Browsing by Author "Sreenivasan, K"

Now showing 1 - 20 of 93
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    A Cytocompatible Poly(N-isopropylacrylamide-co-glycidylmethacrylate) Coated Surface as New Substrate for Corneal Tissue Engineering
    (JOURNAL OF BIOACTIVE AND COMPATIBLE POLYMERS, 2010) Joseph, N; Prasad, T; Raj, V; Kumar, PRA; Sreenivasan, K; Kumary, TV
    The conventional method of retrieving cells for tissue engineering to create three-dimensional functional tissues uses enzymes that may hamper cell viability and re-adhesion. Culturing cells on thermoresponsive surfaces of poly(N-isopropylacrylamide) (PNIPAAm) is a relatively new nondestructive method of creating in vitro tissues. In this study, PNIPAAm and glycidylmethacrylate (GMA)-based thermoresponsive copolymer N-isopropylacrylamide-co-glycidylmethacrylate (NGMA) were synthesized as a potential cell culture harvesting system for generating 3D synthetic tissues. The copolymer was characterized by differential scanning calorimetry, gel permeation chromatography, Fourier transform infrared spectroscopy, water contact angle, atomic force microscopy, and nuclear magnetic resonance spectroscopy. The NGMA-coated dishes were evaluated for cytotoxicity and cytocompatibility using L-929 cells. Primary rabbit corneal cultures established on NGMA surface were detached as an intact cell sheet with epithelial specific characteristics as well as maintenance of cell-cell and cell-extracellular matrix contact. The results confirmed the suitability of NGMA substrate for cell culture and temperature-induced cell sheet harvest. This is the first report on this copolymer formulation as a substrate for tissue engineering application. Hydrophobic GMA apart from modulating the lower critical solution temperature features the prospects of further modification, namely the incorporation of biomolecules through the epoxy groups.
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    A filter paper based sensing element to detect beta-cyclodextrin in aqueous and biological fluid
    (JOURNAL OF THE INDIAN CHEMICAL SOCIETY, 1997) Sreenivasan, K
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    A note on the selectivity of gamma-radiation polymerised molecularly imprinted poly (HEMA)
    (POLYMER GELS AND NETWORKS, 1997) Sreenivasan, K
    gamma-radiation was used to synthesise molecularly imprinted poly (2-hydroxy ethyl methacrylate) containing memory sites for testosterone. The high degree of selectivity of the polymer towards testosterone has been demonstrated by studying the interaction of the polymer with a mixture of testosterone and cholesterol, a molecule with a similar ring structure and shape as testosterone. (C) 1997 Elsevier Science Limited.
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    A novel thermoresponsive copolymer as a suitable substrate for tissue reconstruction
    (TISSUE ENGINEERING PART A, 2008) Viji, MV; Vidya, N; Hopkinson, A; Sreenivasan, K; Dua, HS; Kumari, TV
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    A Novel Thermoresponsive Graft Copolymer Containing Phosphorylated HEMA for Generating Detachable Cell Layers
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2010) Abraham, TN; Raj, V; Prasad, T; Kumar, PRA; Sreenivasan, K; Kumary, TV
    A novel polymeric formulation based on N-isopropylacrylamide (NIPAAm), methylmethacrylate (MMA), and phosphorylated hydroxylethyl methacrylate (Phosp-HEMA) was synthesized and characterized. NIPAAm was copolymerized with a known quantity of MMA to form a poly(NIPAAm-MMA) copolymer and was subsequently grafted with Phosp-HEMA by gamma irradiation to a total dose of 0.5 kGy. The thermoresponsive graft copolymer was characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, contact angle measurements, and energy dispersive X-ray analysis. The cytotoxicity of the graft copolymer analyzed using L-929 fibroblast cells showed noncytotoxic response. The cell adhesion on the graft copolymer was studied using rabbit corneal cells (SIRC) and human osteoblasts (HOS). The adhered cells were found to spread leading to the formation of cell layers. The cell layers with intact cell-cell and cell-extra cellular matrix contact were detached by lowering temperature below the lower critical solution temperature (29 degrees C) of the graft copolymer. The viability and morphology of the cells in detached cell sheets were assessed by live dead staining and environmental scanning electron microscopy, respectively. This interesting feature of cell adhesion to form cell layers and cell sheet retrieval is implicit to be due to the properties of phosphate moieties on thermoresponsive copolymer. To the authors knowledge there is no previous report on phosphate moiety containing thermo responsive polymeric formulations which can modulate cell adhesion and cell sheet retrieval. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 52-62, 2010
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    A simple and rapid spectrophotometric method to estimate glutaraldehyde
    (JOURNAL OF THE INDIAN CHEMICAL SOCIETY, 1997) Sreenivasan, K
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    Absorption characteristics of a novel semi-IPN membrane based on beta-cyclodextrin toward testosterone and progesterone
    (JOURNAL OF APPLIED POLYMER SCIENCE, 1997) Sreenivasan, K
    beta-Cyclodextrin was coupled to the -OH group of 2-hydroxyethyl methacrylate using hexamethylene diisocyanate. Segmented polyurethane and the modified monomer were dissolved in dimethylacetamide and subsequently heated to about 80 degrees C in the presence of AIBN to polymerize the modified monomer to form a semi-interpenetrating network. The potential of the new polymer as a membrane was evaluated by studying the sorption of testosterone and progesterone. The preliminary data showed that the polymer could differentiate structurally close molecules with some degree of selectivity, indicating the possibility of exploring further the polymer, particularly as a membrane. (C) 1997 John Wiley & Sons, Inc.
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    Adult Stem Cells on Methacrylic Acid Grafted Cocoon Silky Fibrous Scaffolds
    (Trends in Biomaterials & Artificial Organs., 2010) Mani, S; Nair, MB; Nisha, S; Sreenivasan, K; Jacob, M; John, A
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    Aggregation of gold nanoparticles followed by methotrexate release enables Raman imaging of drug delivery
    (J Nanoparticle Res., 2012-10) Durgadas, CV; Sharma, CP; Paul, W; Rekha, MR; Sreenivasan, K
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    Aggregation of gold nanoparticles followed by methotrexate release enables Raman imaging of drug delivery into cancer cells
    (JOURNAL OF NANOPARTICLE RESEARCH, 2012) Durgadas, CV; Sharma, CP; Paul, W; Rekha, MR; Sreenivasan, K
    This study refers an aqueous synthesis of methotrexate (MTX)-conjugated gold nanoparticles (GNPs), their interaction with HepG2 cells, and the use of Raman imaging to observe cellular internalization and drug delivery. GNPs of average size 3.5-5 nm were stabilized using the amine terminated bifunctional biocompatible copolymer and amended by conjugating MTX, an anticancer drug. The nanoparticles were released MTX at a faster rate in acidic pH and subsequently found to form aggregates. The Raman signals of cellular components were found to be enhanced by the aggregated particles enabling the mapping to visualize site-specific drug delivery. The methodology seems to have potential in optimizing the characteristics of nanodrug carriers for emptying the cargo precisely at specified sites.
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    Alginate stabilized gold nanoparticle as multidrug carrier: Evaluation of cellular interactions and hemolytic potential
    (CARBOHYDRATE POLYMERS, 2016) Dey, S; Sherly, MCD; Rekha, MR; Sreenivasan, K
    This work delineates the synthesis of curcumin (Ccm) and methotrexate (MTX) conjugated biopolymer stabilized AuNPs (MP@Alg-Ccm AuNPs). The dual drug conjugated nano-vector was characterized by FTIR, 1H NMR and UV-vis spectroscopic techniques. Hydrodynamic diameter and surface charge of the AuNPs were determined by DLS analysis and the spherical particles were visualized by TEM. MP@Alg-Ccm AuNPs exhibited improved cytotoxic potential against C6 glioma and MCF-7 cancer cell lines and was found to be highly hemocompatible. MP@Alg-Ccm AuNPs also exhibited active targeting efficiency against MCF-7 cancer cells due to the presence of "antifolate" drug MTX. Thus MP@Alg-Ccm AuNPs may find potential application in targeted combination chemotherapy for the treatment of cancer. The study is also interesting from the synthetic point of view because, here generation of AuNPs was done using "green chemical" alginate and dual drug conjugated AuNPs were created in two simple reaction steps using "green solvent" water. (C) 2015 Elsevier Ltd. All rights reserved.
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    Alginate stabilized gold nanoparticle as multidrug carrier: Evaluationof cellular interactions and hemolytic potential
    (Carbohydrate Polymers, 2015-09) Dey, S; Sherly, MCD; Rekha, MR; Sreenivasan, K
    This work delineates the synthesis of curcumin (Ccm) and methotrexate (MTX) conjugated biopolymer stabilized AuNPs (MP@Alg–Ccm AuNPs). The dual drug conjugated nano-vector was characterized by FTIR, 1H NMR and UV–vis spectroscopic techniques. Hydrodynamic diameter and surface charge of the AuNPs were determined by DLS analysis and the spherical particles were visualized by TEM. MP@Alg–Ccm AuNPs exhibited improved cytotoxic potential against C6 glioma and MCF-7 cancer cell lines and was found to be highly hemocompatible. MP@Alg–Ccm AuNPs also exhibited active targeting efficiency against MCF-7 cancer cells due to the presence of “antifolate” drug MTX. Thus MP@Alg–Ccm AuNPs may find potential application in targeted combination chemotherapy for the treatment of cancer. The study is also interesting from the synthetic point of view because, here generation of AuNPs was done using “green chemical” alginate and dual drug conjugated AuNPs were created in two simple reaction steps using “green solvent” water
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    Alternate method for grafting thermoresponsive polymer for transferring in vitro cell sheet structures
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2007) Kumar, PRA; Sreenivasan, K; Kumary, TV
    Retrieval of cells for various applications involves enzymatic or mechanical methods that hamper the cell-cell and cell-extracellular matrix (ECM) binding. Poly(N-isopropylacrylamide) (PIPAAm) is a known temperature-sensitive polymer that exhibits a lower critical solution temperature (LCST) around 32 degrees C and is hydrophobic over LCST and hydrophilic below LCST. PIPAAm-grafted culture surface can be used for detaching adhered cells by lowering the temperature below LCST. In this study, polymerization and grafting of PIPPAm was done by gamma (7) ray irradiation instead of the conventional method of electron beam irradiation. The efficacy of the grafted surface was confirmed by the successful growth of different cell lines such as L-929, NRK-49F, HOS, and SIRC. The cell sheet structures with intact cell-cell and cell-ECM contact was detached by lowering incubation temperature below 20 degrees C. Live-dead staining of cells before and after transfer showed that cell sheet structures maintained viability. This approach of synthesizing thermoresponsive surface by gamma-ray irradiation method can be used to culture many other cell types and could be utilized to prepare in vitro tissue constructs for bioengineering. (c) 2007 Wiley Periodicals, Inc.
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    An aqueous process to functionalize the surface of poly(vinyl chloride) with hydroxy groups
    (ANGEWANDTE MAKROMOLEKULARE CHEMIE, 1998) Sreenivasan, K
    An aqueous process based on Williamson's synthesis to functionalize the surface of poly(vinyl chloride) (PVC) with hydroxy groups has been discussed. The method involves the conversion of butanol to sodium butoxide, its coupling to the surface of PVC and the subsequent hydrolysis to form hydroxy groups. The material is characterized by FT-IR and scanning electron microscopic methods.
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    An aqueous process to graft 2-hydroxyl ethyl methacrylate onto polyvinyl chloride through its functional group
    (JOURNAL OF APPLIED POLYMER SCIENCE, 1999) Sreenivasan, K
    A simple aqueous method has been discussed to graft 2-hydroxyl ethyl methacrylate (HEMA) onto the surface of polyvinyl chloride through its functional group (-OH). This method involves the conversion of the -OH group of HEMA to -ONa using metallic sodium. The modified surface has been characterized using FT ATR-IR and Scanning electron microscopic methods. The advantage of the method is the feasibility of using the intact double bond of HEMA for further reaction. (C) 1999 John Wiley & Sons, Inc.
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    Application of molecularly imprinted polymer as a drug retaining matrix
    (ANGEWANDTE MAKROMOLEKULARE CHEMIE, 1997) Sreenivasan, K
    Copolymerization by gamma irradiation of 2-hydroxyethyl methacrylate with ethylene glycol dimethacrylate in the presence of hydrocortisone as model drug gave a molecular imprinted polymer (MIP). The hydrocortisone was removed from the matrix with chloroform and incorporated again from methanol solution. Release data show that 96% of the incorporated drug is retained after 30 days storage in a methanol/water (3:1 v/v) mixture. In comparison with hydrocortisone, only a small quantity of testosterone is absorbed by the matrix.
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    Biomimetic growth of calcium phosphate over ATP coupled PMMA films
    (BIOCERAMICS 15, 2003) Yokogawa, Y; Varman, HK; Sreenivasan, K
    Biomimetic growth of calcium phosphate phase was studied over phosphate group functionalised polymethy methaerylate (PMMA) films using Fourier Transform Infrared Spectroscopy (FTIR), Electron Spectroscopy (ESCA), Scanning Electron Microscopy (SEM) and Energy Dispersive X ray Analysis(EDS). PMMA films were prepared by dissolving PMMA pellets in chloroform and cast into thin sheets. The films were immersed in a methanol solution of sodium hydroxide before treating with 1.5% solution of adenosine triphosphate (ATP) at a pH of 5.2 for 24 hours. The films were then soaked in saturated lime solution for 4 days to initiate formation of calcium phosphate precursor phase over their surface. The above films immersed in simulated body fluid solution (1.5 x SBF) for more than 5 days led to the nucleation of apatitic calcium phosphate phase over the film surface.
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    Calcium ion modulates protein release from chitosan-hyaluronic acid poly electrolyte gel
    (Poly. Eng. Sci., 2015-05) Krishna, AS; Radhakumary, C; Sreenivasan, K
    Polyelectrolyte complex (PEC) of chitosan (CH) and hyaluronic acid (HA) are widely used for skin, cartilage, and bone tissue engineering. However, no reports are seen on their response at high ionic media, like increased Ca21 where they are likely to be exposed in the form of bone constructs and the influence of these ions on modulating the release of incorporated entities such as drugs and growth factors. Here, we prepared freeze dried scaffolds of PEC of CH and HA (CH-HA) and characterized them by FTIR, TGA, SEM, and ESEM. FITC conjugated BSA, designated as FA, was incorporated into the PEC to study the release properties in response to Ca21. The swellability of CH-HA and the extent of drug release from the matrix, FA loaded CH-HA was studied in deionised water and aqueous Na1 and Ca21 solutions. Swelling and drug release were high for the matrix in aqueous Ca21 whereas it was remarkably low in water and Na1. Drug released was found to increase with concentrations of Ca21 (0.02–1.0M) indicating that CH-HA is a promising matrix for Ca21 responsive delivery of agents to accelerate healing of bone cracks, which is known to release high amount of Ca21.
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    Carbon dot based non enzymatic approach for the detection and estimation of glucose in blood serum
    (MATERIALS RESEARCH EXPRESS, 2016) Krishna, AS; Nair, PA; Radhakumary, C; Sreenivasan, K
    In this study we generated a simple, reliable and selective approach based on carbon dots (CDs) and 4-cyanophenylboronic acid (CPBA) for blood glucose sensing. The methodology relies on the quenching of the emission of CDs by CPBA followed by its recovery by glucose. The system consisting of CDs and CPBA was characterised by Fourier transform infra red spectrum, transmissions electron microscopic, dynamic light scattering instrument, UV-visible and fluorescence techniques. The response of the probe, CD-BA in presence of different concentrations of glucose was assessed. Linear range was obtained for glucose concentrations ranging from 1 to 30 mM. Interferences by other saccharides and various biomolecules coexisting in blood serum were negligible. The chemo sensor thus developed has been successfully used for the estimation of glucose in human blood serum. The system being sensitive, efficient and easy to perform is a promising platform for blood glucose sensing.
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    Conjugating Curcumin to Water Soluble Polymer Stabilized Gold Nanoparticles via pH Responsive Succinate Linker
    (J. Mater. Chem B., 2015-01) Dey, S; Sreenivasan, K
    Curcumin is a natural product with immense medicinal assets. The low aqueous solubility and consequent poor bioavailability of curcumin are the most serious limitations to its utilization as a potential therapeutic agent. In order to enhance the aqueous solubility and bioavailability of the drug, we covalently conjugated curcumin onto the surface of gold nanoparticles (AuNPs) aided by a water soluble polymer via a succinate linker. Conjugation of curcumin was confirmed by fluorescence, FTIR, 1H NMR and UV-Visible spectroscopy and XRD studies. The size and surface charge of the AuNPs were determined by DLS, and the morphology was visualized by TEM. Aqueous solubility of curcumin was augmented upon conjugation with the polymer stabilized AuNPs. The pH responsive release of curcumin from the nano-vehicle ensures safer delivery of the drug at physiological pH. Cytotoxic potential and cellular uptake of curcumin conjugated AuNPs were assessed by MTT assay and fluorescence microscopy, respectively, using C6 glioma cancer cells. Thus, the curcumin conjugated polymer stabilized AuNPs circumvent limitations of curcumin and can find applications in pH responsive drug delivery.