Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
9 results
Search Results
Master Thesis Development and Characterization of Surface-Modified Emulsion Templated Scaffolds for Tissue Engineering Applications(01. Izmir Institute of Technology, 2024) Kocagöz, Mehmet; Dikici, Betül Aldemir; Zareıe, Esma Volga BulmuşEmülsiyon şablonlama, yüksek ve açık gözeneklilik sağlayan avantajlı bir iskele üretim yöntemidir. Bu yöntemde hidrofobik polimerlerin su ile karıştırılmasıyla yağ içerisinde su (w/o) emülsiyonları elde edilir. İç faz hacmi %74'ün üzerinde olan polimerize emülsiyonlar, yüksek iç fazlı emülsiyonlar (PolyHIPE'ler) olarak adlandırılır. Polikaprolakton, doku mühendisliğinde yaygın olarak kullanılan sentetik, biyolojik olarak bozunabilen ve biyouyumlu bir polimerdir, ancak malzemenin hidrofobik karakteri hücre-materyal etkileşimlerini sınırlamaktadır. Bu nedenle, bu çalışma kapsamında, emülsiyon şablonlama yöntemi ile üretilmiş, polikaprolakton tetrametakrilat (4PCLMA) esaslı iskelelerin biyolojik performanslarını artırmak için iskelelerin alkali muamelesi ve elde edilen iskelelerin karakterize edilmesi amaçlanmıştır. İlk olarak halka açma polimerizasyonu ile 4PCLMA pre-polimeri sentezlenmiş ve metakrilat grupları ile fonksiyon kazandırılmıştır. 4PCLMA ~%97 metakrilasyon derecesi ile başarıyla sentezlenmiş, 4PCLMA esaslı PolyHIPE'ler emülsiyon şablonlama yöntemi ile üretilmiş, üç farklı konsantrasyonda ve inkübasyon süresinde sodyum hidroksit (NaOH) ile muamele edilmiştir. NaOH işleminin iskelelerin morfolojileri, kütle kaybı, su tutma kapasitesi, mekanik özellikleri, yüzey alanı, hidrofilisitesi ve biyolojik performansı üzerindeki etkileri araştırılmıştır. NaOH uygulamasının iskelelerin ağırlığını ve mekanik mukavemetini azalttığı ancak aynı zamanda iskelelerin su tutma kapasitesini, hidrofilisitesini, yüzey alanını ve protein adsorpsiyon kapasitesini artırdığı görülmüştür. NaOH işleminden sonra PolyHIPE'lerdeki kimyasal değişiklikler spektroskopi ile doğrulanmıştır. In vitro sonuçlar, NaOH uygulamasının L929 hücreleri üzerinde sitotoksisiteye neden olmadığını ve Saos-2 hücrelerinin tutunma ve çoğalma davranışını olumlu yönde etkilediğini göstermiştir. Bu çalışma sonucunda NaOH muamelesinin, emülsiyon şablonlama ile üretilmiş doku iskelelerinin hidrofilisitesini ve biyolojik performansını artırmak adına alternatif bir yüzey modifikasyon yöntemi olarak kullanılabileceği gösterilmiştir.Master Thesis Development of a Natural Tubular Scaffold From Decellularized Parsley Stems To Be Used in Vascular Tissue Engineering Applications(01. Izmir Institute of Technology, 2024) Çevik, Merve; Dikici, Serkan; Özçivici, EnginCardiovascular diseases (CVD) are usually associated with narrowing or blockage of blood vessels and are the leading cause of death globally. By 2030, the annual incidence of CVD-related deaths is estimated to increase 23.3 million. Considering the advancements in endovascular surgery, the use of vascular grafts in cardiovascular surgery is becoming increasingly common. Autografts are the gold standard but have limitations, including limited tissue availability and complications from vessel isolation. Recently, synthetic grafts have emerged as alternatives, though they often fail due to thrombosis, atherosclerosis, intimal hyperplasia, or infection. Thrombosis, the main cause of post-implantation failure, is associated with damage or absence of the endothelial cell lining on the luminal surface of the vascular graft. To overcome the limitations mentioned so far, tissue-engineered vascular grafts (TEVG) have come into prominence. The use of decellularized plant tissues in tissue engineering applications has recently gained great importance. Accordingly, in this study, we fabricated tubular scaffolds from decellularized parsley stems and evaluated them in vitro as potential TEVGs. Our results demonstrated that native plant DNA was successfully removed, and biocompatible tubular biomaterials were successfully fabricated via chemical decellularization of parsley stems. The decellularized parsley stems showed suitable mechanical and biological properties for use as TEVG material. Finally, they were found to provide a convenient environment to form a pseudo-endothelium by recellularization with human endothelial cells prior to implantation. This study is the pioneer in the literature that reports on the potential of parsley stems to be used as a potential TEVG biomaterial.Master Thesis High-Throughput Selection of Mineralizing Peptides(01. Izmir Institute of Technology, 2024) Çulha, Gizem; Toptan, Fatih; Yücesoy, Deniz Tanıl3,4 milyar yılı aşkın protein evrimi boyunca Doğa Ana, biyomineral oluşumunu düzenleyen ve kontrol eden moleküler yollar geliştirmiştir. Biyolojik sert dokuların mükemmel hiyerarşik yapıları ve çok işlevli özellikleri uzun süredir malzeme bilimcilerine ve mühendislerine ilham kaynağı olmuştur. Proteinler tarafından sentezlenen bu doğal kompozitler, inorganik katıların çekirdeklenmesini ve büyümesini kolaylaştırır ve böylece organizmalarda mineral oluşumunu yönlendirir. Biyomineralizasyon yaşam için gerekli olmasına rağmen; düzensizliği önemli sağlık sorunlarına yol açabilir. Bu nedenle, bu mekanizmayı anlamak anormal mineral birikimiyle ilişkili hastalıklara yönelik tedavilerin geliştirilmesi açısından çok önemlidir. Nano ölçekte biyolojiden ilham alan bu tezin amacı, derin yönelimli evrim yaklaşımıyla doğal proteinlere benzer şekilde hidroksiapatit (HAp) mineralizasyonunu yönetebilen kısa katalitik peptitleri tanımlamaktır. Sonuçlarımız, benzersiz dizilere sahip peptitlerin tanımlandığını gösterdi. XRD ve FTIR analizleri yoluyla yapılan yapısal karakterizasyon, bu peptitlerin varlığında hidroksiapatit oluşumunu doğruladı. Bununla birlikte, kinetik ölçümler bu peptitlerin fizyolojik koşullar altında kalsiyum fosfat mineralizasyonunu on beş kat daha hızlı katalize ettiğini ortaya çıkardı. Bu peptitlerin, kalsiyum ve fosfat ile desteklenmiş sulu ortamda sergilediği hızlı mineralizasyon kinetiği, demineralize olmuş dokuların onarılması ve patolojik biyomineralizasyon ile ilişkili hastalıkların tedavisi için güçlü bir potansiyele işaret etmektedir. Aynı zamanda, bu peptit dizileri, diş jelleri ve diş macunu formülasyonları dahil olmak üzere klinik ürünlerin geliştirilmesinde, kemik rejenerasyonu tedavilerinde ve kontrollü mineralizasyonun önemli olduğu diğer tıbbi uygulamalarda temel unsurlar olarak hizmet edebilirMaster Thesis Cloning of Sericin-Like Proteins for Recombinant Production in Bacteria(Izmir Institute of Technology, 2019) Bostan, Fatmanur; Sürmeli Eraltuğ, Nur Başak; Bulmuş, VolgaSilk consists of two main proteins called fibroin and sericin. While fibroin is used in textile production and various biomaterial applications, sericin is considered as waste material in the textile industry. Sericin is a multi-component protein with an indefinite structure and it has been shown to be biocompatible and has biological activity. Because of the positive effects on keratinocytes and fibroblasts have led to the development of sericin-based biomaterials for the repair of skin tissue. Sericin from silkworm cocoons can be obtained by chemical treatment, enzymatic treatment and boiling in water. Although sericin can be separated from fibroin by chemical, enzymatic and boiling in water treatment methods, all these treatment methods are not enough to obtain recovery of high-quality sericin. Moreover, in these treatment methods, the exposure of sericin protein to high temperature causes even sericin protein obtained by the same method to indicate different characteristics. The fact that the obtained sericin demonstrate such major changes in the structure according to treatment methods bring inconsistencies in the quality of sericin produced as a biomaterial. The aim of the study is to produce native sequence of sericin that forms a tetramer contain each containing 38 amino acids with recombinant production in E.coli and to characterize structural properties Thus, obtaining sericin protein from the bacteria with recombinant methods will solve these problems in question The results indicate that for the first time, the conformational properties of recombinant sericin were obtained similar to the native sericin structure.Master Thesis Surface Modification of Chitosan Films/Meshes for Biomaterial Applications(Izmir Institute of Technology, 2019) Işıklı, Berçin; Tıhmınlıoğlu, FundaModification of surface of biomaterials is a great interest for many years due to first contact of surface of materials with the biological fluids. This thesis aims to investigate surface modification effect on the chemical, surface wettability, protein adsorption as well biodegradability properties of dense chitosan (Ch) and asymmetric chitosan films (ACh). The surfaces of chitosan dense and asymmetric films were modified by ion implantation technique using carbon and carbon-nitrogen hybrid ions at a fluence of 1x1015 ions/cm2 and ion energy of 20kV. Chemical compositions of the film surfaces were analyzed by Fourier transform infrared spectroscopy (FTIR-ATR). Surface hydrophobicity measurements were conducted by static contact angle measurements. Protein adsorption on unmodified and modified surfaces on films was investigated as a function of time at various pH conditions. After ion implantation on chitosan films, both C and C-Nitrogen ion implantation, the surfaces become rougher and hydrophobic having moderate wettability (����� values in the range of 72-85°) and in good agreement with FTIR-ATR data findings. It was found pH dependence of the amount of protein adsorbed on the dense chitosan films as a function of time for both un-implanted and implanted films. BSA and fibrinogen were more adsorbed on the chitosan films at pH 5. The amount of BSA and fibrinogen protein adsorption was 0.97 and 1.33 gprotein/gfilm, respectively for 60 min incubation period. Protein adsorption enhanced for C and C+N2 ion implanted samples for BSA and fibrinogen, respectively due to the hydrophobic protein surface interaction effect. In vitro degradation results showed that ACh films degrade much faster (mass loss 57 %) than Ch films (40 %) due to the porous structure at the end of 3 weeks. However, the ion implanted Ch samples degraded much slower having mass loss of 30% and 17.7% for C+N2 and C implanted samples, respectively at the end of 3 weeks compared to un-implanted Ch films as 40 %. The results are in good agreement with water sorption and surface hydrophobicity of the implanted films. This study demonstrated that surface modification, as well as structure, changes the protein sorption, wettability and biodegradation properties of the chitosan films.Master Thesis Polymer Based Extracellular Matrix Mimetics for 3d Cell Culture(Izmir Institute of Technology, 2018) Türker, Esra; Arslan Yıldız, AhuTissue engineering combines engineering principles and knowledge of life sciences to improve biological substituents. Three dimensional (3D) supporting structures, namely scaffolds obtained from biomaterials to mimic extracellular matrix (ECM) that provides suitable microenvironment for cell proliferation, migration and differentiation. In this study, poly (L-lactide-co-ε-caprolactone) (PLLCL) and collagen type I was used to fabricate scaffold by electrospinning method. In literature, collagen was often dissolved in toxic and harmful solvents that creates the major problem for cell culture applications. To overcome this problem “co-spinning” methodology is utilized for the formation of non-toxic collagen-based ECM mimetic scaffold. Collagen mixed with water-soluble carrier materials which is either polyvinylpyrrolidone (PVP) or polyvinyl alcohol (PVA) and co-electrospinning is carried out with PLLCL. Fabricated scaffolds were immersed into water to remove co-spinning agent; PVA or PVP, so only PLLCL/Collagen remained. PLLCL has homogeneous fibers in a diameter of 1.312 ± 0.22μm. The contact angle of PLLCL (136.6° ± 2.6) proved hydrophobic behavior of PLLCL material. The contact angle of the scaffold decreased up to 86.7° ± 0.1 confirming that hydrophobic behavior is decreased with the addition of collagen. Also, collagen-containing scaffolds were saturated at lower amount of protein than PLLCL, PLLCL/PVA and PLLCL/PVP scaffolds. Cytotoxicity analysis of scaffolds showed that PVA containing scaffolds had lower viability than PVP containing scaffolds; so most of the cell studies were carried out with PLLCL/ Collagen scaffolds fabricated by PVP cospinning. Cell proliferation on PLLCL/Collagen scaffolds found to be more favorable than PLLCL and PLLCL/PVP scaffolds.Master Thesis Sericin-Polymer Conjugates: Preparation and Physicochemical Characterization(Izmir Institute of Technology, 2017) Gül, Abdulkadir; Bulmuş Zareie, Esma VolgaSericin is a protein derived from silkworm, Bombyx mori, and has several useful properties as a natural biomaterial such as antioxidant character, moisturizing ability, hydrogel forming property and most importantly immunogenic inertness. The aim of this thesis is to prepare and physicochemically characterize sericin-polymer conjugates as potential natural-synthetic hybrid biomaterials with enhanced properties for drug delivery and tissue engineering applications. For this purpose, three polymers having the same degree of polymerization (n~42) and varying chemical nature, i.e. poly(oligoethylene glycol methacrylate), P(OEGMA) hydrophilic and neutral, poly(hydroxyethylmethacrylate) P(HEMA) less hydrophilic and neutral, and poly(dimethylaminoethyl methacrylate) P(DMAEMA) hydrophilic and cationic after quaternization, were first synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. Each polymer was characterized via nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). Separately, molecular weight and isoelectric point of sericin were characterized using various techniques including Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) and High-Resolution Two-Dimensional Polyacrylamide Gel Electrophoresis (2D-PAGE). Polymers were then covalently conjugated to sericin using NHS/EDC chemistry. The conjugates were characterized using SDS-PAGE, GPC and DLS (Dynamic Light Scattering). The SDS-PAGE and GPC results showed the successful preparation of the conjugates. DLS revealed that the hydrodynamic size of P(OEGMA) and P(DMAEMA) polymers and their conjugates were between 1 and 10 nm as they are soluble in PBS and do not form aggregates. Unlike the other two polymers, although the size of P(HEMA) polymer was observed to be 3.24 ± 0.62 nm, the DLS measurements of P(HEMA) conjugates indicated the presence of self-organization and aggregation of Sericin-P(HEMA) conjugates in aqeuous solution. Consequently, the size of sericin-P(HEMA) conjugates were found to be 530 ± 60.83 and 223.3 ± 25.2, respectively.Master Thesis Hydrogels and Self-Assemled Nanostructures Based on Wool Keratose(Izmir Institute of Technology, 2017) Pakkaner, Efecan; Top, AybenIn this study, water soluble keratose proteins were extracted from “Ovis aries” wool using peracetic acid oxidation with a yield of 35 ± 5 %. Wool samples and the extracted keratose proteins were characterized by using FT-IR, XRD, SEM and TGA techniques. α-keratose fractions (MW = 43-53 kDa) along with cleaved fragments of α-keratoses with molecular weights between 23 and 33 kDa were identified in the extracted protein mixture using SDS-PAGE analysis. DLS and AFM experiments indicated self-assembled globular nanoparticles with diameters of 20-40 nm formed at 5 and 10 mg/ml keratose concentrations. On the other hand, at 10 % w/v keratose concentration interconnected keratose hydrogels with pore sizes of 6 ± 4 and 7 ± 4 μm were obtained upon incubation at 37 and 50 °C, respectively. Storage moduli (G’) of these physical hydrogels were increased from ~100 to ~1000 Pa, as gelation temperature was increased from 37 to 50 °C. Hydrogels were also obtained at 7.5 % w/v keratose concentration by the addition of a crosslinker, THPC. Amine group:crosslinker ratio was used as 1:1, 1:2 and 1:4. As the amount of crosslinker increased, network transformed from fibrous to more planar structures exhibiting a significant decrease in average pore size from 24 to 11 μm. G’ values of the crosslinked hydrogels were obtained between ~1 and ~5 kPa tuned by the crosslinking amount. Cell interaction properties of a select physical hydrogel prepared at 37 °C was tested using CCK-8 assay. It was observed that the keratose hydrogel supported L929 mouse fibroblast cell proliferation as much as collagen, which suggests that these keratose hydrogels can be promising candidates in soft tissue engineering applications.Master Thesis Investigation of Biocompatibility of Calcium Phosphate Based Materials and Cements(Izmir Institute of Technology, 2014) Karataş, Özlem; Çiftçioğlu, Muhsin; Harsa, Hayriye ŞebnemCalcium phosphate cements (CPCs) have been extensively investigated due to their excellent biocompatibility, osteoconductivity, potential resorbability in dentistry and orthopedics. They have numerous advantages over other calcium phosphate-based materials. The CPC precursor powders were prepared in the initial stage of this work. Tetracalcium phosphate (TTCP) powders coded as TTCP-1 (obtained from H3PO4 and CaCO3) and TTCP-2 (obtained from NH4H2PO4 and CaCO3) were prepared by heat treatment of the calcium and phosphate source mixtures at 1350°C. Brushite powders were produced by aqueous chemical methods. A series of CPCs (HA cements) were prepared by using the TTCP-1 and brushite powders which were mixed with 0.2 M and 0.3 M phosphate buffer solutions at three different solid/liquid ratios (2.4, 2.7 and 3.2 g/ml) with three different HA initial seed contents (3%, 1.5% and 0.0 wt% ). The setting times of CPCs were determined to be in the 3.5-24 minute range. The phase structure and surface morphology of the cements and precursor powders were characterized by XRD and SEM. XRD analysis of powders revealed the presence of the characteristic TTCP and brushite peaks. XRD analysis also indicated that all cement samples were composed by HA phase with different crystallinity and other phases were not detected. Rod and plate-like hydroxyapatite crystals were observed in the SEM micrographs of all CPCs. Cytotoxicity testing was performed using the MTT (3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyl tetrazolium bromide) assay to determine the number of viable cells in the presence of powders and HA cements. Cytotoxicity results indicated that brushite powder caused sharp decreases in cell viability at the end of 24, 48 and 72 hours at all powder extract concentrations. TTCP-1 and TTCP-2 powders unlike brushite had no toxic effect with cell viability values over 74 %. Almost all CPCs prepared in this work had no cytotoxic effects.