Browsing by Subject "encapsulation"
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Item Open Access In situ synthesis of biomolecule encapsulated gold-cross-linked poly(ethylene glycol) nanocomposite as biosensing platform: A model study(Elsevier BV, 2010) Odaci, D.; Kahveci, M.U.; Sahkulubey, E.L.; Ozdemir, C.; Uyar, Tamer; Timur, S.; Yagci Y.In situ synthesis of poly(ethylene glycol) (PEG) hydrogels containing gold nanoparticles(AuNPs) and glucose oxidase (GOx) enzyme by photo-induced electron transfer process was reported here and applied in electrochemical glucose biosensing as the model system. Newly designed bionanocomposite matrix by simple one-step fabrication offered a good contact between the active site of the enzyme and AuNPs inside the network that caused the promotion in the electron transfer properties that was evidenced by cyclic voltammetryas well as higher amperometric biosensing responses in comparing with response signals obtained from the matrix without AuNPs. As well as some parameters important in the optimization studies such as optimum pH, enzyme loading and AuNP amount, the analytical characteristics of the biosensor (AuNP/GOx) were examined by the monitoring of chronoamperometric response due to the oxygen consumption through the enzymatic reaction at − 0.7 V under optimized conditions at sodium acetate buffer (50 mM, pH 4.0) and the linear graph was obtained in the range of 0.1–1.0 mM glucose. The detection limit (LOD) of the biosensor was calculated as 0.06 mM by using the signal to noise ratio of 3. Moreover, the presence of AuNPs was visualized by TEM. Finally, the biosensor was applied for glucose analysis for some beverages and obtained data were compared with HPLC as the reference method to test the possible matrix effect due to the nature of the samples.Item Open Access An Object memory for an object-oriented database management system(Bilkent University, 1988) Kesim, F. NihanObject-oriented paradigm is an approach that can be applied in various areas of computing. In this approach, each entity is represented by an object which captures the state and the behaviour of the entity. In this thesis, a focused survey of object-oriented paradigm in general and object-oriented database management systems in particular has been carried out and an object memory module is designed and implemented for an object-oriented database management system prototype. The object memory module handles the representation, access and manipulation of objects in the system and provides the primitive functions that are necessary in the development of the prototype.Item Open Access Self-assembly of peptide nanofibers and their mechanical properties(Bilkent University, 2012) Erkal, Turan SelmanPeptide nanofibers have been drawing attention because of their versatile, tailorable and functional properties in various research areas. The self-assembly mechanism of peptides and peptide amphiphile molecules is generally based on noncovalent interactions like hydrophobic, electrostatic and metal-ligand interactions. In this thesis, I investigated hydrophobic interaction of peptide amphiphiles (PAs) with other hydrophobic molecules and effect of pH change on self-assembly mechanism. The zinc phthalocyanine molecule was used as a hydrophobic probe to be encapsulated by peptide amphiphile molecules, which help to dissolve the molecule in water instead of an organic solvent. Charge neutralization of PAs by pH change led to nanofiber formation, which resulted in encapsulation and organization of zinc phthalocyanine molecules. The degree of self-assembly by pH change determined non-linear optical properties of zinc phthalocyanine molecule. Besides, morphological, mechanical and spectroscopic properties of phthalocyanine containing peptide nanofibers were characterized by TEM, SEM, oscillatory rheology, UV-Vis, fluorescence and circular dichroism spectroscopy. The mechanical properties of peptide and PA hydrogels and nanofibers have an essential place to determine applicability in different areas. Especially, PA and peptide molecules have been widely used in regenerative medicine studies and the stiffness of the extracellular matrix has a significant role on cellular behavior. In this thesis, viscoelastic properties of the peptide and PA gels were studied by oscillatory rheology. In addition to characterization of bulk mechanical properties of peptide gels, adhesion and stiffness of peptide nanofibers were determined by Atomic Force Microscopy.