M.S. Theses
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Browsing M.S. Theses by Subject "Amino acid sequence."
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Item Amino acid conjugated alginate - graphene oxide scaffolds(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2017., 2017.) Şahin, Ecem.; Garipcan, Bora.; Ak, Ayşe.In this thesis, fabrication and characterization of neat alginate and alginate/graphene oxide (GO) composite 3D porous scaffolds were investigated in order to achieve a material suitable for wound care applications with enhanced properties such as biocompatibility, high mechanical strength, stability, high absorbance and positive cell behaviour. Alginate (Al) was used as the main polymer and GO was used as additive. L-Cysteine (Cys) was conjugated on GO in order to enhance biocompatibility. Initially, neat Al scaffolds were fabricated by ionic crosslinking (CaCl2 as cross-linker) and lyophilisation. Then GO (1mg/ml) was added to the structure and Al/GO scaffolds with different crosslinker concentrations (0.01-0.03 M) were fabricated in order to determine optimal crosslinker concentration. Next, 0.03M crosslinker concentration was kept constant and scaffolds with different GO concentrations (0.5-2 mg/ml) were prepared in order to determine optimal GO concentration. Finally, Cys was immobilized to GO (1:1 ratio) and Al-3/CysGO-0.5 scaffold was fabricated. FTIR and SEM were used for the characterization of Al/GO scaffolds. Swelling ratio and porosity were investigated by conducting swelling test. Viscoelasticity of the non-lyophilized hydrogels was investigated with rheometry method. Viability of fibroblast cells was investigated by MTT assay. According to the results, adding GO to the structure provided stability and immobilization of Cys increased biocompatibility, and a porous, more stable material with high absorbance, biocompatibility and positive cell response was obtained.|Keywords : Alginate, 3D scaffold, graphene oxide, wound healing, composite.Item Self - assembly technique for producing l-arginine / hydroxyapatite coatings on Ti6Al4V implants(Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2017., 2017.) Duru, Ilayda.; Ege, Duygu.Inthepresentstudy, weintroduceaself-assemblymethodtoproduceL-arginine (L-Arg)/Hydroxyapatite (HA) coatings. Firstly, Ti6Al4V substrates were etched in a concentrated solution of HCl/H2SO4. ZrO2 was reactively sputtered on Ti6Al4V as an intermediate layer between HA and Ti6Al4V. Reactive magnetron sputtering was performed at 200 W and 200 ◦C for 4 hours. HA was deposited on ZrO2 layer by electrophoretic deposition (EPD) at 30 V in 205 seconds. HA suspension was obtained byultrasonicandmagneticagitationof1gHAin35mlisopropanolfor3hours. Finally, thesampleswereimmersedinL-Argsolutioninphosphatebufferedsaline(pH=7.4)and incubated at room temperature for 24 hours. Scanning Electron Microscopy (SEM), XRay Diffractometry (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman and X-Ray Photoelectron Spectroscopy (XPS) analyses were performed to characterize the coated and uncoated Ti6Al4V implants. Raman and XRD spectra of ZrO2 layer demonstrated the characteristic peaks of monoclinic structure. The most characteristic bands on Raman spectrum were a doublet at 181 and 189 cm−1, a broad peak at 477 cm−1. Moreover, XRD spectrum revealed that ZrO2 coating had a monoclinic crystal structure. FTIR and C1s spectra spectra of L-Arg/HA coating revealed the formation of new bonds which were C-O/N and protonated O-C=O. According to XPS analyses, C/Ca ratio increased with the addition of L-Arg and Ca/P ratio was decreased. It can be concluded that L-Arg particles were self-assembled on HA layer by binding of the carboxyl group of L-Arg to calcium atoms of HA. Overall, L-Arg/HA coatings were successfully coated on ZrO2-coated Ti6Al4V orthopedic implants by self-assembly method.|Keywords : Self-assembly, amino acid, orthopedic implant.