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, HasanRecently 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 Use of Silica-Based Sorbents for Separation and Preconcentration of V (iv) and V (v)(Izmir Institute of Technology, 2010) Erdem, Aslı; Eroğlu, Ahmet EminVanadium is one of the essential trace elements for plants and animals. While it is beneficial for normal cell growth, it becomes toxic at high concentrations. In the present study, silica-based sorbents were prepared and used for sorption/speciation of vanadium from waters prior to inductively coupled plasma mass spectrometric (ICP-MS) determination. Among the sorbents developed, 3-APTES-modified silica, has been shown to be an efficient material for the speciation of vanadium. Solution pH of 2.0 and 3.0 can be used for the respective sorption of V(V) and the total vanadium, namely, V(IV) and V(V). The concentration of V(IV) can then be calculated from the difference. Desorption from the sorbent was realized with 0.5 M thiourea prepared in 0.2 M HCl. The validity of the method was checked via spike recovery experiments with four different types of water; namely, ultra pure, bottled drinking, tap, and sea water. The method works efficiently (>85% recovery) for ultra pure, bottled drinking, and tap water; and a relatively high recovery (>70%) was obtained even for sea water which has a very heavy matrix. For trypsin-immobilized silica, the sorption percentage towards V(IV) and V(V) is almost constant (>90%) within the pH range 4.0-8.0 which demonstrates the possibility of using this sorbent for the sorption of both vanadium species. The sorption of vanadate ion was investigated both from a kinetic perspective and also in terms of Freundlich, Dubinin-Radushkevich and Langmuir isotherm models; and Langmuir model was found to describe the sorption better for both of the functionalized silicas.