Phd Degree / Doktora

Permanent URI for this collectionhttps://hdl.handle.net/11147/2869

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  • Doctoral Thesis
    Natural and Synthetic Silica Incorporated Chitosan Composite Scaffolds for Bone Tissue Engineering Applications
    (İzmir Institute of Technology, 2016) Tamburacı, Sedef; Tıhmınlıoğlu, Funda; Tıhmınlıoğlu, Funda; Havıtçıoğlu, Hasan
    Recently bone tissue engineering studies have focused on the development of 3D scaffolds that can organize the tissue regeneration in natural way with appropriate porosity and reinforced the structure. Natural polymer-based composites have been focused with more attention than synthetic polymer composites for bone tissue engineering applications because of their biocompatibility and biodegradability. In this work, the goal was to combine the useful biomaterial properties of both chitosan and silica to design biocomposite organic/inorganic biomaterials for bone tissue engineering applications. The composite scaffolds were fabricated by freeze drying method bu using two different silicas; natural silica; Diatomite and synthetic silica, octa (tetramethylammonium) polyhedral oligomeric silsesquioxanes (OctaTMA-POSS). The effects of silica type and loading on the mechanical, morphological, chemical, surface properties, wettability and biocompatibility of composite scaffolds were investigated and characterized by using SEM, AFM, contact angle analysis, swelling study, protein adsorption assay, biodegradation and biomineralization tests. WST-1 cytotoxicity, cell proliferation with rezasurin and alkaline phosphatase activity assays were performed to determine biological activity of the composite scaffolds. In vitro biomineralization on scaffolds was determined by Von Kossa and Alizarin red staining. POSS and diatomite incorporation increased the surface roughness. Chitosansilica composites exhibited 82-90% porosity. Wet chitosan-silica composite scaffolds exhibited higher compression moduli compared to pure chitosan scaffold in 67.3- 81.4kPa and 78.1 to 107.6kPa range respectively. Average pore size range of chitosandiatomite and chitosan-POSS composite scaffolds was obtained as 15-180μm and 220- 300μm, respectively. Results indicated that chitosan-silica composites did not show any cytotoxic effect on 3T3, MG-63 and Saos-2 cell lines. Chitosan-silica composites were found to be favorable for osteoblast proliferation. Diatomite and POSS incorporation showed promising effects with enhancing ALP activity on hFob cells. Therefore, these composite scaffolds could be used for bone tissue engineering applications.
  • Doctoral Thesis
    Investigation of Hemostatic Biomaterials Containing Plant Extracts
    (Izmir Institute of Technology, 2014) Uslu, Mehmet Emin; Bayraktar, Oğuz; Başal Bayraktar, Güldemet; Akhisaroğlu, Mustafa
    Haemostasis in other words a process which causes bleeding to stop is very important in injury. Recent researches were focused on discovery of haemostatic agents and developing biomaterials which transfer them to the injury side. Therefore plant extracts and three dimensional biomaterials were widely investigated. In this research the extract of Equisetum arvense was investigated as a coagulatory agent. Silk fibroin-hyaluronic acid mixture was used for the preparation of three dimensional sponge like biomaterials. The prepared sponge forms could also be used as scaffold for wound healing. In this research effect of extraction parameters on extract composition and bioactivity was investigated. Effect of extraction parameters were analyzed on 6 factors at 3 levels. It was seen that extraction parameters had high influence on both composition and bioactivity of the prepared extract. Although it was reported that the extract of equisetum arvense had anticoagulant activity, in this research it was shown that changing parameters caused variation of extract bioactivity from anticoagulant to coagulant as a result of changing extract composition. Addition of extract into silk fibroin-hyaluronic acid mixture caused proteins to precipitate as a result of interaction between protein and phenolic compounds. As a result of this precipitation significant decrease in the mechanical strength of biomaterial was observed. In order to minimize this interaction, plant extract was added into the silk fibroin after mixing with hyaluronic acid solution. As a result, mechanical strength and pore size of the biomaterial were increased and pore distribution became more regular. Also biomaterial gained tubular network on both vertical and horizontal dimensions. This would help the proliferation and migration of the fibroblast cells and moreover prevent the formation of scar tissue.
  • Doctoral Thesis
    Preparation and Characterization of Polymeric Scaffolds for Nerve Tissue Engineering Applications
    (Izmir Institute of Technology, 2014) Büyüköz, Melda; Alsoy Altınkaya, Sacide; Erdal, Şerife Esra
    The major goal in tissue engineering is to develop three-dimensional biomimetic scaffolds which can provide an optimal environment for cell adhesion, proliferation, differentiation and guide new tissue formation. In this study macroporous, nanofibrous gelatin scaffolds in the form of a disc and channeled conduit were prepared for nerve tissue engineering applications. Alginate microspheres have been integrated into the scaffolds to deliver nerve growth factor (NGF) to differentiate PC12 cells. Methods combining thermally induced phase separation technique with porogen leaching and injection molding were used to manifacture disc shaped and channeled nanofibrous scaffolds, respectively. Microcarriers loaded with NGF were fabricated by water-in-oil emulsification technique and attached in the scaffold by chemical crosslinking with carbodiimide reaction. The relationship among processing parameter, porosity, pore size, interpore connectivity and the mechanical properties were investigated. In addition release kinetics of NGF from the particles were determined and viability, proliferation and differentiation of PC12 cells in the scaffolds were evaluated. The fiber sizes of nanofibrous scaffolds were found similar to the size of natural collagen fiber bundles. In nanofibrous scaffolds, the dimensional stability and in vitro degredation rates improved when compared to solid walled scaffolds. The release rate of NGF from the particles was controlled by the alginate concentration and poly(L-lysine) coating. Integrating NGF into the nanofibrous gelatin scaffold in encapsulated form reduced amount of NGF and time required for the differentiation of PC12 compared to free NGF directly added to the cells.