M.S. Theses

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Browsing M.S. Theses by Subject "Amino acids."

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    Amino acid conjugated self assembly molecules modified SI wafers
    (Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2014., 2014.) Aktaş, Bengü.; Garipcan, Bora.
    In this thesis, Si wafer surface was modi ed with newly synthesized selfassembled monolayers to mimic a biocompatible micro-environment for the cells and to observe their behavior. Begin with; Si wafer is chosen as its availability is easy and well-established structures can be obtained in the surface modi cation without any interference. In the rst step, Si wafers were cleaned and modi cation of surfaces was carried out with amino acid conjugated self-assembled molecules [Histidine-Self Assembled Molecule (His-SAM), and Leucine-Self Assembled Molecule (Leu-SAM)], (3-aminopropyl)triethoxysilane (APTES) and also poly-L-ornithine (PLO). The characterization of these samples were analyzed with contact angle measurements, X-Ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), and ellipsometry. After characterization results were acquired, the cell culture studies were performed with L929 cells. In order to obtain information about cell proliferation, MTT assay (a colorimetric assay) was performed. According to these results, enhanced cell proliferation was achieved by the contribution of surface functional groups. Consequently, it has been observed that these controlled molecular structures on the surfaces of materials have a great potential for biomedical applications.|Keywords : Silicon Wafer, Surface Modi cation, Self-assembled Molecules (SAMs), Amino Acids.
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    Amino acid conjugated self-assembled molecules modified titanium surfaces
    (Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2019., 2019.) Türkaydın, Müge.; Garipcan, Bora.
    The goal of this thesis is to increase biocompatibility of titanium (Ti) surfaces, which is an extensively used biomaterial in medicine, by an easy and timesaving surface modification procedure. For this purpose, 3-aminopropyltriethoxysilane (APTES) molecule was conjugated by 3 different amino acids (histidine, leucine, and tryptophan). Newly synthesized molecules were used to form amino acid conjugated self-assembled monolayers on titanium surface. After modification of the surfaces by each of the amido amino acids, histidine and leucine amino acids were chosen to make up hydrophilic and hydrophobic regions on the surface and they were mixed with changing concentrations (v/v, 80:20, 50:50, 20:80). X-ray photoelectron spectroscopy (XPS) analysis and water contact angle measurements were performed for the characterization studies of all of the modified surfaces. Human osteoblast cells culture studies were performed on the surfaces, which were modified by this method aimed at improving the biocompatibility of titanium, in order to investigate cell viability on the modified surfaces.|Keywords : Titanium, Surface Modification, Self-assembled Molecules (SAMs), Amino Acids, Biocompatibility.
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    Protein adsorption on amino acid conjugated self assembled molecules
    (Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2015., 2015.) Eren, Sezin.; Garipcan, Bora.
    In this thesis, novel amino acid (conjugated histidine, leucine, serine, tryptophan) conjugated self-assembled molecules (SAMs) were synthesized and used to modify model metallic [Gold, (Au)] and inorganic [Silicon Oxide, (SiO2)] surfaces to investigate protein adsorption. In the first step, Au and SiO2 surfaces were cleaned and modification of surfaces were carried out with 3-mercaptopropanoyl and 3 - (trimethoxysilyl) propane functional groups conjugated amino acids (for Au; histidine, leucine, serine, tryptophan, for SiO2; histidine and leucine), respectively. Syntheses of amino acid conjugated SAMs were characterized with 1H-Nuclear Magnetic Resonance (1H-NMR) Spectroscopy. Au and SiO2 surfaces modified with amino acid conjugated SAMs were characterized water contact angle measurements. We aimed to manipulate and change the adsorption of the proteins (Albumin, Fibrinogen and Immunoglobulin G) on these surfaces using amino acid conjugated SAMs. Protein adsorption was investigated insitu by using Quartz Crystal Microbalance (QCM) biosensors. According to results, target proteins have shown different affinity to the amino acid conjugated Au and SiO2 coated crystals depending the type of the amino acids and concentration. For instance, according to comparison of Histidine modified SiO2 and Au surfaces, properties of surfaces have shown a clear difference and effect on protein adsorption. In addition, according to comparison of Leucine modified SiO2 and Au surfaces, properties of surfaces have shown a clear effect on protein adsorption as having the same surface chemistry. Consequently, it has been observed that these controlled chemistry on the surfaces of materials have a great potential to manipulate protein adsorption for biomedical applications.|Keywords : Self-Assembled Monolayers, Amino acids, Surface Modification, Protein Adsorption, Quartz Crystal Microbalance (QCM) Biosensors.