Person: DEMİR, SERAP
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DEMİR
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SERAP
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Publication Open Access In vitro and in silico investigation of inhibitory activities of 3-arylcoumarins and 3-phenylazo-4-hydroxycoumarin on MAO isoenzymes(2022-11-01) DANIŞ, ÖZKAN; DEMİR, SERAP; ERDEM, SAFİYE; OGAN, AYŞE; Yuce-Dursun B., DANIŞ Ö., Ozalp L., Sahin E., DEMİR S., ERDEM S., OGAN A.A series of 3-aryl coumarin derivatives and 3-phenylazo-4-hydroxycoumarin were evaluated for their monoamine oxidase (MAO) A and B inhibitory activity and selectivity by fluorometric enzymological assays. Among 21 coumarin derivatives, compound 21 (3-phenylazo-4-hydroxycoumarin) displayed a good inhibitory activity (0.12 +/- 0.02 mu M) and very high selectivity for MAO-B (SI > 833.33). The inhibition was determined as mixed-type and not time-dependent. Docking studies, molecular dynamics and molecular mechanics/Poisson-Boltzmann surface area (MM/PBSA) calculations were performed to elucidate in vitro results. Our results reveal that the insertion of an azo linker between coumarin and phenyl rings in 3-arylcoumarins enhances MAO-B selectivity enormously since such a linker leads to the perfect alignment of the coumarin ring in the aromatic cage and the phenyl ring in the entrance cavity of MAO-B active site. Hydrogen bond interactions with Cys172 in the active site entrance of MAO-B also contributes to the remarkably higher inhibitory activity and selectivity for MAO-B.Publication Open Access Immobilization of acetylcholinesterase onto pyrrole-containing photocured thermosets(2023-04-01) DEMİR, SERAP; ÇAKMAKÇI, EMRAH; OGAN, AYŞE; ALI K. K., DEMİR S., ÇAKMAKÇI E., OGAN A.Acetylcholinesterase (AChE; EC 3.1.1.7) is a group of enzymes that catalyzes the hydrolysis of the neurotransmitter acetylcholine (ACh) into choline and acetate. AChE inhibition is commonly utilized as a biomarker for pesticides. In membrane based AChE biosensors the enzyme immobilization onto an electrode surface is of prime importance. In previous studies, conducting polymers-based supports have been used for the immobilization of AChE. In this study, a novel immobilization platform was developed. The simultaneous polymerization of pyrrole and functional thiol/ene monomers was performed to prepare conductive thermosets. AchE was covalently immobilized onto the membranes through the epoxy functional groups. After the immobilization process, the optimal temperature increased to 50 °C, displaying a better thermal stability and the optimum pH was elevated to 8.5. The activity of the immobilized enzyme was tested in the presence of several metals, and it was found that Cu2+ ions caused a noticable inhibition. After 10 cycles, the immobilized enzyme retained 51% of its original activity. In accordance with our results; the durability and the stability of the immobilized enzyme were improved. In future studies, the method applied here can be used in the design of an AchE biosensor.Publication Open Access Covalent immobilization of acetylcholinesterase on a novel polyacrylic acid-based nanofiber membrane(WILEY, 2018-04) OGAN, AYŞE; Cakiroglu, Bekir; Cigil, Asli Beyler; Ogan, Ayse; Kahraman, M. Vezir; Demir, SerapIn this study, polyacrylic acid-based nanofiber (NF) membrane was prepared via electrospinning method. Acetylcholinesterase (AChE) from Electrophorus electricus was covalently immobilized onto polyacrylic acid-based NF membrane by demonstrating efficient enzyme immobilization, and immobilization capacity of polymer membranes was found to be 0.4 mg/g. The novel NF membrane was synthesized via thermally activated surface reconstruction, and activation with carbonyldiimidazole upon electrospinning. The morphology of the polyacrylic acid-based membrane was investigated by scanning electron microscopy, Fourier Transform Infrared Spectroscopy, and thermogravimetric analysis. The effect of temperature and pH on enzyme activity was investigated and maxima activities for free and immobilized enzyme were observed at 30 and 35 degrees C, and pH 7.4 and 8.0, respectively. The effect of 1 mM Mn2+, Ni2+, Cu2+, Zn2+, Mg2+, Ca2+ ions on the stability of the immobilized AChE was also investigated. According to the Michaelis-Menten plot, AChE possessed a lower affinity to acetylthiocholine iodide after immobilization, and the Michaelis-Menten constant of immobilized and free AChE were found to be 0.5008 and 0.4733 mM, respectively. The immobilized AChE demonstrated satisfactory reusability, and even after 10 consecutive activity assay runs, AChE maintained ca. 87% of its initial activity. Free enzyme lost its activity completely within 60 days, while the immobilized enzyme retained approximately 70% of the initial activity under the same storage time. The favorable reusability of immobilized AChE enables the support to be employable to develop the AChE-based biosensors.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 Open Access Preparation and characterization of hybrid nanomaterials containing magnetic fe3o4 nanoparticles as drug delivery system(2022-09-01) DEMİR, SERAP; Demir S.In this study, magnetic Fe3O4 nanoparticles were synthesized and the magnetic surfaces of the nanoparticles were modified with thiol groups. The chitosan polymer was modified with allyl groups and then bound to magnetic nanoparticles by the thiol-en click reaction. The drugs paclitaxel (PTX) and doxorubicin (DOX) were loaded separately and together into this prepared hybrid material, and then drug releases from the hybrid material were studied. The aim of this paper is to present the results on the controlled release of DOX and PPT cancer drugs from chitosan-Fe3O4 nanoparticles at two different pH values (5.0 and 7.4). PTX was effectively loaded into chitosan-Fe3O4 nanoparticles and slowly released up to 72.66% at pH 5 and 41.45% at pH 7.4 after 48 hours. DOX was effectively loaded into chitosan-Fe3O4 nanoparticles and slowly released up to 30.5% at pH 5 and 23.3% at pH 7.4 after 48 hours.Publication Open Access Design, synthesis and biological evaluation of novel benzocoumarin derivatives as potent inhibitors of MAO-B activity(2024-11-15) MELETLİ, FURKAN; DEMİR, SERAP; DANIŞ, ÖZKAN; MELETLİ F., Gündüz C., Alparslan M. M., ATTAR A., DEMİR S., İskit E., DANIŞ Ö.The continued research of novel reversible inhibitors targeting monoamine oxidase (MAO) B remains crucial for effectively symptomatic treatment of Parkinson\"s disease. In this study we synthesized and evaluated a new series of 3-aryl benzo[g] and benzo[h] coumarin derivatives as MAO-B inhibitors. Compound A6 has been found to display the most potent inhibitory activity and selectivity against the MAO-B isoform (IC50 = 13 nM and SI = >7693.31 respectively). Inhibition mode of A6 on MAO-B was predicted as mixed reversible inhibition with a Ki value of 3.274 nM. Furthermore, in order to elaborate structure–activity relationships, the binding mode of A6 was investigated by molecular docking simulations.