| 1. |
- Gupta, Bhuvanesh, et al.
(författare)
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In vitro degradation of dry-jet-wet spun poly(lactic acid) monofilament and knitted scaffold
- 2007
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 103:3, s. 2006-2012
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Tidskriftsartikel (refereegranskat)abstract
- In vitro degradation behavior of dry-jet-wet spun poly(lactic acid) (PLA) monofilament and knitted scaffold were studied at three different pH i.e., at 4.6, 7.4, and 8.0 at 37°C for 20 weeks. Characterization of PLA by intrinsic viscosity, thermal properties, and scanning electron microscopy (SEM) was carried out. It is observed that the pH of the medium has significant role on degradation behavior of PLA. The degradation at pH 4.6 is observed to be maximum, which is confirmed by the drop of 52% in intrinsic viscosity. The degradation process has effect on the hydrophobicity of the PLA. The decrease in contact angle from 73° to 48° indicates that the PLA surface tends to become more hydrophilic as the degradation proceeds. The SEM analysis showed that with the degradation, surface deterioration takes place.
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| 2. |
- Gupta, Bhuvanesh, et al.
(författare)
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Poly(lactic acid) fiber : An overview
- 2007
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Ingår i: Progress in polymer science. - : Elsevier BV. - 0079-6700 .- 1873-1619. ; 32:4, s. 455-482
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Forskningsöversikt (refereegranskat)abstract
- Poly(lactic acid) (PLA) has generated great interest as one of the most innovative materials being developed for a wide range of applications. The polymer is thermoplastic and biodegradable, which makes it highly attractive for biological and medical applications. It can be transformed by spinning into filaments for subsequent fabrication of desirable textile structures. Spinning may be accomplished by various routes, each with its merits and demerits. The medical applications of this polymer arise from its biocompatibility: the degradation product, lactic acid, is metabolically innocuous. The fibers may be fabricated into various forms and may be used for implants and other surgical applications such as sutures. Tissue engineering is the most recent domain where poly(lactic acid) is being used and is found to be one of the most favorable matrix materials. The present article presents a critical review on the production of poly(lactic acid) fiber by various methods, along with correlations between structure and properties of the fibers. The applications of these fibers in various domains are also discussed.
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| 3. |
- Gupta, Bhuvanesh, et al.
(författare)
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Preparation of poly(lactic acid) fiber by dry-jet-wet spinning. II. Effect of process parameters on fiber properties
- 2006
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 101:6, s. 3774-3780
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Tidskriftsartikel (refereegranskat)abstract
- The dry-jet-wet spinning process was employed to spin poly(lactic acid)(PLA) fiber by the phase inversion technique using chloroform and methanol as solvent and nonsolvent, respectively, for PLA. The as spun fiber was subjected to two-stage hot drawing to study the effect of various process parameters, such as take-up speed, drawing temperature, and heat-setting temperature on the fiber structural properties. The take-up speed had a pronounced influence on the maximum draw ratio of the fiber. The optimum drawing temperature was observed to be 90°C to get a fiber with the tenacity of 0.6 GPa for the draw ratio of 8. The heat-setting temperature had a pronounced effect on fiber properties.
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| 4. |
- Gupta, Bhuvanesh, et al.
(författare)
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Radiation-induced graft modification of knitted poly(ethylene terephthalate) fabric for collagen immobilization
- 2007
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Ingår i: Polymers for Advanced Technologies. - : Wiley. - 1042-7147 .- 1099-1581. ; 18:4, s. 281-285
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Tidskriftsartikel (refereegranskat)abstract
- Radiation-induced graft co-polymerization of methacrylic acid and N-vinyl-2-pyrrolidone mixture from poly(ethylene terephthalate) knitted fabrics were conducted using a preirradiation method. The influence of the graft conditions, such as irradiation dose, reaction time, monomer concentration and temperature on the degree of grafting was determined. It was found that there is a limiting irradiation dose of 40 kGy above which the degree of grafting does not increase. An increase in the monomer concentration from 20 to 40% and an increase in temperature from 60 to 80°C gave a higher initial rate of grafting as well as higher equilibrium graft levels. The characterization of the fabric was carried out by attenuated total reflectance infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The grafted fabric surface, carrying negatively charged carboxylate ions, was shown to attract collagen, being positively charged to provide bioreceptive surfaces.
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| 5. |
- Gupta, Bhuvanesh, et al.
(författare)
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Surface modification of polycaprolactone monofilament by low pressure oxygen plasma
- 2013
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 127:3, s. 1744-1750
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Tidskriftsartikel (refereegranskat)abstract
- Surface modification of polycaprolactone filament has been carried out using a low pressure oxygen plasma to introduce active centers in the form of radicals, peroxides, and hydroperoxides on the surface. Evaluation by 2, 2-diphenyl-1-picrylhydrazyl method shows that there is an optimum value of exposure time, gas pressure, and discharge power for the generation of the maximum concentration of such groups. The plasma exposure time was thereafter varied to study the extent of the surface modification introduced by the plasma. It was found that only a short time of exposure to the oxygen plasma was necessary to make the surface highly wettable and polar with increased surface energy and work of adhesion. Surface chemical analysis by X-ray photoelectron spectroscopy revealed that this happens because of oxidation of the top layer of the filament, which occurs primarily by the breaking of bonds and incorporation of oxygen containing functionalities. Morphological and topographical observations by scanning electron microscopy and atomic force microscopy revealed that etching is pronounced at longer exposure times leading to a rougher surface with hill-valley features.
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| 6. |
- Hoogenkamp, Henk R., et al.
(författare)
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Seamless Vascularized Large-Diameter Tubular Collagen Scaffolds Reinforced with Polymer Knittings for Esophageal Regenerative Medicine
- 2014
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Ingår i: Tissue Engineering. Part C, Methods. - : Mary Ann Liebert Inc. - 1937-3384 .- 1937-3392. ; 20:5, s. 423-430
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Tidskriftsartikel (refereegranskat)abstract
- A clinical demand exists for alternatives to repair the esophagus in case of congenital defects, cancer, or trauma. A seamless biocompatible off-the-shelf large-diameter tubular scaffold, which is accessible for vascularization, could set the stage for regenerative medicine of the esophagus. The use of seamless scaffolds eliminates the error-prone tubularization step, which is necessary when emanating from flat scaffolds. In this study, we developed and characterized three different types of seamless tubular scaffolds, and evaluated in vivo tissue compatibility, including vascularization by omental wrapping. Scaffolds (luminal O approximate to 1.5cm) were constructed using freezing, lyophilizing, and cross-linking techniques and included (1) single-layered porous collagen scaffold, (2) dual-layered (porous+dense) collagen scaffold, and (3) hybrid scaffold (collagen+incorporated polycaprolacton knitting). The latter had an ultimate tensile strength comparable to a porcine esophagus. To induce rapid vascularization, scaffolds were implanted in the omentum of sheep using a wrapping technique. After 6 weeks of biocompatibility, vascularization, calcification, and hypoxia were evaluated using immunohistochemistry. Scaffolds were biocompatible, and cellular influx and ingrowth of blood vessels were observed throughout the whole scaffold. No calcification was observed, and slight hypoxic conditions were detected only in the direct vicinity of the polymer knitting. It is concluded that seamless large-diameter tubular collagen-based scaffolds can be constructed and vascularized in vivo. Such scaffolds provide novel tools for esophageal reconstruction.
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| 7. |
- Saxena, Shalini, et al.
(författare)
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Plasma-Induced Graft Polymerization of Acrylic Acid onto Poly(propylene) Monofilament : Characterization
- 2010
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Ingår i: Plasma Processes and Polymers. - : Wiley. - 1612-8850. ; 7:7, s. 610-618
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Tidskriftsartikel (refereegranskat)abstract
- Poly(propylene) (PP) filaments were functionalized by plasma-grafting of acrylic acid and the characterization of the grafted filaments was carried out using various techniques. XPS content which causes a decrease in the analysis showed an increase in the oxygenated contact angle decreased from 88 for virgin PP to 28 for the filament with the maximum graft level. The storage of the samples leads to the loss in hydrophilicity. The grafts do not lead to any crystalline changes in the filament structure; significant changes however occur on the surface of the filaments as a function of the degree of grafting.
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| 8. |
- Sun, Weilun, et al.
(författare)
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Improving the Cell Distribution in Collagen-Coated Poly-Caprolactone Knittings
- 2012
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Ingår i: TISSUE ENG PART C-ME. - : Mary Ann Liebert Inc. - 1937-3384. ; 18:10, s. 731-739
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Tidskriftsartikel (refereegranskat)abstract
- Adequate cellular in-growth into biomaterials is one of the fundamental requirements of scaffolds used in regenerative medicine. Type I collagen is the most commonly used material for soft tissue engineering, because it is nonimmunogenic and a highly porous network for cellular support can be produced. However, in general, adequate cell in-growth and cell seeding has been suboptimal. In this study we prepared collagen scaffolds of different collagen densities and investigated the cellular distribution. We also prepared a hybrid polymer-collagen scaffold to achieve an optimal cellular distribution as well as sufficient mechanical strength. Collagen scaffolds [ranging from 0.3% to 0.8% (w/v)] with and without a mechanically stable polymer knitting [polycaprolactone (PCL)] were prepared. The porous structure of collagen scaffolds was characterized using scanning electron microscopy and hematoxylin-eosin staining. The mechanical strength of hybrid scaffolds (collagen with or without PCL) was determined using tensile strength analysis. Cellular in-growth and interconnectivity were evaluated using fluorescent bead distribution and human bladder smooth muscle cells and human urothelium seeding. The lower density collagen scaffolds showed remarkably deeper cellular penetration and by combining it with PCL knitting the tensile strength was enhanced. This study indicated that a hybrid scaffold prepared from 0.4% collagen strengthened with knitting achieved the best cellular distribution.
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