Browsing by Author "James, NR"

Now showing 1 - 16 of 16
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    A photochemical method for immobilization of azidated dextran onto aminated poly(ethylene terephthalate) surfaces
    (POLYMER INTERNATIONAL, 2008) Bhat, VT; James, NR; Jayakrishnan, A
    BACKGROUND: Dextran, a bacterial polysaccharide, has been reported to be as good as poly(ethylene glycol) in its protein-rejecting and cell-repelling abilities. In addition, the multivalent nature of dextran is advantageous for surface grafting of biologically active molecules. We report here a method to photochemically bind dextran hydrogel films to aminated poly(ethylene terephthalate) (PET) surfaces in aqueous media using a heterobifunctional crosslinker, 4-azidobenzoic acid. In order to achieve this, dextran was first functionalized with the crosslinker using carbodiimide chemistry followed by photo-crosslinking and immobilization onto the nucleophile-rich aminated PET surfaces. RESULTS: The presence of the immobilized dextran on PET was verified by attenuated total-reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and contact angle measurements. The grafted surface was highly hydrophilic due to the heavily hydrated polysaccharide network on the surface as demonstrated by the near zero water contact angle. CONCLUSION: A photochemical method for surface immobilization of dextran onto aminated PET using aryl azide chemistry is a facile technique to generate highly hydrophilic and more hemocompatible surfaces. The aryl nitrenes generated by photolysis produce a metastable, electron-deficient intermediate, azacycloheptatetraene, which is believed to be responsible for the simultaneous crosslinking of dextran and its immobilization onto the aminated PET surface. The aryl azide chemistry reported here for dextran could be useful as a versatile technique for surface modification of other nucleophile-rich polymers to create dextran- or similar polysaccharide-immobilized surfaces. (c) 2007 Society of Chemical Industry.
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    Galactosylated alginate-curcumin micelles for enhanced delivery of curcumin to hepatocytes
    (INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES, 2016) Sarika, PR; James, NR; Kumar, PRA; Raj, DK
    Galactosylated alginate-curcumin conjugate (LANH(2)-Alg Ald-Cur) is synthesized for targeted delivery of curcumin to hepatocytes exploiting asialoglycoprotein receptor (ASGPR) on hepatocytes. The synthetic procedure includes oxidation of alginate (Alg), modification of lactobionic acid (LA), grafting of targeting group (modified lactobinic acid, LANH(2)) and conjugation of curcumin to alginate. Alginate-curcumin conjugate (Alg-Cur) without targeting group is also prepared for the comparison of properties. LANH(2)-Alg Ald-Cur self assembles to micelle with diameter of 235 +/- 5 nm and zeta potential of -29 mV in water. Cytotoxicity analysis demonstrates enhanced toxicity of LANH(2)-Alg Ald-Cur over Alg-Cur on HepG2 cells. Cellular uptake studies confirm that LANH(2)-Alg Ald-Cur can selectively recognize HepG2 cells and shows higher internalization than Alg-Cur conjugate. Results indicate that LANH(2)-Alg Ald-Cur conjugate micelles are suitable candidates for targeted delivery of curcumin to HepG2 cells. (C) 2016 Elsevier B.V. All rights reserved.
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    Galactosylated pullulan-curcumin conjugate micelles for site specific anticancer activity to hepatocarcinoma cells
    (COLLOIDS AND SURFACES B-BIOINTERFACES, 2015) Sarika, PR; James, NR; Nishna, N; Kumar, PRA; Raj, DK
    Galactosylated pullulan curcumin conjugate (LANH(2)-Pu Aid-Cur SA) is developed for target specific delivery of curcumin to hepatocarcinoma cells by five step synthetic strategy, which includes oxidation of pullulan (Pu Ald), introduction of amino group to the targeting ligand (LANH(2)), grafting of the LANH(2) to Pu Aid, modification of curcumin (Cur SA) and conjugation of Cur SA to pullulan. Nongalactosylated pullulan curcumin conjugate (Pu-Cur SA) is also prepared to compare the enhancement in cytotoxicity offered by the targeting group. Both LANH(2)-Pu Aid-Cur SA and Pu-Cur SA conjugates could self assemble to micelle in water with hydrodynamic diameters of 355 +/- 9 nm and 363 +/- 10 nm, respectively. Both conjugates show spherical morphology and enhance stability of curcumin in physiological pH. Compared to Pu-Cur SA, LANH(2)-Pu Aid-Cur SA exhibits higher toxicity and internalization towards HepG2 cells. This indicates the enhanced uptake of LANH(2)-Pu Ald-Cur SA conjugate via ASGPR (asialoglycoprotein receptor) mediated endocytosis into HepG2 cells. (C) 2015 Elsevier B.V. All rights reserved.
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    Gum arabic-curcumin conjugate micelles with enhanced loading for curcumin delivery to hepatocarcinoma cells
    (CARBOHYDRATE POLYMERS, 2015) Sarika, PR; James, NR; Kumar, PRA; Raj, DK; Kumary, TV
    Curcumin is conjugated to gum arabic, a highly water soluble polysaccharide to enhance the solubility and stability of curcumin. Conjugation of curcumin to gum arabic is confirmed by H-1 NMR, fluorescence and UV spectroscopy studies. The conjugate self assembles to spherical nano-micelles (270 +/- 5 nm) spontaneously, when dispersed in aqueous medium. Spherical morphology of the self assembled conjugate is evidenced by field emission scanning electron microscopy and transmission electron microscopy. The self assembly of the amphiphilic conjugate into micelle in aqueous medium significantly enhances the solubility (900 fold of that of free curcumin) and stability of curcumin in physiological pH. The anticancer activity of the conjugate micelles is found to be higher in human hepatocellular carcinoma (HepG2) cells than in human breast carcinoma (MCF-7) cells. The conjugate exhibits enhanced accumulation and toxicity in HepG2 cells due to the targeting efficiency of the galactose groups present in gum arabic. (C) 2015 Elsevier Ltd. All rights reserved.
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    Microgravity as a means to incorporate HepG2 aggregates in polysaccharide-protein hybrid scaffold
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 2016) Sarika, PR; James, NR; Anilkumar, PR; Raj, DK; Kumary, TV
    Tissue culture under microgravity provides a venue which promotes cell-cell association while avoiding the detrimental effects of high shear stress. Hepatocytes cultured on carriers or entrapped within matrices under simulated microgravity conditions showed improved cell function and proliferation. In the present study, a new approach was adopted where a non-cell adherent scaffold was incorporated with hepatospheroids (HepG2) under microgravity. Gum arabic (GA) was cross-linked with gelatin (GA-Gel) and collagen (GA-Col) to prepare non-cell adherent scaffolds. Microgravity experiments with GA-Gel and GA-Col indicated that GA-Col is a better substrate compared to GA-Gel. Microgravity experiments of GA-Col scaffolds with HepG2 cells confirmed that the non-adherent surface with porous architecture can incorporate hepatocyte spheroids and maintain liver specific functions. Albumin and urea synthesis of hepatocytes was sustained up to 6 days under microgravity conditions in the presence of GA-Col scaffold. This new approach of using non-cell adherent matrix and microgravity environment for developing biological substitutes will be beneficial in tissue engineering, bioartificial liver devices and in vitro safety assessment of drugs.
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    Modified dextran cross-linked electrospun gelatin nanofibres for biomedical applications
    (CARBOHYDRATE POLYMERS, 2014) Jalaja, K; Kumar, PRA; Dey, T; Kundu, SC; James, NR
    Electrospun gelatin nanofibres attract attention of bioengineering arena because of its excellent biocompatibility and structural resemblance with native extracellular matrix. In this study, we have developed gelatin nanofibres using an innovative cross-linking approach to minimize cytotoxic effects. Gelatin was dissolved in water:acetic acid (8:2, v/v) solution and electrospun to form nanofibres with diameter in the range of 156 +/- 30 nm. The nanofibres were cross-linked with a modified polysaccharide, namely, dextran aldehyde (DA). Cross-linking with DA could be achieved without compromising the fibrous architecture. DA cross-linked gelatin nanofibres maintained the fibrous morphology in aqueous medium. These mats exhibit improved mechanical properties and gradual degradation behaviour. The nanofibres were evaluated for cytotoxicity, cell adhesion, viability, morphology and proliferation using L-929 fibroblast cells. The results confirmed that DA cross-linked mats were non cytotoxic towards L-929 cells with good cell adhesion, spreading and proliferation. (C) 2014 Elsevier Ltd. All rights reserved.
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    Modified gum arabic cross-linked gelatin scaffold for biomedical applications
    (MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 2014) Sarika, PR; Cinthya, K; Jayakrishnan, A; Anilkumar, PR; James, NR
    The present work deals with development of modified gum arabic cross-linked gelatin scaffold for cell culture. A new biocompatible scaffold was developed by cross-linking gelatin (Gel) with gum arabic, a polysaccharide. Gum arabic was subjected to periodate oxidation to obtain gum arabic aldehyde (GAA). GAA was reacted with gelatin under appropriate pH to prepare the cross-linked hydrogel. Cross-linking occurred due to Schiff's base reaction between aldehyde groups of oxidized gum arabic and amino groups of gelatin. The scaffold prepared from the hydrogel was characterized by swelling properties, degree of cross-linking, in vitro degradation and scanning electron microscopy (SEM). Cytocompatibility evaluation using L-929 and HepG2 cells confirmed non-cytotoxic and non-adherent nature of the scaffold. These properties are essential for generating multicellular spheroids and hence the scaffold is proposed to be a suitable candidate for spheroid cell culture. (C) 2014 Elsevier B.V. All rights reserved.
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    Nanogels based on alginic aldehyde and gelatin by inverse miniemulsion technique: synthesis and characterization
    (CARBOHYDRATE POLYMERS, 2015) Sarika, PR; Kumar, PRA; Raj, DK; James, NR
    Nanogels were developed from alginic aldehyde and gelatin by an inverse miniemulsion technique. Stable inverse miniemulsions were prepared by sonication of noncontinuous aqueous phase (mixture of alginic aldehyde and gelatin) in a continuous organic phase (Span 20 dissolved in cyclohexane). Cross-linking occurred between alginic aldehyde (M) and gelatin (gel) in the presence of borax by Schiff's base reaction during the formation of inverse miniemulsion. The effects of surfactant (Span 20) concentration, volume of the aqueous phase and AA/gel weight ratio on the size of the alginic aldehyde-gelatin (AA-gel) nanoparticles were studied. Nanogels were characterized by DLS, FT-IR spectroscopy, TGA, SEM and TEM. DLS, TEM and SEM studies demonstrated nanosize and spherical morphology of the nanogels. Hemocompatibility and in vitro cytocompatibility analyses of the nanogels proved their nontoxicity. The results indicated the potential of the present nanogel system as a candidate for drug- and gene-delivery applications. (C) 2014 Elsevier Ltd. All rights reserved.
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    Polyurethane thermoplastic elastomers with inherent radiopacity for biomedical applications
    (JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A, 2012) Kiran, S; James, NR; Jayakrishnan, A; Joseph, R
    Synthesis and characterization of three different radiopaque thermoplastic polyurethane elastomers are reported. Radiopacity was introduced to the polyurethanes by incorporating an iodinated chain extender, namely, 4,4'-isopropylidinedi-(2,6-diiodophenol) (IBPA), into the polymer chain during polyurethane synthesis. Radiopaque polyurethanes (RPUs) were synthesized by reacting 4,4'-methylenebis(phenyl isocyanate) (MDI), IBPA, and three different diols. The polyols used for the synthesis were polypropylene glycol, polycaprolactone diol, and poly(hexamethylene carbonate) diol. RPUs were characterized by infrared spectroscopy, contact angle measurements, thermogravimetry, dynamic mechanical analysis, energy dispersive X-ray analysis, gel permeation chromatography, X-ray fluorescence spectroscopy, and X-radiography. X-ray images showed that all RPUs prepared using IBPA as the chain extender are highly radiopaque compared with an Aluminum wedge of equivalent thickness. Elemental analysis revealed that the polyurethanes contained 1819% iodine in the polymer matrix. The RPUs developed have radiopacity equivalent to that of a polymer filled with 20 wt % barium sulfate. Results revealed that RPUs of wide range of properties may be produced by incorporating different diols as the soft chain segment. Cell culture cytotoxicity studies conducted using L929 cells by direct contact test and MTT assay proved that these RPUs are noncytotoxic in nature. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2012.
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    Polyurethanes with radiopaque properties
    (BIOMATERIALS, 2006)
    An aliphatic, commercially available, medical grade polyurethane, Tecoflex 80 A was made radiopaque by coupling a 5-iodine-containing molecule, N-(2,6- diiodocarboxyphenyl)-3,4,5-triiodo benzamide (DCPTB) onto the polymer backbone. DCPTB was synthesized by coupling 4-ainino-3,5-diiodobenzoic acid and 3,4,5-triiodobenzoic acid using dicyclohexyl carbodiimide. Radiopaque polyurethane thus obtained was characterized by IR, TGA, DSC and X-radiography. By optimizing the reaction conditions, it was possible to incorporate about 8% iodine in the polymer (wt/wt) to achieve radiopacity almost equivalent to that of a 2mm thick aluminium wedge. However, the products differed from the starting polymer in thermal characteristics. The starting polymer showed two endothermic transitions, the first one due to glass transition of the soft segment and the second one due to disruption of the hard segments. After modification, the second transition shifted to a lower temperature, while the first transition remained unaltered. Also, the modified polymers showed reduced thermal stability compared to the starting polymer. These observations could be explained on the basis of the reduced extent of intermolecular hydrogen bonding among the hard segments of the end product. Radiopaque polyurethanes are expected to have significant advantage over their non-radiopaque counterparts in many medical and related applications. (c) 2005 Elsevier Ltd. All rights reserved.
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    Preparation and evaluation of photocrosslinkable chitosan as a drug delivery matrix
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2002) Jameela, SR; Lakshmi, S; James, NR; Jayakrishnan, A
    Epichlorohydrin (1-chloro-2,3-epoxypropane) was reacted with sodium azide in the presence of a phase transfer catalyst to obtain 1-cliloro-2-hydroxy-3-azidopropane, which was further coupled onto chitosan to prepare. a photocrosslinkable derivative of the biopolymer. Elemental analysis and infrared (IR) spectroscopy confirmed the incorporation of azide groups onto chitosan. Films were cast from an aqueous acetic acid solution of azidated chitosan containing a model drug, such as theophylline. Irradiation of the film with ultraviolet (UV) light led to crosslinking of the drug incorporated film. IR spectra indicated complete surface crosslinking within 2 h of irradiation. Release of theophylline from uncrosslinked and crosslinked films was examined in simulated gastric and intestinal fluids without enzymes at 37 degreesC. The release of the drug from the crosslinked films was slower than the release from uncrosslinked films. Although the system is far from being optimized to obtain sustained release of a pharmacologically active agent for long periods, the data obtained indicate the possibility of developing photocrosslinkable matrices of biopolymers, such as chitosan, for sustained drug delivery with many advantages over chemical crosslinking. (C) 2002 Wiley Periodicals, Inc.
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    Preparation, characterization and biological evaluation of curcumin loaded alginate aldehyde-gelatin nanogels
    (MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 2016) Sarika, PR; James, NR; Kumar, PRA; Raj, DK
    Curcumin, a natural polyphenol exhibits chemopreventive and chemotherapeutic activities towards cancer. In order to improve the bioavailability and therapeutic efficacy, curcumin is encapsulated in alginate aldehyde-gelatin (Alg Ald-Gel) nanogels. Alginate aldehyde-gelatin nanogels are prepared by inverse miniemulsion technique. Physicochemical properties of the curcumin loaded nanogels are evaluated by, Dynamic light scattering (DLS), NMR spectroscopy and Scanning electron microscopy (SEM). Curcumin loaded nanogels show hydrodynamic diameter of 431 +/- 8 nm and a zeta potential of 36 +/- 4 my. The prepared nanogels exhibit an encapsulation efficiency of 72 +/- 2%. In vitro drug release studies show a controlled release of curcumin from nanogels over a period of 48 h. Hemocompatibility and cytocompatibility of the nanogels are evaluated. Bare nanogels are cytocompatible and curcumin loaded nanogels induce anticancer activity towards MCF-7 cells. In vitro cellular uptake of the curcumin loaded nanogels using confocal laser scanning microscopy (CLSM) confirms the uptake of nanogels in MCF-7 cells. Hence, the developed nanogel system can be a suitable candidate for curcumin delivery to cancer cells. (C) 2016 Elsevier B.V. All rights reserved.
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    Surface thiocyanation of plasticized poly(vinyl chloride) and its effect on bacterial adhesion
    (BIOMATERIALS, 2003)
    Thiocyanates, especially bis-alkylthiocyanates are highly effective in killing a number of bacterial strains and are reported to be potent biocides at ppm concentrations. In order to examine whether a covalently bound and immobilized thiocyanate group on a biomaterial surface is still effective as a bactericide, plasticized poly(vinyl chloride) (PVC) was thiocyanated using sodium thiocyanate in the presence of a phase transfer catalyst in aqueous media leading to the nucleophilic substitution of chlorine by thiocyanate on the PVC surface. Thiocyanation imparted hydrophilicity to the surface in comparison with bare PVC. Control and thiocyanated PVC surfaces were exposed to two strains of bacteria commonly implicated in device-associated infections, such as Staphylococcus aureus and Staphylococcus epidermidis. Bacterial adhesion and colonization was quantitated by counting the viable organisms on the adhered surface as well as by optical and scanning electron microscopy. Significantly reduced retention of S. epidermidis and S. aureus was seen on the thiocyanated PVC surface. Immobilized thiocyanate was non-cytotoxic in a preliminary cell culture assay. The study thus showed that even though an immobilized thiocyanate moiety on the polymer surface was not as effective as a bactericide unlike soluble thiocyanates, it prevented the retention and colonization of the bacteria to a considerable extent. (C) 2003 Elsevier Science Ltd. All rights reserved.
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    Synthesis and polymerization of a new iodine-containing monomer
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2003) Lakshmi, S; James, NR; Nisha, VS; Jayakrishnan, A
    A new iodine-containing methacrylate monomer, 3,4,5-triiodobenzoyloxyethyl methacrylate (TIBEM), was synthesized by coupling 2-hydroxyethyl methacrylate (HEMA) with 3,4,5-triiodobenzoic acid. The monomer was characterized by H-1 nuclear magnetic resonance, infrared (IR), and ultraviolet spectra. Homopolymerization and copolymerization of the monomer with methyl methacrylate (MMA) were carried out using 2,2'-azobis isobutyronitrile as the initiator. A terpolymer of TIBEM, MMA, and HEMA was also synthesized. The copolymers were characterized by IR, gel permeation chromatography, differential thermal analysis, and thermogravimetric analysis (TGA). High molecular weight polymers were produced with MMA at different feed compositions of TIBEM. The polymers were found to be freely soluble in common solvents for acrylic polymers. TGA showed little decomposition of the copolymer below 280degreesC. Copolymers showed good radiopacity at 25 wt % of TIBEM in the feed. These copolymers could find applications in medical and dental areas where radiopacity is a desirable feature of the implants. (C) 2003 Wiley Periodicals, Inc.
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    Synthesis, polymerization, and copolymerization of aliphatic vinyl azide
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2003) James, NR; Jayakrishnan, A
    The synthesis and characterization of a fully aliphatic polymeric azide by polymerization of its vinyl monomer 1,3-diazidoisopropyl methacrylate (DAIPM) is reported. DAIPM was prepared by azidation of epichlorohydrin followed by coupling with methacrylic acid. Homopolymer and copolymers with methyl methacrylate were prepared and characterized by IR, GPC, TGA, DTA, and elemental analyses. These polymers are freely soluble in organic solvents like dichloromethane, tetrahydrofuran, di-methyl formamide, acetone, and so forth and do not crosslink on storing. The polymers show decreased thermal stability with an increase in azide content and undergo exothermic decomposition on heating. (C) 2003 Wiley Periodicals, Inc. Inc.
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    Tween 20-modified poly(vinyl chloride) exhibits enhanced blood-compatibility
    (POLYMER INTERNATIONAL, 2005) Balakrishnan, B; James, NR; Jayakrishnan, A
    Poly(vinyl chloride) (PVC) resin was modified by grafting the non-ionic surfactant poly(oxyethylene 20 sorbitan) monolaurate (Tween (R) 20) using isocyanate chemistry. PVC was aminated using ethylenediamine and coupled with hexamethylene diisocyanate. Tween 20 was then reacted with the polymer, resulting in the grafting of the surfactant. The polymer modification was confirmed using infrared and X-ray photo-electron spectroscopy. Films of modified polymer were cast from a solution of tetrahydrofuran. The surface of films prepared from the modified polymer showed increased hydrophilicity as evidenced by contact-angle measurements. The solid/water free energy of the modified polymer surface was nearly a quarter of the energy of the bare PVC surface. Static platelet adhesion studies using platelet-rich plasma demonstrated significantly reduced adhesion onto a modified PVC surface compared with unmodified PVC. Data obtained demonstrate that modification of polymers with Tween 20 may be an interesting way of imparting protein- and cell-repelling characteristics to them, thereby improving their blood-compatibility. (c) 2005 Society of Chemical Industry.