.1 wt% showed controlled stabilization of HAP granules resulting in spherical microspheres of required size. Morphologically better spherical microspheres were obtained at 20 degrees C. Increasing the stirring speed produced smaller microspheres. Smaller microspheres having size < 50 mu m were obtained at a stirring speed of 1500 +/- 50 rpm. A gradual decrease in pore size was observed in the sintered microspheres with increase in HAP loading.
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    Use of 2-hydroxyethyl methacrylate as a solidifying monomer in balloon embolization is a dangerous affair
    (PROCEEDING OF THE FIRST REGIONAL CONFERENCE - IEEE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY AND 14TH CONFERENCE OF THE BIOMEDICAL ENGINEERING SOCIETY OF INDIA, 1995) Jayakrishnan, A; Thanoo, BC; Sunny, MC
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    Use of polymeric plasticizers in polyvinyl chloride to reduce conventional plasticizer migration for critical applications
    (JOURNAL OF ELASTOMERS AND PLASTICS, 2004) Sunny, MC; Ramesh, P; George, KE
    Di-(2-ethyl hexyl) plithalate (DEHP), a conventional plasticizer in polyvinyl chloride (PVC), was partially replaced by polymeric plasticizers. Three different elastomers such as nitrile rubber (NBR), carboxylated nitrile rubber (XNBR) and epoxidized natural rubber (ENR) were used as polymeric plasticizers. Mechanical properties and leaching of DEHP of the modified PVC in comparison to the compound containing DEHP alone were investigated. The study shows that the migration of the DEHP can be reduced significantly without affecting the useful mechanical properties.