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Öğe Amperometric immunosensor developed for sensitive detection of SARS-CoV-2 spike S1 protein in combined with portable device(Elsevier, 2022) Erdem, Arzum; Senturk, Huseyin; Yildiz, Esma; Maral, MeltemIn this present study, an amperometric immunosensor was developed based on disposable screen-printed carbon electrode (SPCE) for specific and sensitive detection of SARS-CoV-2 S1 protein. Anti-SARS-CoV-2 S1 monoclonal antibody was firstly immobilized onto the electrode surface. Then, the sandwich complex was formed by addition of S1 protein, secondary antibody and HRP-IgG, respectively. Chronoamperometry measurements were done in the presence of TMB mediator and the detection of SARS-CoV-2 S1 protein was performed by using 10 mu L sample. The limit of detection (LOD) was found to be 0.19 ng/mL (equals to 24.7 amol in 10 mu L sample) in the linear range of 0.5-10 ng/mL obtained in buffer medium. The applicability of this assay was investigated in the linear range of 0.5-3 ng/mL S1 protein in artificial saliva medium with the LOD as 0.13 ng/mL (equals to 16.9 amol in 10 mu L sample). The selectivity study was examined in the presence of Hemagglutinin antigen (HA) in both mediums; buffer and artificial saliva while resulting with the successful discrimination between S1 protein and HA. The one of ultimate goals of our study is to present the possible implementation of this assay to point of care (POC) analysis. Under this aim, this assay was performed in combination with a portable device that is the commercial electrochemical analyzer. Amperometric detection of S1 protein in the range of 0.5-5 ng/mL was also successfully performed in artificial saliva medium with a resulting LOD as 0.15 ng/mL (equals to 19.5 amol in 10 mu L sample). In addition, a selectivity study was similarly carried out by portable device.Öğe Diagnostic kit based on halloysite nanoclay-ionic liquid nanocomposite modified electrode for electrochemical determination of cancer biomarker(Elsevier, 2023) Yildiz, Esma; Yurdacan, Beste; Erac, Yasemin; Erdem, ArzumNucleic acid hybridization is occurred between the selective single-stranded nucleic acid sequence and its target sequence, which is one of the essential procedure for electrochemical detection of nucleic acid. microRNA-21 (miRNA-21) is known as a biomarker in various cancers. The determination of miRNA-21 was attained through by hybridization of inosine substituted miRNA-21 specific DNA probe (Pinosine) with its target miRNA-21. In this study, the surface of pencil graphite electrode (PGE) was firstly modified with halloysite nanoclay-ionic liquid (HNT/IL) nanocomposite. The characterization of surface was performed by Scanning Electron Microscope (SEM) images and Energy Dispersive X-Ray Analysis (EDX) analysis, and the differences at surface modifications were also shown by electrochemical methods with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). For sensitive and selective determination of miRNA-21, Pinosine and target miRNA concen-tration, immobilization and hybridization time were optimized by using HNT/IL modified PGE in combination with differential pulse voltammetry (DPV). The detection limit was achieved as 0.17 mu g/mL (equals to 23.69 nM) in the linear range of 0.25-2 mu g/mL miRNA-21. The selectivity of voltammetric method based on HNT/IL-PGE developed for miRNA-21 was examined in the presence of mismatch (MM) and non-complementary (NC) se-quences. Because miRNA-21 is over-expressed in cancer cells, it has been tested in total RNA samples isolated from cancer cell line (breast cancer cell line, MCF-7). In the total RNA samples obtained from MCF-7, the detection limit was calculated as 0.28 mu g/mL in the linear range of 1-4 mu g/mL. Besides, the healthy cell line (human embryonic kidney cell line, HEK-293) was used as a control group and the results obtained by MCF-7 total RNA samples were compared to the results using HEK-293 total RNA samples in terms of miRNA-21 level.Öğe Impedimetric Detection Based on Label-Free Immunoassay Developed for Targeting Spike S1 Protein of SARS-CoV-2(Mdpi, 2022) Erdem, Arzum; Senturk, Huseyin; Yildiz, Esma; Maral, MeltemAfter the COVID-19 pandemic started all over the world, great importance was placed on the development of sensitive and selective bioanalytical assays for the rapid detection of the highly pathogenic SARS-CoV-2 virus causing COVID-19 disease. In this present work, an impedimetric immunosensor was developed and applied for rapid, reliable, sensitive and selective detection of the SARS-CoV-2 S1 protein. To detect the SARS-CoV-2 virus, targeting of the spike S1 protein was achieved herein by using S1 protein-specific capture antibody (Cab-S1) immobilized screen-printed electrode (SPE) in combination with the electrochemical impedance spectroscopy (EIS) technique. With the impedimetric immunosensor, the detection limit for S1 protein in buffer medium was found to be 0.23 ng/mL (equal to 23.92 amol in 8 mu L sample) in the linear concentration range of S1 protein from 0.5 to 10 ng/mL. In the artificial saliva medium, it was found to be 0.09 ng/mL (equals to 9.36 amol in 8 mu L sample) in the linear concentration range of S1 protein between 0.1 and 1 ng/mL. The selectivity of the impedimetric immunosensor toward S1 protein was tested against influenza hemagglutinin antigen (HA) in the buffer medium as well as in artificial saliva.Öğe Optimized aptamer-based next generation biosensor for the ultra-sensitive determination of SARS-CoV-2 S1 protein in saliva samples(Wiley, 2024) Erdem, Arzum; Senturk, Huseyin; Yildiz, Esma; Maral, MeltemCOVID-19 is an infectious disease caused by the SARS-CoV-2 virus, which rapidly spread worldwide and resulted in a pandemic. Efficient and sensitive detection techniques have been devised since the onset of the epidemic and continue to be improved at present. Due to the crucial role of the SARS-CoV-2 S1 protein in facilitating the virus's entry into cells, efforts in detection and treatment have primarily centered upon this protein. In this study, a rapid, ultrasensitive, disposable, easy-to-use, cost-effective next generation biosensor based on optimized aptamer (Optimer, OPT) was developed by using a disposable pencil graphite electrode (PGE) and applied for the impedimetric determination of SARS-CoV-2 S1 protein. The S1 protein interacted with the OPT in the solution phase and then immobilized onto the PGE surface. Subsequently, measurements using electrochemical impedance spectroscopy (EIS) were conducted in a solution containing a redox probe of 1 mM [Fe(CN)6]3- /4- . Under optimum conditions, the limit of detection (LOD) for the S1 protein in buffer medium at concentrations ranging from 101 to 106 ag/mL was calculated as 8.80 ag/mL (0.11 aM). The selectivity of the developed biosensor was studied against MERS-CoV-S1 protein (MERS) and Influenza Hemagglutinin antigen (HA). Furthermore, the application of the biosensor in artificial saliva medium is demonstrated. The LOD was also calculated in artificial saliva medium in the concentration range of 101-105 ag/mL and calculated as 2.01 ag/mL (0.025 aM). This medium was also used to assess the selectivity of optimized-aptamer based biosensor.Öğe Recent developments in wearable biosensors for healthcare and biomedical applications(Elsevier Sci Ltd, 2024) Erdem, Arzum; Eksin, Ece; Senturk, Huseyin; Yildiz, Esma; Maral, MeltemMinimizing biosensor designs and creating wearable sensor designs are newly-emerging and the most interesting research topics of recent years. By the advantages of wearable biosensors, sensitive and selective non-invasive analysis of various analytes can be successfully performed simultaneously with wireless systems, without long and laborious steps. Real-time monitoring is possible for a wide range of physiological signals, including physical bio-signals like temperature, pulse, and blood pressure, as well as biochemical parameters like glucose, dopamine, ions, and many other biomarkers in human biofluids including sweat, saliva, interstitial fluid, and tears. Continuous monitoring of physiological and personal parameters through wearable sensors has been demonstrated to define the user's well-being, comfort, and health status for all at all ages in life environments, both indoor and outdoor. Therefore, research sciences and biomedical societies have recently started to use wearable biosensors to assess precise health diagnosis. In this review, we outline the most recent notable accomplishments achieved within the domain of wearable sensors for biomedical and healthcare applications, involving biomultifunctional smart wearable sensors, wearable devices, decision-making units, existing state of the market, challenges, and upcoming patterns of wearable devices.Öğe Schiff Base-platinum and ruthenium complexes and anti-Alzheimer properties(Elsevier Scince Inc, 2024) Gunnaz, Salih; Yildiz, Esma; Tuncel Oral, Ayca; Yurt, Fatma; Erdem, Arzum; Irisli, SevilThis study investigates the effects of Pt and Ru complexes containing a Schiff base with a diimine structure on Alzheimer's disease. The Schiff base (N1E,N2E)-N1,N2-bis(isoquinolin-4-ylmethylene)benzene-1,2-diamine (I) and the novel Pt(II) and Ru(II) complexes (Ia and Ib) were synthesized and characterized using FTIR, NMR (1H, 13C), mass spectrometry, and elemental analyses. Their ability to inhibit amyloid beta (A beta 1-42) aggregation was determined in vitro using the SH-SY5Y cell line. Fluorescence spectroscopy investigated the early aggregation kinetics and dose-dependent characteristics of A beta 1-42 with the complexes. Transmission electron microscopy confirmed the results. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and 1H NMR spectroscopy examined the interaction with A beta 1-16. Electrochemical analysis using square wave voltammetry monitored the interaction with A beta 1-42. The synthesized complexes were active in inhibiting amyloid aggregation at a low molar ratio.Öğe Synthesis and characterization of polysaccharide-cryogel and its application to the electrochemical detection of DNA(Springer Wien, 2024) Tunca, Nilay; Maral, Meltem; Yildiz, Esma; Sengel, Sultan Butun; Erdem, ArzumThe main goal of our study is to demonstrate the applicability of the PPy-cryogel-modified electrodes for electrochemical detection of DNA. First, a polysaccharide-based cryogel was synthesized. This cryogel was then used as a template for chemical polypyrrole synthesis. This prepared polysaccharide-based conductive cryogel was used for electrochemical biosensing on DNA. Carrageenan (CG) and sodium alginate (SA) polysaccharides, which stand out as biocompatible materials, were used in cryogel synthesis. Electron transfer was accelerated by polypyrrole (PPy) synthesized in cryogel networks. A 2B pencil graphite electrode with a diameter of 2.00 mm was used as a working electrode. The prepared polysaccharide solution was dropped onto a working electrode as a support material to improve the immobilization capacity of biomolecules and frozen to complete the cryogelation step. PPy synthesis was performed on the electrodes whose cryogelation process was completed. In addition, the structures of cryogels synthesized on the electrode surface were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Surface characterization of the modified electrodes was performed by energy-dispersive X-ray spectroscopy (EDX) analysis. Electrochemical determination of fish sperm DNA (fsDNA) was performed using a PPy-cryogel-modified electrode. The use of a porous 3D cryogel intermediate material enhanced the signal by providing a large surface area for the synthesis of PPy and increasing the biomolecule immobilization capacity. The detection limit was 0.98 mu g mL(-1) in the fsDNA concentration range 2.5-20 mu g mL(-1). The sensitivity of the DNA biosensor was estimated to 14.8 mu A mM(-1) cm(-2). The stability of the biosensor under certain storage conditions was examined and observed to remain 66.95% up to 45 days.Öğe The targeted photodynamic therapy of breast cancer with novel AS1411-indium(III) phthalocyanine conjugates(Elsevier, 2024) Akkus, Nurefsan; Eksin, Ece; Sahin, Gamze; Yildiz, Esma; Bagda, Efkan; Altun, Ahmet; Bagda, EsraIn the study, the novel indium(III) phthalocyanines containing 4-mercaptopyridine groups as substituents on the peripheral (Pc3) or non-peripheral (Pc8) tetra-and peripheral octa (Pc13) positions were synthesized. After then, the synthesized phthalocyanines were converted to their water-soluble derivatives that are Pc5, Pc10, and Pc15 by the quaternization of the nitrogen atoms on the substituents. These new phthalocyanines have been characterized by various spectroscopic methods such as FT-IR, 1H-NMR, elemental analysis, UV-vis, MALDI-TOF mass spectra. Photochemical properties were also investigated for the synthesized phthalocyanines. In this study; quaternized derivatives were studied in DMSO and aqueous solutions, while non-quaternized derivatives were studied only in DMSO. The interaction between AS1411 and three phthalocyanines (Pc5, Pc10, and Pc15) was investigated using spectroscopic methods and electrochemical impedance spectroscopy technique combined with pencil graphite electrodes (PGEs). The cytotoxic activity of AS1411 and each phthalocyanine was investigated in the MCF-7 and doxorubicin (Dox) resistant MCF-7/DOX-R cell lines in the presence and absence of Dox. The photodynamic therapy (PDT) activity of Pc5, Pc10, and Pc15 and their AS1411 conjugates was investigated on MCF-7, MCF-7/DOX-R and MCF-10A cells. The IC50 values for MCF-7 cells were found as 1.1, 0.46, and 0.46 mM for Pc5 and 0.58, 0.34, and 0.32 mM for Pc5-AS1411 conjugate in the absence of irradiation and radiation with 7 J and 20 J. The values for MCF-7/DOX-R cells were found 0.81, 0.30, and 0.11 mM for Pc5 and 0.39, 0.12, and 0.15 mM for Pc5-AS1411 conjugate without irradiation and radiation with 7 J and 20 J, respectively. Apoptosis and cell imaging studies showed that conjugation of the phthalocyanines with AS1411 induced apoptosis in both cell lines and increases the intracellular entry of phthalocyanine Pc5.Öğe Voltammetric detection of miRNA hybridization based on electroactive indicator-cobalt phenanthroline(Elsevier, 2020) Erdem, Arzum; Eksin, Ece; Kadikoylu, Gulce; Yildiz, EsmaThe indicator-based nucleic acid detection protocol is one of the major approaches to monitor the sequence selective nucleic acid hybridization-mediated recognition events in biochemical analysis. the metal complex, cobalt phenanthroline, [Co(phen)(3)(3+)], which is one of the electroactive indicators, interacts more with double stranded nucleic acids via intercalation. Thus, this interaction permits an increase at the electrochemical signal of [Co(phen)(3)(3+)]. in our study, the interaction of metal complex, [Co(phen)(3)(3+)] with nucleic acids was examined using pencil graphite electrodes (PGEs) in combination with differential pulse voltammetry (DPV) technique. the voltammetric detection of miRNA-34a was investigated based on the changes at the electrochemical signal of [Co(phen)(3)(3+)] under optimized experimental conditions; such as accumulation potentialof metal complex and DNA probe concentration, hybridization time, target miRNA concentration. Furthermore, the selectivity of electrochemical miRNA-34a biosensor was studied in contrast to different miRNAs. the applicability of indicator-based biosensor specific to miRNA-34a was also presented by using total RNA samples. (C) 2020 Elsevier B.V. All rights reserved.
