A.K. Banthia

Preparation and characterization of polyvinyl alcohol-gelatin hydrogel membranes for biomedical applications.

The purpose of this research was to design and develop hydrogels by esterification of polyvinyl alcohol (PVA) with gelatin. The membranes were characterized by Fourier Transform Infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and differential scanning calorimetry. The viscosity of the esterified product (as solution) was compared with the mixture of PVA and gelatin of the same composition. The mechanical properties of the hydrogels were characterized by tensile tests. Swelling behavior and hemocompatibility of the membrane were also evaluated. The diffusion coefficient of salicylic acid (SA), when the receptor compartment contained Ringers solution, through the membrane was determined. SA was used as a model drug. FTIR spectra of the membranes indicated complete esterification of the free carboxylic groups of gelatin. XRD studies indicated that the crystallinity of the membranes was mainly due to gelatin. The comparison of viscosity indicated an increase in segment density within the molecular coil. The membrane had sufficient strength and water-holding capacity. Hemocompatibility suggested that the hydrogel could be tried as wound dressing and as an implantable drug delivery system. The diffusion coefficient of SA through the membrane was found to be 1.32×10−5 cm2/s. The experimental results indicated that the hydrogel could be tried for various biomedical applications.

Polymeric Hydrogels: Characterization and Biomedical Applications

Hydrogels are cross-linked polymeric networks, which have the ability to hold water within the spaces available among the polymeric chains. The hydrogels have been used extensively in various biomedical applications, e.g., drug delivery, cell carriers and/or entrapment, wound management and tissue engineering. Though far from extensive, this article has been devoted to study the common methods used for the characterization of the hydrogels and to review the range of applications of the same in health care.

Toughened epoxy adhesive modified with acrylate based liquid rubber

The adhesive and mechanical properties of epoxy resins modified with carboxyl terminated poly(2-ethylhexyl acrylate) (CTPEHA) liquid rubber have been investigated as a function of the concentration of liquid rubber. CTPEHA was synthesized by the bulk polymerization technique. CTPEHA oligomer was prereacted with the epoxy and the modified epoxy networks were made by curing with an ambient temperature curing agent. The modified epoxy networks were evaluated with respect to their adhesive and mechanical properties. The optimum properties were obtained at about 10–15 phr (phr stands for parts per hundred parts of epoxy resin) concentration of modifier. Fracture surface analysis by optical microscopy (OM) indicates the presence of two phase microstructures. © 2000 Society of Chemical Industry

Epoxidized soybean oil toughened epoxy adhesive

Epoxidized soybean oil (ESO) has been used to toughen epoxy resin cured with ambient temperature hardener, Tris-2,4,6-(N,N-dimethyl amino methyl) phenol. The ESO was prepolymerized with the amine hardener to obtain the liquid epoxidized soybean rubber (ESR). The ESR modified epoxy networks were evaluated for their thermal, impact and adhesion properties. The epoxy/ESR compositions were systematically varied to study the effect of modifier concentration on the adhesion and impact strength. The optimum properties were obtained at a concentration of 20 wt% ESR. The DSC and DMTA analyses indicate phase separation between the epoxy-rich phase and ESO-rich phase.

Polyvinyl alcohol--gelatin patches of salicylic acid: preparation, characterization and drug release studies.

Polyvinyl alcohol—gelatin patches were developed and salicylic acid was incorporated at different stages of preparation of the patches. The patches were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry, tensile strength test, and scanning electron microscopy. The release patterns of the drug from the patches were also studied. The FTIR spectra of the blank patch indicated complete esterification of the free carboxylic groups of gelatin. The XRD studies indicated a crystalline form of the drug entrapped in the patches. Release of the drug from the patches followed Higuchian/Fickian kinetics indicating a diffusion-controlled release process.

Development of carboxymethyl cellulose acrylate for various biomedical applications.

The purpose of this work is to prepare a pH-sensitive hydrogel membrane of sodium carboxymethyl cellulose acrylate for drug delivery and other biomedical applications. The hydrogel was made by esterification of sodium carboxymethyl cellulose (SCMC) and acryloyl chloride (ACl). The esterified product was characterized by FTIR spectroscopy and XRD. Swelling, hemocompatibility, water vapor transmission rate, contact angle and diffusional studies were also done. Biocompatibility of the membrane was established by quantification of cell growth of L929 cells and mice splenocytes. The FTIR spectrum of the hydrogel suggested the formation of ester bonds between the hydroxyl groups of sodium carboxymethyl cellulose and the carbonyl group of acryloyl chloride. Water vapor transmission rate, hemocompatibility, contact angle and swelling studies indicated that the hydrogel can be tried as a wound dressing material. The hydrogel showed pH-dependent swelling behavior arising from the acidic pendant group in the polymer network. The permeability of the hydrogel membrane produced, as shown by salicylic acid diffusion, increased in response to an increase in pH of the external medium. The hydrogel membrane was permeable to salicylic acid at pH 7.2 but not at pH 2.0 (0.01N HCl). The effect of changes of pH on the hydrogels permeability was found to be reversible. The hydrogel membrane was found to be compatible with the L929 mice fibroblast cell line and mice splenocytes. The esterified product of SCMC and ACl swells on increase of pH indicating its possible use in a pH-sensitive drug delivery system and as a wound dressing material.

Development and Characterization of Chitosan based Polymeric Hydrogel Membranes

The current study deals with the development of a glutaraldehyde cross-linked chitosan-based delivery system with improved mechanical properties utilizing the reactive solvent technique. The prepared systems were characterized by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The systems were also analysed for mechanical and pH-dependent swelling properties and they were also analysed for their haemocompatibility and cytocompatibility. FT-IR studies indicated formation of imine bonds during the cross-linking reaction of chitosan and glutaraldehyde. TGA, XRD and mechanical studies indicated optimal properties for the system prepared with 5% methacrylic acid as reactive solvent. The developed systems indicated pH-dependent swelling behaviour with increased swelling at lower pH. The prepared delivery systems were found to be highly haemocompatible in the presence of human blood and cytocompatible in the presence of L929 fibroblast cells. The release of the model drug (salicylic acid) from the delivery systems in 0.01 M HCl indicated Fickian kinetics. The developed delivery systems could be used to deliver drugs selectively in the stomach.

Toughening of epoxy resin by modification with 2-ethylhexyl acrylate–acrylic acid copolymers

2-Ethylhexyl acrylate–acrylic acid copolymers, ie carboxyl randomized poly(2-ethylhexyl acrylate) (CRPEHA) (LR-1 to LR-6), with different molecular weights and functionality were synthesized. The liquid rubbers were characterized by FTIR spectroscopic analysis, non-aqueous titration, vapour pressure osmometry (VPO) and viscosity measurements. All the liquid rubbers were reacted with the epoxy resin in 10:100 weight ratio using triphenyl phosphine as a catalyst. The modified epoxy networks were made by reacting the homogeneous prereacted resin with an ambient temperature hardener, triethylene tetramine (HY 951). The effect of the molecular weight and functionality of the liquid rubbers on the thermal and impact properties of the modified networks was investigated. © 2000 Society of Chemical Industry

Polyvinyl alcohol–glycine composite membranes: preparation, characterization, drug release and cytocompatibility studies

The purpose of this study was to prepare a polyvinyl alcohol-glycine composite membrane to deliver glycine directly to a site of injury to be utilized for the synthesis of collagen for complete healing of a wound. Polyvinyl alcohol (PVA) and glycine (Gly) blended composite membranes, with different PVA:glycine ratios (1:0.2, 1:0.4, 1:0.6, 1:0.8 and 1:1 w/w), were prepared using a conventional solution casting technique. Various characterizations namely XRD, DSC, tensile tests and glycine release studies of the membranes were done. MTT assay was done to ensure cytocompatibility of the PVA-Gly (1:0.6) membrane using L929 fibroblast cells and mice splenocytes. XRD study indicated dispersion of crystalline glycine in a relatively less crystalline PVA in the membrane. FTIR spectra showed shifting of the hydroxyl peak of PVA from 3430 cm(-1) to 3171 cm(-1) and 3010 cm(-1) in the membranes, indicating intermolecular hydrogen bonding and viscosity measurements of various mixtures of PVA-Gly in solution also supported the same. DSC indicated no interaction between PVA and Gly. It was found that the tensile strength of the composite membrane decreased with the increase in glycine content though there was a marginal increase in the strength when the PVA:Gly ratio was 1:1. Further increase in the Gly content in the membranes was not possible as a solid physical gel was formed while mixing the solutions of PVA and Gly. Gly release from the membrane was immediate following diffusion-controlled Fickian kinetics. The relative cell proliferation of the L929 cells and mice splenocytes were found to be 2.38 and 2.24, respectively, indicating the cytocompatibility of the membrane.

REPARATION AND CHARACTERIZATION OF AMIDATED PECTIN BASED POLYMER ELECTROLYTE MEMBRANES

The work presents the synthesis and characterization of amidated pectin (AP) based polymer electrolyte membranes (PEM) crosslinked with glutaraldehyde (GA). The prepared membranes are characterized by Fourier transform infrared spectroscopy (FTIR), organic elemental analysis, X-ray diffraction studies (XRD), thermogravimetric analysis (TGA) and impedance spectroscopy. Mechanical properties of the membranes are evaluated by tensile tests. The degree of amidation (DA), molar and mass reaction yields (YM and YN) are calculated based on the results of organic elemental analysis. FTIR spectroscopy indicated the presence of primary and secondary amide absorption bands. XRD pattern of membranes clearly indicates that there is a considerable increase in crystallinity as compared to parent pectin. TGA studies indicate that AP is less thermally stable than reference pectin. A maximum room temperature conductivity of 1.098 × 10-3Scm-1 is obtained in the membrane, which is designated as AP-3. These properties make them good candidates for low cost biopolymer electrolyte membranes for fuel cell applications.