Browsing by Author "John, A"

Now showing 1 - 20 of 62
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    A functional hydrogel for regeneration of nucleus pulposus
    (JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, 2014) Roudmiane, MM; Babu, S; Varma, HK; John, A
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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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    An aqueous method for the controlled manganese (Mn2+) substitution in superparamagnetic iron oxide nanoparticles for contrast enhancement in MRI
    (PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 2015) Beeran, AE; Nazeer, SS; Fernandez, FB; Muvvala, KS; Wunderlich, W; Anil, S; Vellappally, S; Rao, MSR; John, A; Jayasree, RS; Varma, PRH
    Despite the success in the use of superparamagnetic iron oxide nanoparticles (SPION) for various scientific applications, its potential in biomedical fields has not been exploited to its full potential. In this context, an in situ substitution of Mn2+ was performed in SPION and a series of ferrite particles, MnxFe1-xFe2O4 with a varying molar ratio of Mn2+ : Fe2+ where 'x' varies from 0-0.75. The ferrite particles obtained were further studied in MRI contrast applications and showed appreciable enhancement in their MRI contrast properties. Manganese substituted ferrite nanocrystals (MnIOs) were synthesized using a novel, one-step aqueous co-precipitation method based on the use of a combination of sodium hydroxide and trisodium citrate (TSC). This approach yielded the formation of highly crystalline, superparamagnetic MnIOs with good control over their size and bivalent Mn ion crystal substitution. The presence of a TSC hydrophilic layer on the surface facilitated easy dispersion of the materials in an aqueous media. Primary characterizations such as structural, chemical and magnetic properties demonstrated the successful formation of manganese substituted ferrite. More significantly, the MRI relaxivity of the MnIOs improved fourfold when compared to SPION crystals imparting high potential for use as an MRI contrast agent. Further, the cytocompatibility and blood compatibility evaluations demonstrated excellent cell morphological integrity even at high concentrations of nanoparticles supporting the non-toxic nature of nanoparticles. These results open new horizons for the design of biocompatible water dispersible ferrite nanoparticles with good relaxivity properties via a versatile and easily scalable co-precipitation route.
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    Biodegradation and cytocompatibility studies of a triphasic ceramic coated porous hydroxyapatite for bone substitute applications
    (International Journal of Applied Ceramic Technology, 2008) John, A; Nair, MB; Varma, HK; Bernhardt, A; Gelinsky, M
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    Biodegradation and cytocompatibility studies of a triphasic ceramic-coated porous hydroxyapatite for bone substitute applications
    (INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, 2008) John, A; Nair, MB; Varma, HK; Bernhardt, A; Gelinsky, M
    Bone defects due to trauma or disease have led to the need for biomaterials as substitutes for tissue regeneration and repair. Herein, we introduce a porous triphasic ceramic-coated hydroxyapatite scaffold (HASi) for such applications. Interestingly, in the degradation experiments with isotonic buffer, HASi showed a significant release of silica with the disappearance of the tricalcium phosphate phase. Furthermore, the material also exhibited cytocompatibility with cultured bone marrow-derived mesenchymal stem cells of human origin. The material chemistry, together with the favorable cellular characteristics, indicates HASi as a promising candidate for critical-size bony defects, which still remains a formidable clinical challenge in the orthopedic scenario.
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    Biokinetics and In Vivo Distribution Behaviours of Silica-Coated Cadmium Selenide Quantum Dots
    (BIOLOGICAL TRACE ELEMENT RESEARCH, 2011) Vibin, M; Vinayakan, R; John, A; Raji, V; Rejiya, CS; Abraham, A
    Recently, quantum dots derived from trace elements like cadmium and selenium have attracted widespread interest in biology and medicine. They are rapidly being used as novel tools for both diagnostic and therapeutic purposes. In this report, we evaluated the distribution of silica-coated cadmium selenide (CdSe) quantum dots (QDs) following intravenous injection into male Swiss albino mice as a model system for determining tissue localization using in vivo fluorescence and ex vivo elemental analysis by inductively coupled plasma optical emission spectroscopy (ICP-OES). Trioctylphosphine oxide-capped CdSe quantum dots were synthesized and rendered water soluble by overcoating with silica, using aminopropyl silane (APS) as silica precursor. ICP-OES was used to measure the cadmium content to indicate the concentration of QDs in blood, organs and excretion samples collected at predetermined time intervals. Meanwhile, the distribution and aggregation state of QDs in tissues were also investigated in cryosections of the organs by fluorescence microscopy. We have demonstrated that the liver and kidney were the main target organs for QDs. Our systematic investigation clearly shows that most of the QDs were metabolized in the liver and excreted via faeces and urine in vivo. A fraction of free QDs, maintaining their original form, could be filtered by glomerular capillaries and excreted via urine as small molecules within 5 days.
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    Bone growth response with porous hydroxyapatite granules in a critical sized lapine tibial-defect model
    (Bulletin of Materials Science., 2002) John, A; Abiraman, S; Varma, HK; Kumar, TV; Umashankar, PR
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    Cell interaction studies with novel Bioglass coated Hydroxyapatite porous blocks
    (Trends in Biomaterials & Artificial Organs., 2006) Nair, MB; Varma, HK; Kumary, TV; Babu, SS; John, A
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    Cellular uptake and subcellular localization of highly luminescent silica-coated CdSe quantum dots - In vitro and in vivo
    (JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2011) Vibin, M; Vinayakan, R; John, A; Rejiya, CS; Raji, V; Abraham, A
    With excellent optical properties, quantum dots (QDs) have been made as attractive molecular probes for labeling cells in biological research. The purpose of the present work is to explore the possible role of silica-coated cadmium selenide (CdSe) QDs in the in vitro and in vivo cellular uptake and their subcellular localization. The in vitro uptake characteristics of silica-coated CdSe QDs were performed in cultured New Zealand rabbit adipose tissue-derived mesenchymal stem cells (RADMSCs) and Human cervical cancer cells (HeLa) using fluorescence microscopy after staining with 4,6-diamidino-2-phenylindole (DAPI). The in vitro results showed that the silica-coated CdSe QDs were efficiently taken up by the cells and it was localized in the intracellular vesicles giving strong fluorescence from the cytoplasm and nearby nucleus. Subsequently, the in vivo localization and distribution of QDs were studied by the hematoxilin stained semithin cryosections of tissues (similar to 15 mu m thickness) under fluorescence microscopy and ultrathin sections of tissues (similar to 100 nm thickness) under confocal laser scanning microscopy at the distribution maxima. Our in vivo results confirmed the effective cellular uptake and even distribution pattern of QDs in tissues. Overall, these in vitro and in vivo results are represented with focus on internalization, subcellular localization and distribution of the QDs, in view of their potential applications in biomedical field. (C) 2011 Elsevier Inc. All rights reserved.
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    Characterisation of novel bioactive glass coated hydroxyapatite granules in correlation with in vitro and in vivo studies
    (Trends in Biomaterials & Artificial Organs., 2006) Sandeep, G; Varma, HK; Kumary, TV; Babu, SS; John, A
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    Cyclic RGD Peptide Conjugated Trypsin Etched Gold Quantum Clusters: Novel Biolabeling Agents for Stem Cell Imaging
    (Journal of Stem Cells., 2012) Das, B; Fernandez, FB; John, A; Sharma, CP
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    Cytocompatibility Studies of a Novel Bioactive Glass Coated Porous Hydroxyapatite Bioceramic for Use as a Bone Substitute
    (Key Engineering Materials., 2005) John, A; Varma, HK; Kumari, TV; Nisha, VR; Narayanan, D
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    Cytotoxicity and fluorescence studies of silica-coated CdSe quantum dots for bioimaging applications
    (Journal of Nanoparticle Research., 2011) Vibin, M; Vinayakan, R; John, A; Raji, V; Rejiya, CS; Abraham, A
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    Effect of Ultrasound exposure on mouse calvaria 3T3-E1 cells
    (Biomedical Engineering: Applications, Basis and Communications., 2000) John, A; Ikada, Y; Tabata, Y
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    Effect of ZR 515, Methoprene (Jha) on Castor Semilooper Larvae of Achaea janata (L) (Lepidoptera-Noctuidae)
    (Indian Journal of Experimental Biology., 1993) John, A; Muraleedharan, D
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    Effective cellular internalization of silica-coated CdSe quantum dots for high contrast cancer imaging and labeling applications.
    (Cancer Nanotechnology., 2015-01) Vibin, M; Vinayakan, R; John, A; Fernandez, FB; Abraham, A
    The possibility of developing novel contrast imaging agents for cancer cellular labelling and fluorescence imaging applications were explored using silica-coated cadmium selenide (CdSe) quantum dots (QDs). The time dependent cellular internalization efficiency study was carried out using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Confocal Laser Scanning Microscopy (cLSM) after exposing QDs to stem cells and cancer cells. The strong fluorescence from the cytoplasm confirmed that the QDs were efficiently internalized by the cells. The internalization maxima were observed at the fourth hour of incubation in both stem and cancer cells. Further, the in vitro fluorescence imaging as well as localization study of QDs were performed in various cells. Moreover, high contrast in vivo tumor imaging efficiency of silica-coated CdSe QDs was performed in ultrathin sections of tumor mice, and the results confirmed its effective role in cellular imaging and labelling in cancer and other diseases.
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    Fibrin glue as an osteoinductive protein in a mouse model
    (BIOMATERIALS, 2002)
    Fibrin sealant or fibrin glue (FG) has been found to be effective as a wound-healing substance in surgery. However, its role in bone fracture healing and osseous tissue response is not fully understood. This ambiguity questions the potential of FG as an inductive protein. The present study was undertaken to evaluate the osteoinductive property of FG when coated with calcium phosphate and glass ceramics and implanted in the extraskeletal site of male Swiss albino mice. Implant materials used for this study were hydroxyapatite (HA) porous granules (300-350 mum), bioactive glass system (BGS)-AW type and calcium phosphate calcium silicate system (HABGS) non-porous granules (300-350 mum). Uncoated granules (control) and coated granules with 2.5 mg FG and 5 mg FG were implanted in the quadriceps muscle of mice and sacrificed after 28 days. Histologically, HA, BGS and HABGS implanted animal groups showed good healing response. However, neo-osteogenesis was observed only in the BGS and HABGS granules impregnated with FG. Furthermore, bone formation was observed to be more conspicuous in 5 mg FG coated BGS and HABGS granules when compared with 2.5 mg FG coated BGS and HABGS granules. Fluorochrome labeling proved that mineralization had already started by day 15 with FG preadsorbed BGS and HABGS granules. On the contrary, the uncoated granules did not show any de novo bone formation. This experimental study provides an evidence of the positive role of FG as a potential osteoinductive biologic tissue adhesive. (C) 2002 Elsevier Science Ltd. All rights reserved.