Santinho A J P, Ueta J M, Freitas O, Pereira N L
Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, 14040-903, Ribeirão Preto - SP, Brazil.
J Microencapsul. 2002 Sep-Oct;19(5):549-58. doi: 10.1080/02652040110105391.
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.
由于这些化合物具有生物利用度和生物可降解性，许多研究小组都对生物聚合物在缓释系统中的应用进行了研究。酪蛋白是一种天然生物聚合物，其降解会产生可被生物利用的化合物。本研究的目的是评估酪蛋白微胶囊（CAS/MC）作为以对乙酰氨基酚为模型药物的缓释系统的潜力。CAS/MC是通过在含有明胶、羟丙基纤维素（HPC）和卵磷脂的乳酸盐缓冲液中进行水相凝聚法制备的。制备后，微胶囊用或不用戊二醛作为交联剂进行处理。CAS/MC采用两种不同的方法进行载药，一种是将相对于酪蛋白50%（w/w）的药物溶解在聚合物分散液中，另一种是将药物溶解在凝聚溶液中。在酶降解试验后，通过高效液相色谱法对CAS/MC中存在的药物进行定量，并通过扫描电子显微镜和热分析（差示扫描量热法和热重分析法）对CAS/MC进行分析。药物载量约为8%（w/w），对酶攻击具有高抗性。对乙酰氨基酚熔融峰的缺失表明交联系统表面不存在药物。此外，载药伴随着系统比热容的降低，这表明稳定性降低。包封聚合物的外部形态受微囊化过程的影响。数据表明，水相凝聚和交联的微囊化过程适用于制备用于药物缓释的微囊化系统。
