Browsing by Author "Moses, LR"

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    Beta cyclodextrin-insulin-encapsulated chitosan/alginate matrix: Oral delivery system
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2000) Moses, LR; Dileep, KJ; Sharma, CP
    Cyclodextrins (CD) form inclusion complexes with many drug molecules. The complexed drugs have increased bioabsorption in in vivo system. We have attempted to complex insulin with P-Cyclodextrin (BCD) and encapsulate in the chitosan/ calcium alginate matrix. For drug release studies insulin complexed with BCD for 20 min and that complexed with BCD for 150 min have been used for encapsulation in the chitosan/calcium alginate matrix. The two matrices seem to have different drug release profiles in simulated intestinal medium (pH 7.4) It appears that drug release from the 20-min BCD complexed system encapsulated in the chitosan/calcium alginate matrix begins only after an hour, where, being released from the 150-min BCD complexed system it begins in the first hour itself. Also, aggregation of the insulin molecules seems to be reduced by the complexation of the drug with BCD. Another noticeable fact is the change in the loading character, which is found to be inversely related to the concentration of BCD when it is above the stoichiometric equivalent of the drug. In an attempt to increase the payload of the drug in the matrix, the pH of the processing medium consisting of calcium chloride and chitosan is varied. It is found that the encapsulation efficiency increases as the pH is decreased from 6.0 to 4.0. Another way of increasing the loading is studied by decreasing the concentration gradient of insulin in the processing alginate solution and the crosslinking medium consisting of chitosan/calcium chloride. Preliminary animal studies on rabbits seem to be promising. (C) 2000 John Wiley & Sons, Inc.
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    Covalently bonded heparin to alter the pericardial calcification
    (ARTIFICIAL CELLS BLOOD SUBSTITUTES AND IMMOBILIZATION BIOTECHNOLOGY, 2000)
    Calcification is the leading cause of failure of a wide spectrum of cardiovascular and non-cardiovascular medical devices. In this study our aim was to immobilize polyethylene glycol (PEG) and heparin on multiple crosslinked bovine pericardium with Glutaraldehyde (GA) and carbodiimide. Grafting of PEG and heparin through an intermediate tissue bound substrate containing aldehyde and imide functional groups showed reduction in calcification. In this experimental protocol, we used Golomb and Wagner's in vitro model for studying pericardial calcification and a diffusion cell with two compartments for evaluating the diffusion of calcium across the BP. The results showed that heparin immobilization on the surface reduces calcification independent of its concentration in the incubating medium. It is conceivable that inactivation of unpaired aldehydic moieties present in pericardium after exposure to GA act as potential site for PEG grafting and imide functionalities of EDC can covalently bind heparin, would be the key step in the prevention of calcification It is well-established fact that heparin has a potent antithrombotic effect. But the exact role of heparin in the anticalcification process of bioprostheses still remain elusive.