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dc.typeArtigo de periódicopt_BR
dc.titleEvaluation Of The Diffusion Coefficient For Controlled Release Of Oxytetracycline From Alginate/chitosan/poly(ethylene Glycol) Microbeads In Simulated Gastrointestinal Environments.pt_BR
dc.contributor.authorCruz, Maria C Pintopt_BR
dc.contributor.authorRavagnani, Sergio Ppt_BR
dc.contributor.authorBrogna, Fabio M Spt_BR
dc.contributor.authorCampana, Sérgio Ppt_BR
dc.contributor.authorTriviño, Galo Cardenaspt_BR
dc.contributor.authorLisboa, Antonio C Luzpt_BR
dc.contributor.authorMei, Lucia H Innocentinipt_BR
unicamp.authorMaria C Pinto Cruz, Universidade Estadual de Campinas, Faculdade de Engenharia Química, Departamento de Tecnologia de Polímeros, Caixa Postal 6066, CEP 13081-970, Campinas-SP, Brazil.pt_BR P Ravagnani,pt M S Brogna,ptérgio P Campana,pt Cardenas Triviño,pt C Luz Lisboa,pt H Innocentini Mei,pt
dc.subjectAnti-bacterial Agentspt_BR
dc.subjectCoated Materials, Biocompatiblept_BR
dc.subjectComputer Simulationpt_BR
dc.subjectDelayed-action Preparationspt_BR
dc.subjectDrug Carrierspt_BR
dc.subjectGastrointestinal Contentspt_BR
dc.subjectGlucuronic Acidpt_BR
dc.subjectHexuronic Acidspt_BR
dc.subjectMaterials Testingpt_BR
dc.subjectModels, Chemicalpt_BR
dc.subjectPolyethylene Glycolspt_BR
dc.description.abstractDiffusion 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.en
dc.relation.ispartofBiotechnology And Applied Biochemistrypt_BR
dc.relation.ispartofabbreviationBiotechnol. Appl. Biochem.pt_BR
dc.identifier.citationBiotechnology And Applied Biochemistry. v. 40, n. Pt 3, p. 243-53, 2004-Dec.pt_BR
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