Influence of Polyethylene Glycol Graftings on the in Vitro Degradation and Calcification of Bovine Pericardium

Vasudev, Sindhu C.; Chandy, Thomas; Sharma, Chandra P.

doi:10.1177/088532829701100403

Cited by 14 publications

(10 citation statements)

References 14 publications

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“…For that, 450 mg of hirudin-encapsulated alginate beads were exposed overnight to 2.5% glutaraldehyde vapors. They were further incubated in 5% solution of polyethylene glycol (PEG-20,000) in 0.1 M Tris-HCl buffer, pH 5.0 for 5 h. 26 The PEGgrafted samples were then washed with distilled water to remove the unattached PEGs, then were air dried.…”

Section: Microcapsule Formationmentioning

confidence: 99%

Chitosan/polyethylene glycol-alginate microcapsules for oral delivery of hirudin

Chandy

Mooradian

Rao

1998

J. Appl. Polym. Sci.

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ABSTRACT:A mild chitosan/calcium alginate microencapsulation process, as applied to encapsulation of biological macromolecules such as albumin and hirudin, was investigated. The polysaccharide chitosan was reacted with sodium alginate in the presence of calcium chloride to form microcapsules with a polyelectrolyte complex membrane. Hirudin-entrapped alginate beads were further surface coated with polyethylene glycol (PEG) via glutaraldehyde functionalities. It was observed that approximately 70% of the content is being released into Tris-HCl buffer, pH 7.4 within the initial 6 h and about 35% release of hirudin was also observed during treatment with 0.1 M HCl, pH 1.2 for 4 h. But acid-treated capsules had released almost all the entrapped hirudin into Tris-HCl, pH 7.4 media within 6 h. From scanning electron microscopic and swelling studies, it appears that the chitosan and PEG have modified the alginate microcapsules and subsequently the protein release. The microcapsules were also prepared by adding dropwise albumin-containing sodium alginate mixture into a PEG-CaCl 2 system. Increasing the PEG concentration resulted in a decrease rate of albumin release. The results indicate the possibility of modifying the formulation to obtain the desired controlled release of bioactive peptides (hirudin), for a convenient gastrointestinal tract delivery system.

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Section: Microcapsule Formationmentioning

confidence: 99%

Chitosan/polyethylene glycol-alginate microcapsules for oral delivery of hirudin

Chandy

Mooradian

Rao

1998

J. Appl. Polym. Sci.

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“…Nagaoka et al33 synthesized a graft copolymer of methacrylates with PEG and found the resulting polymer to be quite nonthrombogenic. Recent studies of Vasudev et al34–36 have demonstrated that the surface grafting of bovine pericardium through high molecular weight PEG via glutaraldehyde linkages can provide new ways of controlling tissue biodegradation, calcification, and thrombosis. Thus, these new microcapsules fabricated from PLA–PEG may serve to provide controlled taxol delivery and immunoprotection, whereas the outer layer of PEG may serve to enhance biocompatibility and reduce biodegradation.…”

Section: Discussionmentioning

confidence: 99%

Controlled delivery of taxol from poly(ethylene glycol)-coated poly(lactic acid) microspheres

Das

Rao

Wilson

et al. 2001

J. Biomed. Mater. Res.

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The development of injectable microspheres for sustained drug delivery to the arterial wall is a major challenge. We demonstrated the possibility of entrapping an antiproliferative agent, taxol, in poly(ethylene glycol) (PEG)-coated biodegradable poly(lactic acid) (PLA) microspheres with a mean diameter of 2-6 microm. A solution of taxol and PLA dissolved in an acetone/dichloromethane mixture was poured into an aqueous solution of PEG [or poly(vinyl alcohol) (PVA] with stirring with a high-speed homogenizer for the formation of microspheres. Taxol recovery in PLA-PEG microspheres was higher (61.2 +/- 2.3%) than with PVA-based (41.6 +/- 1.8%) preparations. An analysis by diffuse reflectance infrared Fourier transform spectroscopy revealed that PEG was incorporated well on the PLA microsphere surface. Scanning electron microscopy revealed that the PEG-coated PLA microspheres were spherical in shape and had a smooth surface texture like those of PVA-based preparations. The amount of drug release was much higher initially (25-30%); this was followed by a constant slow-release profile for a 30-day period of study. This PEG-coated PLA microsphere formulation may have potential for the targeted delivery of antiproliferative agents to treat restenosis.

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“…The calcium (CaCl 2 2H 2 O) and phosphate (K 2 H PO 4 ) solutions were prepared in 0.1 M Tris buffer (pH 7.4) containing 0.03% methyl 4‐hydroxy benzoate and 0.01% propyl 4‐hydroxy benzoate as preservatives. Equal volumes of doubled concentrations of 2.57 m M calcium and 1.54 m M phosphate were mixed in a screw cap bottle containing the pericardial tissues ( 11, 18). These solutions were also incorporated with a protein mixture containing 25 mg% albumin, 15 mg%γ‐globulin, and 7.5 mg% fibrinogen.…”

Section: Methodsmentioning

confidence: 99%

“…Two major approaches to reduce the calcification of tissue prostheses have been attempted. First, implant modification has been attempted to prevent calcification by precoating surfaces with various agents such as diphosphonates, sodium dodecyl sulphate, protamine sulphate, aluminum and ferric ions, or 2‐amino oleic acid ( 9, 10) or grafting polyethylene glycols ( 11, 12). Second, local polymeric delivery of some of these agents ( 13, 14) has been attempted.…”

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confidence: 99%

Changes in Pericardial Calcification Due to Antiplatelet Agents: In Vitro Studies

1998

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To develop tissue valves for prolonged use in the cardiovascular system, the complicated process of surface induced calcification must be better understood. Calcification was examined for 60 days on glutaraldehyde treated bovine pericardium (GABP) and enzyme extracted tissues fixed in glutaraldehyde (GATBP) incubated in metastable solutions of calcium phosphate, and the roles of aspirin and persantine in conjunction with vitamins C, B, or E, gentamycin (antibiotic), or pentothal sodium (anesthetic) in the medium were examined. Further, the diffusion of calcium across the GATBP was evaluated using a diffusion cell with 2 compartments. Pericardial calcification was also observed using scanning electron microscopy (SEM) techniques. It seems that the examined antiplatelet agents can modify the pericardial surfaces and subsequently their mineralization processes (GATBP, 31.7 micrograms/mg tissue; in the presence of 5 mg% vitamin C, 13.1 micrograms/mg tissue; in 1.5 mg% aspirin, 17.2 micrograms/mg tissue; and 1 mg% gentamycin, 14.8 micrograms/mg tissue) on exposure with the metastable calcium phosphate solution for 60 days. In addition, these agents may modify calcium transport and interfere with the adsorption at the surface, hence reducing calcium nodulation on GATBP. Scanning electron micrographs also revealed a reduction in calcium deposition on the pericardium due to these antiplatelet agents. It may be hypothesized that the influx of calcium on GATBP may be due to the cellular components or the involvement of plasma proteins like the fibrinogen molecule. The exact mechanism of these changes in the calcification of the pericardium are still unknown. From these in vitro findings, it appears that a combined vitamin therapy with low doses of aspirin may be beneficial for platelet suppression and thereby for prevention of thrombosis and calcification. However, more in vivo studies are needed to develop applications.

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Influence of Polyethylene Glycol Graftings on the in Vitro Degradation and Calcification of Bovine Pericardium

Cited by 14 publications

References 14 publications

Chitosan/polyethylene glycol-alginate microcapsules for oral delivery of hirudin

Chitosan/polyethylene glycol-alginate microcapsules for oral delivery of hirudin

Controlled delivery of taxol from poly(ethylene glycol)-coated poly(lactic acid) microspheres

Changes in Pericardial Calcification Due to Antiplatelet Agents: In Vitro Studies

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