Browsing by Author "Columbus, S"

Now showing 1 - 6 of 6
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    Modulating Poly(epsilon-caprolactone) Scaffold Properties by Altering Porogen Concentration for Blood-Vessel Tissue Engineering
    (JOURNAL OF BIOMATERIALS AND TISSUE ENGINEERING, 2014) Columbus, S; Krishnan, LK; Krishnan, VK
    Achievement of optimum scaffold porosity while bearing relevant mechanical integrity and suitable degradation profile needs to be addressed appropriately for the successful construction of a tissue engineered blood vessel. Poly[ethylene glycol] (PEG) was used as porogen while fabricating poly[epsilon-caprolactone] (PCL) tubular scaffolds by solvent casting and particulate leaching process. Scaffolds were fabricated by varying polymer/porogen ratio from 4:1, 2:1, 4:3 and 1:1 for comparative study. The effect of porogen concentration on scaffold physico-chemical properties including real time degradation in PBS at 37 degrees C was studied using two reference molecular weight PEGs (3400 and 8000). Wall thickness and tubular consistency of cast scaffolds were found to improve with increasing PEG content. Analysis using micro-computed tomography (mu-CT) revealed majority of pores to lie between 12-24 mu m in size. The concentration of PEG was found to influence porosity, hydrophilicity, crystallinity and mechanical strength within scaffold systems containing each MW PEGs. Though considerable reduction in tensile strength was observed for scaffolds with 1:1 PCL:PEG ratio, mechanical integrity of these scaffolds were retained even after one year degradation. Scaffolds with 1:1 PEG-PCL ratio were found to have better structural integrity, highest porosity, favourable mechanical strength for blood vessel construction, long term degradation characteristics suitable for implant applications and good endothelial cell coverage after 3 days static cell culture.
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    Modulating Poly(ε-caprolactone) Scaffold Properties by Altering Porogen Concentration for Blood-Vessel Tissue Engineering
    (Journal of Biomaterials and Tissue Engineering, 2014-06) Columbus, S; Krishnan, LK; Krishnan, VK
    Achievement of optimum scaffold porosity while bearing relevant mechanical integrity and suitable degradation profile needs to be addressed appropriately for the successful construction of a tissue engineered blood vessel. Poly[ethylene glycol] (PEG) was used as porogen while fabricating poly[ε-caprolactone] (PCL) tubular scaffolds by solvent casting and particulate leaching process. Scaffolds were fabricated by varying polymer/porogen ratio from 4:1, 2:1, 4:3 and 1:1 for comparative study. The effect of porogen concentration on scaffold physico-chemical properties including real time degradation in PBS at 37 °C was studied using two reference molecular weight PEGs (3400 and 8000). Wall thickness and tubular consistency of cast scaffolds were found to improve with increasing PEG content. Analysis using micro-computed tomography (μ-CT) revealed majority of pores to lie between 12–24 μm in size. The concentration of PEG was found to influence porosity, hydrophilicity, crystallinity and mechanical strength within scaffold systems containing each MW PEGs. Though considerable reduction in tensile strength was observed for scaffolds with 1:1 PCL:PEG ratio, mechanical integrity of these scaffolds were retained even after one year degradation. Scaffolds with 1:1 PEG-PCL ratio were found to have better structural integrity, highest porosity, favourable mechanical strength for blood vessel construction, long term degradation characteristics suitable for implant applications and good endothelial cell coverage after 3 days static cell culture.
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    Potential of Tissue Engineered Blood Vessel as Model to Study Effect of Flow and Wall Thickness on Cellular Communication
    (Current Tissue Engineering., 2015-04) Ragaseema, VM; Columbus, S; Ramesh, R; Krishnan, LK
    In physiology, blood vessel function is maintained mainly through nitric oxide (NO)-mediated cross-talk between endothelial cells (ECs) and smooth muscle cells (SMCs), which is compromised in pathology. Lack of an appropriate in vitro model hampers the study of vascular disease progression mechanisms. This study attempted to use tissue engineered blood vessel (TEBV) as a model system to understand the effect of wall thickness and shear stress on EC to SMC communication. Differentiated ECs and SMCs obtained by in vitro culture of sheep peripheral blood mononuclear cells (PBMNCs) were seeded on biodegradable €-polycaprolactone (PCL) conduits of different wall thicknesses and exposed to shear stress in a two-channel bioreactor to construct functional TEBV. Phenotypes of ECs and SMCs were studied in terms of nitric oxide synthase (eNOS) and basic calponin expressions respectively, using real time polymerase chain reaction. Endothelial to SMC cross-talk under the influence of wall thickness and shear stress was interrelated to NO and cyclic GMP (cGMP) production. Shear stress accelerates, but wall thickness has no influence on endothelial NO production. Increased release of NO in response to shear stress resulted in augmented cGMP production, but only when the wall thickness was lower. Both wall thickness and shear stress affect cGMP production and smooth muscle contractile phenotype. From this study, it is also suggested that TEBV may be a suitable model to study various risk factors on vessel integrity
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    Relating pore size variation of poly (e-caprolactone) scaffolds to molecular weight of porogen and evaluation of scaffold properties after degradation
    (JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS, 2014) Columbus, S; Krishnan, LK; Krishnan, VK
    The major challenge in designing a scaffold for fabricating tissue engineered blood vessels is optimization of its microstructure for supporting uniform cellular in-growth with good mechanical integrity and degradation kinetics suitable for long-term implantation. In this study, we have investigated the feasibility of varying the pore size of poly(e-caprolactone) (PCL) scaffold by altering the molecular weight of porogen and studied the effect of degradation on morphological characteristics and mechanical properties of scaffolds by correlating to the extent of degradation. Scaffolds with two different pore sizes were prepared by solvent casting and particulate leaching where poly(ethylene glycol) (PEG) porogens having two molecular weights (3400 and 8000) were used and subjected to in vitro degradation in phosphate buffered saline (PBS) upto six months. Microcomputed tomography studies of scaffolds revealed narrower pore size distribution when PEG-3400 was used as porogen and had 78% pores in the 12-24 mu range, whereas incorporation of PEG-8000 resulted in broader distribution with only 65% pores in the same range. Degradation resulted in scaffolds with narrower pore size distribution to have better retention of morphological and mechanical characteristics compared to scaffolds with broader distribution. Gravimetric and molecular weight studies also showed that scaffold degradation in both cases was only in initial stages after 6 months and PCL scaffolds had potential to be recommended for vascular tissue engineering applications. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 789-796, 2014.
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    Relating pore size variation of poly (epsilon-caprolactone) scaffolds to molecular weight of porogen and evaluation of scaffold properties after degradation
    (Journal of Biomedical Materials Research part B: Applied Biomaterials., 2014-10) Columbus, S; Krishnan, LK; Krishnan, VK
    The major challenge in designing a scaffold for fabricating tissue engineered blood vessels is optimization of its microstructure for supporting uniform cellular in-growth with good mechanical integrity and degradation kinetics suitable for long-term implantation. In this study, we have investigated the feasibility of varying the pore size of poly(ɛ-caprolactone) (PCL) scaffold by altering the molecular weight of porogen and studied the effect of degradation on morphological characteristics and mechanical properties of scaffolds by correlating to the extent of degradation. Scaffolds with two different pore sizes were prepared by solvent casting and particulate leaching where poly(ethylene glycol) (PEG) porogens having two molecular weights (3400 and 8000) were used and subjected to in vitro degradation in phosphate buffered saline (PBS) upto six months. Microcomputed tomography studies of scaffolds revealed narrower pore size distribution when PEG-3400 was used as porogen and had 78% pores in the 12-24 µ range, whereas incorporation of PEG-8000 resulted in broader distribution with only 65% pores in the same range. Degradation resulted in scaffolds with narrower pore size distribution to have better retention of morphological and mechanical characteristics compared to scaffolds with broader distribution. Gravimetric and molecular weight studies also showed that scaffold degradation in both cases was only in initial stages after 6 months and PCL scaffolds had potential to be recommended for vascular tissue engineering applications.