Browsing by Author "Ramesh, P"

Now showing 1 - 20 of 46
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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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    Assessment of in vivo chromosomal aberrations - Potency of zinc mercapto benzo thiazole
    (JOURNAL OF BIOMATERIALS APPLICATIONS, 2000)
    Chromosomal aberrations are microscopically visible changes in the chromosome structure. The double-stranded breaks are the ultimate DNA lesions for chromosomal aberrations. The purpose of the present study was to evaluate the induction of chromosomal aberrations by the rubber accelerator zinc mercapto benzo thiazole (ZMBT). The experiment was designed with five groups, each composed of four Swiss albino mice. The first three groups received ZMBT at 1920, 960, and 483 mu g/20 g animal. The remaining two groups were the vehicle (cotton seed oil) and positive (methyl methane sulphonate) controls. Animals were given a single dose of test; and control samples by IP injection. Colchicine (20 mu g/animal) was administered 90 minutes before sacrificing the animals. All the animals were sacrificed at the end of 36 h by cervical dislocation. Bone marrow preparations were made, stained with Giemsa stain, and examined for chromosomal abnormalities. The results indicated a lack of incidence of chromosomal abnormalities in the test and control groups. However, significant chromosomal abnormalities such as gaps, breaks, and translocations were observed in the positive control group. Hence, the study concluded that ZMBT at different concentrations fails to induce structural chromosomal aberrations in bone marrow cells.
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    Biomimetic approaches with smart interfaces for bone regeneration
    (JOURNAL OF BIOMEDICAL SCIENCE, 2016) Sailaja, GS; Ramesh, P; Vellappally, S; Anil, S; Varma, HK
    A 'smart tissue interface' is a host tissue-biomaterial interface capable of triggering favourable biochemical events inspired by stimuli responsive mechanisms. In other words, biomaterial surface is instrumental in dictating the interface functionality. This review aims to investigate the fundamental and favourable requirements of a 'smart tissue interface' that can positively influence the degree of healing and promote bone tissue regeneration. A biomaterial surface when interacts synergistically with the dynamic extracellular matrix, the healing process become accelerated through development of a smart interface. The interface functionality relies equally on bound functional groups and conjugated molecules belonging to the biomaterial and the biological milieu it interacts with. The essential conditions for such a special biomimetic environment are discussed. We highlight the impending prospects of smart interfaces and trying to relate the design approaches as well as critical factors that determine species-specific functionality with special reference to bone tissue regeneration.
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    Blends of thermoplastic polyurethane (TPU) and polydimethyl siloxane rubber (PDMS), part-I: assessment of compatibility from torque rheometry and mechanical properties
    (JOURNAL OF POLYMER RESEARCH, 2012) Rajan, KP; Al-Ghamdi, A; Ramesh, P; Nando, GB
    Thermoplastic polyurethane (TPU) and polydimethyl siloxane rubber (PDMS) are two major polymers used extensively for biomedical applications. Blending of these polymers combines the superior mechanical properties, abrasion resistance, solvent resistance and aging resistance of TPU with chemical stability, inertness, flexibility and biocompatibility of PDMS. In the present investigation, an 80: 20 blend of TPU and PDMS was selected for the preparation of an in situ compatibilized blend using ethylene methyl acrylate copolymer (EMA) as the compatibilizer. Effect of EMA on blends of ester type and ether type TPU with PDMS was studied. From the results obtained from torque rheometry, mechanical property evaluation, fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and scanning electron microscopy (SEM), it was concluded that 5 wt% of compatibilizer effectively compatibilized an 80: 20 blend of ester type TPU and PDMS, whereas similar blend of ether type TPU required only 2 wt% compatibilizer.
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    Development of non-toxic latex formulation for biomedical applications ( Project - 7003 )
    (SCTIMST, 2004-07-31) Mohanan, PV; Roy, Joseph; Ramesh, P; Mira, Mohanty; Kumari, TV
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    Dynamic mechanical properties of hydroxyapatite-ethylene vinyl acetate copolymer composites
    (MATERIALS CHEMISTRY AND PHYSICS, 2005) Velayudhan, S; Ramesh, P; Varma, HK; Friedrich, K
    Dynamic mechanical thermal analysis (DMTA) was carried out to explore the dependence of temperature on the viscoelasticity of composites consisting of synthetic hydroxyapatite (HAP) particulate filled ethylene vinyl acetate copolymer (EVA). Two forms of HAP, differing in their surface characteristics and particle size, were used for the study. The freeze-dried HAP (FDHAP) had a mean particle size of 49.18 mum and an irregular surface morphology. In the contrary the spray dried form of HAP (SDHAP) had a mean particle size of 5.84 (m and a spherical morphology. The dynamic mechanical analysis of the composites showed that both, particle size and morphology, had a significant effect on viscoelastic properties. A tremendous increase of the storage modulus was noted with the addition of HAP. Above the T-g of the polymer matrix, the values were marginally higher for the composites containing FDHAP than for those with SDHAP. The damping (tan delta) was found to decrease with the inclusion of HAP. A marginal upper shift in the value of the glass transition temperature (T-g) was observed for the composites fabricated from SDHAP indicating a slightly strong interaction between this HAP and the EVA matrix. (C) 2004 Elsevier B.V. All rights reserved.
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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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    Effect of photografting 2-hydroxyethyl acrylate on the hemocompatibility of electrospun poly(ethylene-co-vinyl alcohol) fibroporous mats
    (MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 2016) Mayuri, PV; Bhatt, A; Joseph, R; Ramesh, P
    Poly(ethylene-co-vinyl alcohol) (EVAL) has been recommended as a material suitable for blood contacting applications. Effect of ethylene content and associated hydrophobicity of EVAL on the blood-material interactions have been documented in the literature. In this work, surface chemistry of EVAL substrate was altered by photografting a hydrophilic monomer, 2-hydroxyethyl acrylate (HEA) with the aid of a photoinitiator, benzophenone (BP), and the effect of surface modification on the blood-material interactions was investigated. Since the modified material was intended to be used as leukodepletion filters, a solution containing EVAL, HEA and BP was electrospun into fibroporous mats and UV treated to induce grafting. Degree of grafting, bonding between fibers and fiber diameter increased with increase in UV exposure time whereas mechanical properties showed a decreasing trend. Decreased water contact angle indicated improved wetting characteristics. In vitro hemocompatibility tests revealed that the modified EVAL surface exhibited significantly lower hemolytic activity, protein adsorption and platelet adhesion than neat EVAL. The modification did not have any substantial effect on the activation of the complement system and coagulation parameters. Photografting led to significant reduction in the adhesion of red blood cells (RBC) whereas white blood cell (WBC) consumption remained above 90%. The results implied that photografting HEA on EVAL substantially improves hemocompatibility of EVAL and when it is used as a filter, it selectively removes leukocytes and allows easy passage of other blood components. (C) 2015 Elsevier B.V. All rights reserved.
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    Effect of photografting 2-hydroxyethylacrylate on the hemocompatibility of electrospun poly(ethylene-co-vinyl alcohol) fibroporous mats
    (Materials Science and Engineering, 2015-11) Mayuri, PV; Bhatt, A; Joseph, R; Ramesh, P
    Poly(ethylene-co-vinyl alcohol) (EVAL) has been recommended as a material suitable for blood contacting applications. Effect of ethylene content and associated hydrophobicity of EVAL on the blood–material interactions have been documented in the literature. In this work, surface chemistry of EVAL substrate was altered by photografting a hydrophilic monomer, 2-hydroxyethyl acrylate (HEA) with the aid of a photoinitiator, benzophenone (BP), and the effect of surface modification on the blood–material interactions was investigated. Since the modified material was intended to be used as leukodepletion filters, a solution containing EVAL, HEA and BP was electrospun into fibroporous mats and UV treated to induce grafting. Degree of grafting, bonding between fibers and fiber diameter increased with increase in UV exposure time whereas mechanical properties showed a decreasing trend. Decreased water contact angle indicated improved wetting characteristics. In vitro hemocompatibility tests revealed that the modified EVAL surface exhibited significantly lower hemolytic activity, protein adsorption and platelet adhesion than neat EVAL. The modification did not have any substantial effect on the activation of the complement system and coagulation parameters. Photografting led to significant reduction in the adhesion of red blood cells (RBC) whereas white blood cell (WBC) consumption remained above 90%. The results implied that photografting HEA on EVAL substantially improves hemocompatibility of EVAL and when it is used as a filter, it selectively removes leukocytes and allows easy passage of other blood components
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    Effect of Surface Functionalization on the Physicomechanical Properties of a Novel Biofunctional Copolymer
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2011) Sailaja, GS; Ramesh, P; Varma, H
    The physicomechanical properties of functionally active poly(hydroxyethyl methacrylate-co-methyl methacrylate) [poly(HEMA-co-MMA)] are evaluated. It has been reported that the surface phosphorylated poly(HEMA-co-MMA) is capable of eliciting direct bone bonding when implanted in vivo. Hence, it is important to examine the physicomechanical property of the copolymer as a function of surface modification. The properties assessed are differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), equilibrium swelling, compressive strength, and dynamic mechanical analysis. According to the DSC data, the glass transition temperature, T-g of poly(HEMA-co-MMA) is not significantly altered by surface phosphorylation. The TGA results demonstrated that unmodified and surface phosphorylated copolymers have similar degradation profile. The differential thermal analysis further supports the data. The equilibrium swelling of functionalized poly(HEMA-co-MMA) in phosphate buffer saline ascertained that surface phosphorylation significantly increased the hydrophilicity of the copolymer. The study further illustrated that the percentage of equilibrium swelling appreciably increases with increase in HEMA content in the copolymer and reached a plateau after 100 h. Both compressive strength and compressive modulus of poly (HEMA-co-MMA) decreased due to surface phosphorylation while dynamic storage modulus value was not altered. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 3509-3515, 2011
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    Effect of vinyl acetate content on the sintering behavior of hydroxyapatite-ethylene vinyl acetate copolymer composites
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 2002)
    Ethylene vinyl acetate copolymer (EVA) alone could be used as a binder material for the fabrication of hydroxyapatite (HAP) into intricate shapes for various bone substitute applications. It was observed that as the vinyl acetate content in the polymer was increased from 12 to 28 wt % an increase in the sintered density of the HAP was observed. Retention of the shapes of HAP in the molded form was also observed. (C) 2002 Kluwer Academic Publishers.
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    Electrospun biodegradable calcium containing poly(ester-urethane)urea: Synthesis, fabrication, in vitro degradation, and biocompatibility evaluation
    (JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A, 2013) Nair, PA; Ramesh, P
    In this work an in vitro degradable poly(ester-urethane)urea (PEUU) was synthesized using polycaprolactone diol, hexamethylene diisocyanate, and calcium salt of p-aminobenzoic acid. The synthesized polymer was characterized by 1H-NMR and FTIR spectroscopy and viscosity studies. Scaffolds having random micro fibrous structures were fabricated from PEUU by electrospinning process. The thermal properties of the scaffold were evaluated by thermogravimetric analysis and dynamic mechanical analysis. The mechanical property evaluation showed that the scaffold possess sufficiently high tensile strength of 16 MPa. The in vitro degradation studies of the electrospun scaffold were carried out in phosphate buffer saline for 6 months. The average mass loss of the scaffold after 6 months of hydrolytic degradation was 25%. FTIR spectroscopy study confirmed the degradation of the PEUU from decrease in intensity of 1400 cm1 peak corresponding to ionic carboxylate group. Presence of amine group and calcium ions in the degradation medium further confirmed the degradation of the hard segment in the hydrolytic medium. The mechanical property evaluation of the scaffold indicated a gradual decrease in tensile strength and modulus whereas percentage elongation of the scaffold increases with time of in vitro degradation. The morphological evaluation of the scaffold after degradation by SEM shows evidence of broken fibers and pores in the scaffold. Preliminary in vitro cytotoxicity test demonstrated that both the material and the degradation products were noncytotoxic in nature and the material showed good proliferation to L-929 cells. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
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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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    Fabrication and characterization of silver nanoparticle impregnated uniaxially aligned fibre yarns by one-step electrospinning process
    (Journal of Materials Science, 2016-01) Mayuri, PV; Ramesh, P
    Generating aligned fibres by traditional electrospinning setup is a significant topic which demands serious consideration. A versatile approach for the generation of uniaxially aligned electrospun fibre yarns by simply altering the electrostatic properties of the polymer solution was discussed in this work. Uniaxially aligned electrospun poly(ethylene-co-vinyl alcohol) (EVAL) fibre yarns were fabricated by one-step electrospinning setup. The alignment was accomplished by increasing the solution conductivity by the addition of AgNO3 to the solution. The jet produced was highly stable and followed a straight path, owing to the enhanced solution conductivity. High degree of fibre alignment was obtained even at low surface velocity of the collector. Subsequently the fibre yarns were thermally reduced to obtain silver nanoparticles (Ag NPs) on the surface of the fibres. The so produced Ag NPs incorporated EVAL fibre yarns were characterized by thermogravimetic analysis, energy dispersive X-ray analysis and scanning electron microscopy. The aligned fibre yarns also exhibited excellent mechanical strength. The method could be recommended for the simultaneous generation of aligned and Ag NPs impregnated fibre yarns for broad spectrum of applications.
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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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    Mechanical characterization of high performance graphene oxide incorporated aligned fibro porous polycarbonate urethane membrane for potential biomedical applications
    (Journal of Applied Polymer Science, 2015-04) Thampi, S; Muthuvijayan, V; Ramesh, P
    In this article, we report the development of graphene oxide (GO) reinforced electrospun poly(carbonate urethane) (PCU) nanocomposite membranes intended for biomedical applications. In this study, we aimed to improve the mechanical properties of PCU fibroporous electrospun membranes through fiber alignment and GO incorporation. Membranes with 1, 1.5, and 3% loadings of GO were evaluated for their morphology, mechanical properties, crystallinity, biocompatibility, and hemocompatibility. The mechanical properties were assessed under both static and dynamic conditions to explore the tensile characteristics and viscoelastic properties. The results show that GO presented a good dispersion and exfoliation in the PCU matrix, contributing to an increase in the mechanical performance. The static mechanical properties indicated a 55% increase in the tensile strength, a 127% increase in toughness for 1.5 wt % GO loading and the achievement of a maximum strength reinforcement efficiency value at the same loading. Crystallinity changes in membranes were examined by X-ray diffraction analysis. In vitro cytotoxicity tests with L-929 fibroblast cells and percentage hemolysis tests with fresh venous blood displayed the membranes to be cytocompatible with acceptable levels of hemolytic characteristics. Accordingly, these results highlight the potential of this mechanically improved composite membrane’s application in the biomedical field
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    Mechanical Properties of Hydroxyapatite-Filled Ethylene Vinyl Acetate Copolymer Composites: Effect of Particle Size and Morphology
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2011) Velayudhan, S; Ramesh, P; Varma, HK
    Pliable and bioactive composites made of hydroxyapatite (HAP) and ethylene vinyl acetate (EVA) copolymer were developed for the repair of defective cranium. This article describes the mechanical properties of HAP-EVA composites. The effects of HAP particle size and morphology of HAP on the properties of resultant composites were investigated using various techniques. It was found that the composites containing smaller HAP particles had higher values of tensile modulus, flexural modulus, and impact strength. Examination of the fracture surfaces revealed that only a mechanical bond existed between the filler and the matrix. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 1594-1601, 2011