Vidya Raj

Sree Chitra Tirunal Institute for Medical Sciences and Technology, Tiruvananantapuram, Kerala, India

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Publications (8)17.59 Total impact

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    ABSTRACT: Functionalized colloidal gold is widely used for qualitative and quantitative detection of specific analytes. We report here a novel modification of gold nanoparticles by digitonin, a glycoside used for precipitating membrane cholesterol. The specific molecular recognition of cholesterol by digitonin gold nanoparticles (DGNP), make it an attractive alternative to the existing enzymatic methods for cholesterol sensing. To enable cholesterol binding, we modified mercapto modified GNPs with digitonin, by a simple esterification reaction. The blue shift in the plasmon absorption spectra of DGNP with different cholesterol concentrations accompanied by a decrease in the absorbance is the principle applied here for the estimation. The observed size reduction followed by cholesterol binding is reasoned due to the enhanced hydophobicity of the surface which in turn expels the water layers associated with the particles prior to cholesterol binding. The method exhibited linearity between concentration of cholesterol and the corresponding absorbance of the plasmon peak, in the range of 160-600 ng/mL with a detection limit of 100±9 ng/mL. Other steroids did not show any binding affinity towards DGNP. The method depicted here has potential for development as an enzyme free sensor for cholesterol although many factors need to be addressed to transform it for assaying samples like blood.
    Biosensors & bioelectronics 09/2011; 27(1):197-200. · 5.43 Impact Factor
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    ABSTRACT: Scaffold free tissue constructs are preferred in tissue engineering as they overcome all the problems associated with scaffolds. Stimuli responsive polymers enable generation of scaffold free multilayered tissue constructs which would in turn reduce the use of biomaterials in vivo. In this study, we investigated cytocompatibility and thermoresponsiveness of a copolymer of N-Isopropylacrylamide and Methyl Methacrylate. Thermoresponsive surfaces were prepared by coating tissue culture polystyrene with the copolymer solution in isopropanol. Mammalian fibroblast cells (L929 cells) readily adhered on the copolymer. The viability and cellular activity was ensured through Neutral red staining, MTT assay, Tritiated thymidine uptake assay and Immunofluorescent staining for cytoskeletal organisation. Incubation under lower critical solution temperature of copolymer resulted in intact detachment of cells. To conclude, in-house synthesized cytocompatible smart culture substrate intended for tissue engineering was developed using a cost effective and simple technique. Moreover, presence of methyl methacrylate in the copolymer reduced the lower critical solution temperature facilitating extended in vitro manipulation time. As the copolymer is insoluble in water, the copolymer could be polymerised without additional crosslinkers.
    Journal of Materials Science Materials in Medicine 05/2010; 21(5):1631-9. · 2.14 Impact Factor
  • Vidya Raj, K Sreenivasan
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    ABSTRACT: A new method for the detection of C-reactive protein (CRP) in serum using functionalized gold nano-particles (GNP) is reported. The affinity towards CRP is imparted to GNP by tethering O-phosphorylethanolamine (PEA) onto their surface. GNP and modified GNP were characterized using TEM, particle size analysis, zeta potential measurements, absorption spectroscopy and FT-IR techniques. The event of binding of CRP onto the PEA-GNP is followed by visibly observable colour change. We observed a red shift as well as a decrease in absorption in the plasmon peak of the modified GNP with the concentration of CRP. When the concentration of CRP exceeded 450 ng mL(-1), particles were aggregated and the solution became turbid. The method exhibited a linear range for CRP from 50 to 450 ng mL(-1) with a detection limit of 50 ng mL(-1). The colour change and the variation in absorption of the GNP were highly specific to CRP even in the presence of albumin. We estimated CRP in blood serum collected from patients and the results obtained compared well with the estimation using the technique of nephelometry based on the antibody-antigen interaction.
    Analytica chimica acta 03/2010; 662(2):186-92. · 4.31 Impact Factor
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    ABSTRACT: 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°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. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
    Journal of Applied Polymer Science 01/2010; 115(1):52 - 62. · 1.40 Impact Factor
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    ABSTRACT: 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.
    Journal of Bioactive and Compatible Polymers - J BIOACT COMPAT POLYM. 01/2010; 25(1):58-74.
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    ABSTRACT: A new method without employing antibody for the estimation of C-reactive protein (CRP) in serum is presented. The method centres on the variation of fluorescence intensity of pair copolymers, containing a fluorophore (Fluoreseinamine isomer 1) and O-Phosphorylethanolamine (PEA), a ligand of CRP. We found that the fluorescence of fluorophore attached copolymer was quenched in the presence of copolymer conjugated with PEA. The fluorescence emission was, however, increased when CRP was added into the solution of the copolymers. The intensity of fluorescence increased linearly up to a concentration of 250ng/mL of CRP and then attained a constant value which remains the same with additional quantity of CRP. This observation was assigned to the saturation of the binding sites. Other proteins namely, albumin, fibrinogen and globulin did not show any interference in the measurement. The method was used for the estimation of CRP in blood serum of patients reported to the cardiology and the data compared well with the quantity of CRP in the same samples estimated using immunoassay method. Our results suggest that the polymer pick up CRP selectively from a complex milieu like serum. The method is simple, cost effective and sensitive with a detection limit of 20ng/mL.
    Sensors and Actuators B-chemical - SENSOR ACTUATOR B-CHEM. 01/2010; 146(1):23-27.
  • Vidya Raj, P R Hari, K Sreenivasan
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    ABSTRACT: Fluorescence intensity of N-isopropylacrylamide-glycidyl methacrylate (NIPAAm-GMA) copolymer conjugated with fluoreseinamine isomer1 was found to decrease considerably in the presence of NIPAAm-GMA copolymer containing O-phosphorylethanolamine (PEA), the specific ligand of C-reactive protein (CRP). The decrease in the emission intensity was reasoned due to the quenching of the fluorescence through the interaction of the polymer chains. The emission intensity was, however, found to increase rapidly when CRP was added in to the solution containing the polymers. The intensity of fluorescence emission was increased by five-fold in the presence of CRP as low as 20 ng mL(-1). Albumin, the major blood protein, did not show any interference in the emission. The presence of a low molecular protein, cytochrome c, on the fluorescence spectra was also studied and this protein also found not have any influence in binding of CRP onto the ligand indicating that other proteins irrespective of their molecular weights did not influence the measurement. A definite correlation was found between the concentration of CRP and the fluorescence intensity. The method appears to be very sensitive and easy to perform. The study reflects, for the first time, the scope of using copolymeric combinations for the measurement of CRP without the use of antibody.
    Analytica chimica acta 06/2007; 592(1):45-50. · 4.31 Impact Factor
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    ABSTRACT: Phosphorylethanolamine (PEA), C-reactive protein (CRP) specific ligand was coupled onto the surface of polymethyl methacrylate (PMMA) surface. Initially PMMA surface was modified by grafting glycidyl methacrylate (GMA). The anchoring of PEA on to PMMA was achieved through the ring opening reaction of epoxide group of GMA. The modified surface was characterized using FT-IR, scanning electron microscopy, energy dispersive X-ray analysis and contact angle measurement. The modified surface was found to bind CRP. The adsorbed protein was visualized by staining Coomassie blue. The quantification of the extent of adsorption was carried out using spectrophotometric measurement. The methodology appears to be simple and expandable further for the development of a sensing element for CRP.
    Sensors and Actuators B-chemical - SENSOR ACTUATOR B-CHEM. 01/2007; 127(2):330-334.