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DEMİR, SERAP

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Author: OGAN, AYŞE × Subject: SURFACE ×

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Now showing 1 - 2 of 2
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    PublicationOpen 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, Serap
    In 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.
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    Amine functional magnetic nanoparticles via waterborne thiol-ene suspension photopolymerization for antibody immobilization
    (ELSEVIER SCIENCE BV, 2018) OGAN, AYŞE; Muhsir, Pelin; Cakmakci, Emrah; Demir, Serap; Ogan, Ayse
    The modification of magnetic nanoparticles (MNPs) via different routes for biomolecule binding is an attractive area of research. Waterborne thiol-ene suspension photopolymerization (TESP) can be a useful method for preparing functional MNPs. In this study, for the very first time waterborne TESP was performed in the presence of MNPs. Neat MNPs were coated and in situ functionalized with amine groups by using thiol-ene chemistry. Engrailed-2 (EN2) protein, a potential biomarker for various cancers such as prostate cancer, bladder cancer, breast cancer and ovarian cancer, is known to be a strong binder to a specific DNA sequence (50-TAATTA-30) to regulate transcription. Anti-EN2 antibodies were immobilized onto these MNPs by physical adsorption and covalent bonding methods, respectively. The amount of the physically immobilized antibodies (0.54 mg/g) were found to be lower than the loading of the covalently bonded antibodies (1.775 mg/g). The biomarker level in the artificial solutions prepared was determined by enzyme-linked immunosorbent assay. Coated MNPs were characterized by FTIR, TGA, SEM and STEM. After TESP, the average diameter of the neat magnetite nanoparticles increased from similar to 15 nm to similar to 32 nm.