Document Detail

Evaluation of the diffusion coefficient for controlled release of oxytetracycline from alginate/chitosan/poly(ethylene glycol) microbeads in simulated gastrointestinal environments.
MedLine Citation:
PMID:  15281914     Owner:  NLM     Status:  MEDLINE    
Diffusion studies of OTC (oxytetracycline) entrapped in microbeads of calcium alginate, calcium alginate coacervated with chitosan (of high, medium and low viscosity) and calcium alginate coacervated with chitosan of low viscosity, covered with PEG [poly(ethylene glycol) of molecular mass 2, 4.6 and 10 kDa, were carried out at 37+/-0.5 degrees C, in pH 7.4 and pH 1.2 buffer solutions - conditions similar to those found in the gastrointestinal system. The diffusion coefficient, or diffusivity (D), of OTC was calculated by equations provided by Crank [(1975) Mathematics in Diffusion, p. 85, Clarendon Press, Oxford] for diffusion, which follows Fick's [(1855) Ann. Physik (Leipzig) 170, 59] second law, considering the diffusion from the inner parts to the surface of the microbeads. The least-squares and the Newton-Raphson [Carnahan, Luther and Wilkes (1969) Applied Numerical Methods, p. 319, John Wiley & Sons, New York] methods were used to obtain the diffusion coefficients. The microbead swelling at pH 7.4 and OTC diffusion is classically Fickian, suggesting that the OTC transport, in this case, is controlled by the exchange rates of free water and relaxation of calcium alginate chains. In case of acid media, it was observed that the phenomenon did not follow Fick's law, owing, probably, to the high solubility of the OTC in this environment. It was possible to modulate the release rate of OTC in several types of microbeads. The presence of cracks formed during the process of drying the microbeads was observed by scanning electron microscopy.
Maria C Pinto Cruz; Sergio P Ravagnani; Fabio M S Brogna; Sérgio P Campana; Galo Cardenas Triviño; Antonio C Luz Lisboa; Lucia H Innocentini Mei
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Publication Detail:
Type:  Comparative Study; Evaluation Studies; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biotechnology and applied biochemistry     Volume:  40     ISSN:  0885-4513     ISO Abbreviation:  Biotechnol. Appl. Biochem.     Publication Date:  2004 Dec 
Date Detail:
Created Date:  2004-11-19     Completed Date:  2005-05-11     Revised Date:  2007-03-21    
Medline Journal Info:
Nlm Unique ID:  8609465     Medline TA:  Biotechnol Appl Biochem     Country:  England    
Other Details:
Languages:  eng     Pagination:  243-53     Citation Subset:  IM    
Universidade Estadual de Campinas, Faculdade de Engenharia Química, Departamento de Tecnologia de Polímeros, Caixa Postal 6066, CEP 13081-970, Campinas-SP, Brazil.
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MeSH Terms
Alginates / chemistry*
Anti-Bacterial Agents / administration & dosage,  chemistry
Chitosan / chemistry*
Coated Materials, Biocompatible / chemistry
Computer Simulation
Delayed-Action Preparations / chemistry*
Drug Carriers / chemistry
Gastrointestinal Contents / chemistry*
Glucuronic Acid / chemistry*
Hexuronic Acids / chemistry*
Materials Testing
Models, Chemical
Oxytetracycline / administration & dosage*,  chemistry*
Polyethylene Glycols / chemistry*
Reg. No./Substance:
0/Alginates; 0/Anti-Bacterial Agents; 0/Coated Materials, Biocompatible; 0/Delayed-Action Preparations; 0/Drug Carriers; 0/Hexuronic Acids; 0/Polyethylene Glycols; 576-37-4/Glucuronic Acid; 79-57-2/Oxytetracycline; 9005-32-7/alginic acid; 9012-76-4/Chitosan

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