title: Physicochemical characterization and enzymatic degradation of casein microcapsules prepared by aqueous coacervation.
abstract: The use of biopolymers in sustained release systems has been studied by many research groups because of the bioavailability and biodegradability of these compounds. Casein is a natural biopolymer whose degradation results in biologically utilisable compounds. The objective of the present study was to assess the potential of casein microcapsules (CAS/MC) as sustained release systems using acetaminophen as a model drug. CAS/MC were prepared by aqueous coacervation in lactate buffer containing gelatin, hydroxypropyl cellulose (HPC) and lecithin. After preparation, the microcapsules were treated, or not, with glutaraldehyde as a cross-linking agent. CAS/MC were loaded using two distinct procedures, either by dissolving 50% of the drug (w/w), relative to casein, in the polymer dispersion or by dissolving the drug in the coacervating solution. The drug present in CAS/MC was quantified by HPLC after an enzymatic degradation assay, and the CAS/MC were analysed by scanning electron microscopy and thermal analysis (differential scanning calorimetry and thermogravimetrical analysis). Loading of the drug was approximately 8% (w/w), with high resistance to enzymatic attack. The absence of an acetaminophen melting peak indicated that there was no drug present on the surface of the cross-linked systems. In addition, loading was accompanied by a reduction of the specific heat capacity of the systems, which suggests a decrease in stability. The outer morphology of the encapsulating polymer was affected by the process of microencapsulation. The data suggest that the microencapsulation process of aqueous coacervation and cross-linking is appropriate for the preparation of microencapsulated systems for sustained drug delivery.
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, 14040-903, Ribeirão Preto - SP, Brazil.
authors.forename: A J P
authors.initials: AJ
authors.lastname: Santinho
authors.forename: J M
authors.initials: JM
authors.lastname: Ueta
authors.forename: O
authors.initials: O
authors.lastname: Freitas
authors.forename: N L
authors.initials: NL
authors.lastname: Pereira
mesh_terms: D000082:Acetaminophen / Q000008:administration & dosage; D001673:Biodegradation, Environmental; D001704:Biopolymers; D002152:Calorimetry, Differential Scanning; D002214:Capsules / Q000737:chemistry / Q000493:pharmacokinetics; D002364:Caseins / Q000737:chemistry* / Q000493:pharmacokinetics; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003432:Cross-Linking Reagents; D003692:Delayed-Action Preparations; D010450:Endopeptidases / Q000378:metabolism; D066298:In Vitro Techniques; D008855:Microscopy, Electron, Scanning; D013818:Thermogravimetry; D014867:Water
chemical_list: D001704:Biopolymers; D002214:Capsules; D002364:Caseins; D003432:Cross-Linking Reagents; D003692:Delayed-Action Preparations; D014867:Water; D000082:Acetaminophen; D010450:Endopeptidases