Layered and composite biopolymers: Mechanical, physical and antimicrobial properties

In this thesis, two oppositely charged biopolyelectrolytes –alginate and chitosan- were focused on. The interactions between these biopolymers and the effect of surfactants on these biopolymers were studied. Thesis is composed of three chapters. In first chapter. The changes in mechanical properties of the calcium and barium crosslinked alginate hydrogel beads, when sodium dodecyl sulfate (SDS) and Brij 35 were incorporated into the gel structure, were studied. SDS and Brij 35 are negatively charged and nonionic surfactants, respectively. Alginate concentration, types and concentrations of crosslinker and surfactant were found as parameters which affect the elastic properties of alginate hydrogel beads. Modulus of elasticity of the alginate gels increased when SDS was added and decreased in the presence of Brij 35. Therefore it is considered that SDS increases the negative charge density on alginate chain by binding to the chain via hydrophobic interactions. On the other hand, Brij 35 decreased the charge density. Second chapter focuses on the preparation of the alginate – chitosan polyelectroylte multilayer (PEM) films and the effect of surfactants on them by characterizing the samples using ellipsometry, X-ray reflectometry and atomic force microscopy. Results showed that SDS increased the thickness of the PEM films by increasing the adsorbed amount of mass of the alginate – chitosan system. In third chapter, it was aimed to develop a potent wound dressing agent by preparing cerium(III) crosslinked alginate-chitosan films. Mechanical and antimicrobial characterization of the samples indicated the potential of cerium(III) crosslinked alginate-chitosan as wound dressings. This graduate thesis project was derived from the results of the experiments and measurements, which were conducted within the scope of joint doctoral agreement between İstanbul Teknik Üniversitesi and Technische Universität Berlin. Graduate student was supported by Scientific and Technical Research Council of Turkey (TÜBİTAK) BİDEB 2214/B joint doctoral scholarship program.