Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Asymmetric Membrane Tablet Coatings for Controlled-Release of Drugs(Izmir Institute of Technology, 2002) Yenal, Hacer; Alsoy Altınkaya, SacideMost of the controlled release systems developed for drug delivery applications dependon membrane technology. The dense structure of the membrane in conventional controlled release systems prolongs the release of drug. To eliminate this disadvantage while maintaining the benefits of dense membrane systems, an asymmetric type of coating was applied on tablets. Coatings were prepared from cellulose acetate, acetone, water solution by phase inversion technique. To determine the release rate of drug, dissolution studies on tablets were performed according to United States of Pharmacopeia (USP). In these studies, the effects of composition of the polymer/solvent/nonsolvent, coating time, number of coating layers, evaporation conditions and the nonsolvent type on the release rate of the drug and the structure of membrane were investigated. Experiments were designed using commercial software package Design-Expert and a quadratic model equation was obtained to predict the effect of composition of cellulose acetate, acetone and water on the release rate of drug. The advantage of asymmetric type coating over the conventional dense type coating was further demonstrated by measuring the permeabilities of both type of coatings. In addition, the structures of membranes were analyzed using scanning electron microscope (SEM) micrographs.Master Thesis Development of Ph-Controlled Triggering Mechanisms for Controlled Release of Lysozyme(Izmir Institute of Technology, 2011) Boyacı, Derya; Yemenicioğlu, AhmetIn this study, zein and whey protein (WP) based films and their blends and composites have been prepared to obtain pH-controlled triggering mechanisms for controlled release of lysozyme. The total amount of lysozyme released from standard zein films was not considerably affected from changes in pH between 7.3 and 5.3 since this hydrophobic biopolymer lacked charged ionisable groups to bind lysozyme ionically. In contrast, incorporation of lentil protein isolate (LPI) into zein created a composite structure and caused binding of positively charged lysozyme (pI>9.0) on negatively charged groups of LPI (pI: 4.5-6) within the film matrix in release medium with pH between 5.3 and 7.3. The amount of bound lysozyme in zein-LPI composites increased linearly as LPI concentration increased between 1,5 and 4,5 mg/cm2 at pH 7.3. The release of bound enzyme could be triggered by reducing pH of release medium from 7.3 to 4.3, down below pI of LPI. On the other hand, films of WP (pI≈5.2) bind considerable amount of lysozyme due to their inherent net negative charges close to neutrality. The release of bind lysozyme could be trigged as pH of release medium reduced from 6.0 to 3.0, down below the pI of WP. The preparation of WP-oleic acid blend and WP-bees wax composites increased the film porosity and amounts of released lysozyme from films at pH 4.5 and 5.0, by 2-4 and 1.2-1.5 folds, respectively. The zein and WP based films containing 0.7 to 1.4 mg/cm2 lysozyme showed good antimicrobial activity against Listeria innocua. This work showed the potential of creating pH-controlled release systems during antimicrobial packaging of food.