Person: DEMİR, SERAP
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DEMİR
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SERAP
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Publication Metadata only Preparation and characterization of UV-curable polymeric support for covalent immobilization of xylanase enzyme(ELSEVIER, 2011) KAHRAMAN, MEMET VEZİR; Akdemir, Zumrut Seden; Demir, Serap; Kahraman, M. Vezir; Apohan, Nilhan KayamanThe hydroxyl group of poly(ethylene glycol) monoacrylate (PEGMA) was activated by 1 1'-carbonyldiimidazole (CDI) and then a xylanase enzyme was immobilized to amine active PEGMA UV-curable polymeric support formulation was prepared by mixing the xylanase bonded PEGMA aliphatic polyester 2-hydroxyethyl methacrylate (HEMA) poly(ethylene glycol) diacrylate (PEGDA) and photoinitiator After UV irradiation the enzymatic activity of the polymeric matrix was evaluated and compared with the corresponding free enzyme By immobilization the temperature resistance of the enzyme was improved and showed maximum activity at 60 C pH dependent activities of the free and immobilized enzymes were also investigated and it was found that the pH of maximum activity for the free enzyme was 60 while for the optimal pH of the immobilized enzyme was 65 The immobilized enzyme retained 75% of its activity after 33 runs The morphology of the polymeric support was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) coupled with SEM was used to explore the chemical composition The results have confirmed the evidence of enzyme in the structure of the polymeric material (c) 2010 Elsevier B V All rights reservedPublication Metadata only Immobilization of alpha-amylase onto poly(glycidyl methacrylate) grafted electrospun fibers by ATRP(ELSEVIER, 2015) OKTAY, BURCU; Oktay, Burcu; Demir, Serap; Kayaman-Apohan, NilhanIn this study, novel alpha-amylase immobilized poly(vinyl alcohol) (PVA) nanofibers were prepared. The PVA nanofiber surfaces were functionalized with 2-bromoisobutyryl bromide (BiBBr) and followed by surface initiated atom transfer radical polymerization (SI-ATRP) of glycidyl methacrylate (GMA). The morphology of the poly(glycidyl methacrylate) (PGMA) grafted PVA nanofibers was characterized by scanning electron microscopy (SEM). Also PGMA brushes were confirmed by X-ray photo electron microscopy (XPS). alpha-Amylase was immobilized in a one step process onto the PGMA grafted PVA nanofiber. The characteristic properties of the immobilized and free enzymes were examined. The thermal stability of the enzyme was improved and showed maximum activity at 37 degrees C by immobilization, pH values of the maximum activity of the free and immobilized enzymes were also found at 6.0 and 6.5, respectively. Free enzyme lost its activity completely within 15 days. The immobilized enzyme lost only 23.8% of its activity within 30 days. (C) 2015 Elsevier B.V. All rights reserved.Publication Metadata only Immobilization of pectinase on polyethyleneimine based support via spontaneous amino-yne click reaction(ELSEVIER, 2020) OKTAY, BURCU; Oktay, Burcu; Demir, Serap; Kayaman-Apohan, NilhanThe immobilization of an enzyme can improve catalytic activity, stability, and reusability of its. In this study, we investigated a new method for enzyme immobilization. Alkyne-pectinase was first immobilized on the polyethyleneimine-based cryogel via a spontaneous amino-yne click reaction under very mild conditions and then the apple juice was clarified. Amino-yne click reactions do not need any photoinitiator or catalyst, unlike other click reactions. The immobilization efficiency of the alkyne pectinase was 90%. The immobilized enzyme continued to retain 70% of its initial activity after 60 days. An improvement observed in the pH tolerance in the range of 6.5-8.0. The higher thermal tolerance of the immobilized pectinase was increased above 50 degrees C. Immobilized pectinase showed 100% activity at 55 degrees C and pH 6.5. The clarification rate of apple juice was achieved about 50% by the pectinase immobilized support. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.Publication Metadata only Magnetic nanoparticle containing thiol-ene crosslinked hydrogels for controlled and targeted release of hydrophobic drugs(WILEY, 2018) OKTAY, BURCU; Oktay, Burcu; Demir, Serap; Kayaman-Apohan, NilhanThis study reports a straightforward but very effective method to produce nanocomposite hydrogels for targeted drug delivery system. An organic network containing both hydrophilic and hydrophobic components was obtained using thiol-ene cross-linking. Magnetite nanoparticles (MNPs) were synthesized by chemical co-precipitation. The surface of the MNPs was modified with allyl groups to avoid agglomeration. Composite hydrogels were prepared by addition of surface modified MNPs to hydrogel formulation at different ratios. The prepared composite hydrogels were investigated for their ability to loading and release hydrophobic drugs tamoxifen and clarithromycin. The morphological and structural characterizations of MNPs were performed by Fourier transform infrared spectroscopy (FT-IR) and Environmental scanning electron microscopy (SEM) and Environmental scanning transmission electron microscopy (STEM). Moreover the superparamagnetic behavior of the hydrogels was studied by a vibrating sample magnetometer (VSM). The saturation magnetization values increased with the magnetite content. Swelling, gel content and degradation of the hydrogels were examined. According to the loading of drugs, the maximum loading efficiency was 91% for tamoxifen and 70% for clarithromycin due to the stronger hydrophobic interactions. In vitro release studies showed that controlled release of the drugs occurred over a prolonged period of time. Therefore, drug loaded hydrogels can be considered as potential long-term sustained drug release systems. POLYM. COMPOS., 39:E200-E209, 2018. (c) 2016 Society of Plastics EngineersPublication Metadata only Preparation of a Poly(ethylene glycol)-Based Cross-Linked Network from a Click Reaction for Enzyme Immobilization(WILEY-V C H VERLAG GMBH, 2019) OKTAY, BURCU; Oktay, Burcu; Demir, Serap; Kayaman-Apohan, NilhanIn this study, a polyethylene glycol (PEG)-maleimide film was prepared by a thiol-ene click reaction. The covalent immobilization of amylase was carried out onto the PEG-maleimide based photo-curable network via epoxy and C=O groups without any linker. The epoxy and carbonyl groups on the PEG backbone improved the affinity of the enzyme. The immobilization yield of amylase onto the film was 72.46%. The immobilization capacity was also determined as 313 mg/g. The thermal stability of amylase improved via covalent attachment. Immobilized amylase showed maximum activity at 40 degrees C and pH 6.5. The immobilized amylase continued to retain 66% of its initial activity after 30 days.Publication Open Access Poly(lactic acid) nanofibers containing phosphorylcholine grafts for transdermal drug delivery systems(2022-06-01) OKTAY, BURCU; DEMİR, SERAP; KAYAMAN APOHAN, NİLHAN; OKTAY B., Eroglu G. O., DEMİR S., KURUCA D. S., KAYAMAN APOHAN N.The continuous and prolonged releases of chemotherapeutic drugs are required for successful treatment in cancer treatment. The project focused on a new material design to meet this requirement. We developed a constant and sustained release system and investigated the release profiles of Paclitaxel (PTX). Polylactic acid (PLA) nanofiber surface was grafted with poly (methacryloyloxyethyl phosphorylcholine) (PMPC) by the UV-induced grafting method. The morphological structure of the PLA nanofibers did not change with an increase in the MPC content. PMPC blocks contribute to the solubility of PTX, which shows low resolution. When the amount of MPC is 5%, the PTX loading efficiency increased two times compared with PLA nanofiber. The nanofiber mats exhibited an initial fast release during the first 3 h. Endothelial cells were cultured on nanofiber mats to investigate whether this material was toxic or not. The mats showed good biocompatibility with HUVEC. Thus, it was confirmed that nanofiber mats would not be toxic when releasing drugs during in vivo use. We think that PMPC facilitates the pass of drugs through the lipid-rich biological membrane and so anticancer drugs can be delivered to direct tumor sites. (C) 2022 Elsevier Ltd. All rights reserved.Publication Metadata only Preparation, characterization, and drug release properties of poly(2-hydroxyethyl methacrylate) hydrogels having beta-cyclodextrin functionality(JOHN WILEY & SONS INC, 2008) OGAN, AYŞE; Demir, Serap; Kahraman, M. Vezir; Bora, Nil; Apohan, Nilhan Kayaman; Ogan, AyseA new beta-cyclodextrin urethane-methacrylate monomer was synthesized from the reaction of toluene-2,4-diisocyanate, 2-hydroxyethyl methacrylate (HEMA), and beta-cyclodextrin (beta-CD). Based on inclusion character of beta-CD, a series of hydrogels were prepared by irradiating the mixtures of beta-cyclodextrin urethane-methacrylate monomer (beta-CD-UM), poly(ethylene glycol) diacrylate (PEG-DA), HEMA, and the photoinitator. Gel percentages and equilibrium swelling ratios (%) of hydrogels were investigated. It was observed that the equilibrium-swelling ratio increased with increasing beta-CD-UM content in the hydrogel composition. SEM images demonstrated that beta-CD-UM based hydrogel have porous fractured surface. In this study four different drug molecules, salicylic acid, sulfathiazole, rifampicin, and methyl orange as model drug, which are capable of forming inclusion complexes with beta-CD were chosen. For sulfathiazole and rifampicin, the drug loadings are very low (0.04 and 0.008 mmol/g dry gel), whereas methyl orange and salicylic acid drug uptakes are found as 0.15 and 0.18 mmol/g dry gel, respectively. The incorporation of beta-CD-UM comonomer into the gel slightly reduces the methyl orange and salicylic acid releases. However, a significant enhancement was achieved in the case of sulfathiazole delivery. It can be concluded that the inclusion complex formation capability of beta-CD moiety increases the drug release by improving the aqueous solubility of hydrophobic drugs. On the other hand, in the case of hydrophilic drugs, the drug release retards by forming strong drug-beta-CD complex and reducing the drug diffusivity. (C) 2008 Wiley Periodicals, Inc.Publication Metadata only Intrinsic factor and vitamin B12 complex-loaded poly[lactic-co-(glycolic acid)] microspheres: preparation, characterization and drug release(WILEY, 2008) OGAN, AYŞE; Demir, Serap; Ogan, Ayse; Kayaman-Apohan, NilhanBACKGROUND: Vitamin B12 is an essential vitamin required by all mammals. Absorption of vitamin B12 is facilitated by binding of intrinsic factor-vitamin B12 complex to specific receptors in the ileum. In humans a deficiency of this vitamin or a lack of intrinsic factor leads to pernicious anaemia. The major objective of the present study was to prepare intrinsic factor-vitamin B12 complex-loaded poly[lactic-co-(glycolic acid)] (PLGA)-based microparticles and to investigate their release kinetics. RESULTS: PLGA copolymer was synthesized by the ring-opening polymerization method and characterized using gel permeation chromatography, Fourier transform infrared spectroscopy and H-1 NMR. The glass transition temperature measurement showed a single T-g at 40 degrees C. The intrinsic factor-vitamin B12 complex-loaded PLGA microspheres were prepared by a water-in-oil-in-water double emulsion solvent extraction/evaporation technique. An environmental scanning electron microscopy investigation demonstrated that the PLGA particles had a mean particle diameter of 38 gm. Interestingly, different drug release patterns (bi- and triphasic ones) were observed for vitamin B12-loaded and intrinsic factor-vitamin B12 complex-loaded microspheres. In contrast to the rapid release of vitamin B12 by itself, in vitro release tests showed that intrinsic factor and vitamin B12 in the complex were released from PLGA microspheres in a sustained manner over 15 days. CONCLUSION: PLGA microspheres can be an effective carrier for the intrinsic factor-vitamin B12 complex. (C) 2007 Society of Chemical Industry.