Browsing by Author "Krishnan, V. Kalliyana"

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    The antithrombotic and antimicrobial properties of PEG-protected silver nanoparticle coated surfaces
    (BIOMATERIALS, 2012)
    Cardiovascular implant-associated complications such as infection and thrombosis may be reduced by modification of device surfaces using antimicrobial and antithrombotic agents. Silver nanoparticles (SNPs) are well accepted for its broad-spectrum antimicrobial effect. A recent report suggested its antiplatelet effect also. So the hypothesis of this study is that polyethylene glycol (PEG) protected SNPs can be incorporated with biomaterials to attain dual properties; and by adjusting an optimum concentration, its cytotoxicity to tissues and cells can be prevented. To prove this, detailed study of PEG-SNP was done at three levels: (i) direct inhibitory effect on platelet activation, aggregation and biochemical pathways when PEG-SNP is added into platelet suspension; (ii) inhibition of platelet adhesion to PEG-SNP incorporated biological matrix and polymer scaffold and (iii) non-cytotoxic behavior of immobilized PEG-SNP in fibrin matrix. Inhibitory effects demonstrated are on: platelet function by aggregometry, exposure of activation and apoptosis markers by flow cytometry, biochemical pathway by malondealdehyde (MDA) estimation and protein phosphorylation by Western blot. Reduced platelet adhesion onto PEG-SNP incorporated scaffold is shown using scanning electron microscopy (SEM). Non-toxic behavior of endothelial cells (EC) and smooth muscle cells (SMC) grown on PEG-SNP-fibrin disc is shown by fluorescence microscopy and cell phenotype stability by real-time polymerase chain reaction (PCR). (c) 2012 Elsevier Ltd. All rights reserved.
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    Vascular tissue construction on poly(e-caprolactone) scaffolds by dynamic endothelial cell seeding: effect of pore size
    (JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, 2012)
    In vitro tissue engineering for fabrication of small diameter vascular grafts probably undergoes a sequence of events similar to the in vivo angiogenesis process. In both cases endothelial cells (ECs) play the crucial role in generating a non-thrombogenic vessel lumen and stabilization of ECs in the lumen of new vessels requires the deposition of collagen IV and elastin. Shear stress is an important in vivo signal for inducing synthesis of extracellular matrix (ECM) components, collagen IV and elastin, which form the basement membrane in the case of new blood vessels. Stimulation of ECs may therefore produce collagen and elastin in the lumen of a polymeric scaffold during the vascular tissue-engineering process if appropriate biochemical and mechanical signals are presented. However, the morphology and physicochemical characteristics of polymer scaffolds may also be crucial for EC monolayer formation and ECM deposition. In this study, tubular scaffolds made of biodegradable poly(e-caprolactone) (PCL) with biomimetic fibrin-based coating were evaluated to compare the effects of pore sizes on surface coverage of ECs and synthesis of ECM under dynamic culture conditions. Actin was stained for identification of cells, while specific antibodies were used for locating collagen IV and elastin deposition on the scaffolds. It was found that dynamic seeding of ECs in the lumen stabilized the cells and aligned them along the direction of flow, with better deposition of insoluble elastin and collagen IV when similar to 75% of pores were < 24 mu m in diameter. In addition, monolayer on the e-PCL scaffolds with lower pore sizes was found to produce nitric oxide (NO), indicating a non-thrombogenic EC layer in the lumen. Copyright (c) 2011 John Wiley & Sons, Ltd.