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Öğe A label-free electrochemical biosensor for highly sensitive detection of GM2A based on gold nanoparticles/conducting amino-functionalized thiophene polymer layer(Elsevier Science Sa, 2023) Aydin, Elif Burcu; Aydin, Muhammet; Sezginturk, Mustafa KemalIn this study, a new immunosensor based on an indium tin oxide (ITO) substrate functionalized with gold nanoparticles (GNPs)/amino-functionalized thiophene polymer P(ThiAmn) multilayer was fabricated for impedimetric determination of GM2 activator protein (GM2A). To engineer the biosensor, a relatively simple approach composed of GNPs electrodeposition and ThiAmn electropolymerization was utilized. The use of GNPs and P(ThiAmn) increased the substrate surface area, which was beneficial to immobilize a large amount of antiGM2A biorecognition elements. The designed bifunctional layer served as a promising matrix material and provided an innovative sensor fabrication. Electrochemical techniques were employed to investigate the specific immuno-interaction process between biorecognition anti-GM2A antibodies and GM2A antigens. Apart from these techniques, spectral techniques were utilized for the characterization of different modified electrode surfaces. Under optimum conditions, GM2A was determined in a linear concentration range from 0.0185 to 111 pg/mL with a detection limit (LOD) of 5.8 fg/mL by electrochemical impedance spectroscopy (EIS) technique. This biosensor exhibited good reproducibility, long storage-stability, and excellent specificity for GM2A antigens. Additionally, this immunosensor was applied to quantify GM2A in commercial serum samples, and satisfactory results were obtained.Öğe A new immunosensing platform based on conjugated Poly(ThidEp-co-EDOT) copolymer for resistin detection, a new obesity biomarker(Springer Wien, 2024) Aydin, Elif Burcu; Aydin, Muhammet; Sezginturk, Mustafa KemalThe design of a novel electrochemical impedimetric biosensor for label-free analysis of resistin, a biomarker for obesity, is reported. For the fabrication of the immunosensor, a novel approach composed of electrochemical copolymerization of double epoxy groups-substituted thiophene (ThidEp) and 3,4-Ethylenedioxythiophene (EDOT) monomers was utilized. Anti-resistin antibodies were covalently attached to the copolymer-coated electrode. The capture of resistin antigens by anti-resistin antibodies caused significant variations in charge transfer resistance (R-ct) because of the immunoreactions between these proteins. Under optimum experimental variables, the changes in impedance signals were employed for the determination of resistin antigen concentration, and the prepared immunosensor based on conjugated copolymer illustrated a wide linear range between 0.0125 and 22.5 pg/mL, a low detection limit (LOD) of 3.71 fg/mL, and a good sensitivity of 1.22 k Omega pg(-1)mL cm(2). The excellent analytical performance of the resistin immunosensor in terms of selectivity, sensitivity, repeatability, reproducibility, storage stability, and low detection limit might be attributed to the conductive copolymer film layer generation on the disposable indium tin oxide (ITO) platform. The capability of this system for the determination of resistin in human serum and saliva samples was also tested. The immunosensor results were in accordance with the enzyme-linked immunosorbent assay (ELISA) results. The matrix effects of human serum and saliva were also investigated, and the proposed immunosensor displayed good recovery ranging from 95.91 to 106.25%. The engineered immunosensor could open new avenues for obesity monitoring.Öğe A novel electrochemical impedance immunosensor for the quantification of CYFRA 21-1 in human serum(Springer Wien, 2023) Aydin, Elif Burcu; Aydin, Muhammet; Sezginturk, Mustafa KemalA sensitive, simple, and reliable immunosensor was constructed to detect the lowest alteration of a fragment of cytokeratin subunit 19 (CYFRA 21-1), a protein lung carcinoma biomarker. The proposed immunosensor was manufactured with a carbon black C45/polythiophene polymer-containing amino terminal groups (C45-PTNH2) conductive nanocomposite, resulting in an excellent, biocompatible, low-cost, and electrically conductive electrode surface. Anti-CYFRA 21-1 biorecognition molecules were attached to the electrode thanks to the amino terminal groups of the used PTNH2 polymer with a relatively simple procedure. All electrode surfaces after modifications were characterized by electrochemical, chemical, and microscopic techniques. Electrochemical impedance spectroscopy (EIS) was also utilized for the evaluation of the analytical feature of the immunosensor. The charge transfer resistance of the immunosensor signal was correlated with the CYFRA 21-1 concentration in the concentration range 0.03 to 90 pg/mL. The limit of detection (LOD) and the limit of quantification (LOQ) of the suggested system were 4.7 fg/mL and 14.1 fg/mL, respectively. The proposed biosensor had favorable repeatability and reproducibility, long storage stability, excellent selectivity, and low cost. Furthermore, it was applied to determine CYFRA 21-1 in commercial serum samples, and satisfactory recovery results (98.63-106.18%) were obtained. Thus, this immunosensor can be offered for clinical purposes as a rapid, stable, low-cost, selective, reproducible, and reusable tool.Öğe An innovative method for the detection of alpha synuclein, a potential biomarker of Parkinson's disease: quartz tuning fork-based mass sensitive immunosensor design(Royal Soc Chemistry, 2024) Karaboga, Muenteha Nur Sonuc; Unal, Mehmet Altay; Ari, Fikret; Sezginturk, Mustafa Kemal; Ozkan, Sibel AysilAn innovative biosensing fabrication strategy has been demonstrated for the first time using a quartz tuning fork (QTF) to develop a practical immunosensor for sensitive, selective and practical analysis of alpha synuclein protein (SYN alpha), a potential biomarker of Parkinson's disease. Functionalization of gold-coated QTFs was carried out in 2 steps by forming a self-assembled monolayer with 4-aminothiophenol (4-ATP) and conjugation of gold nanoparticles (AuNPs). The selective determination range for SYN alpha of the developed biosensor system is 1-500 ng mL-1 in accordance with the resonance frequency shifts associated with a limit of detection of 0.098 ng mL-1. The changes in surface morphology and elemental composition were evaluated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX). The remarkable point of the study is that this QTF based mass sensitive biosensor system can capture the SYN alpha target protein in cerebrospinal fluid (CSF) samples with recoveries ranging from 92% to 104%. An innovative biosensing fabrication strategy has been demonstrated for the first time using a quartz tuning fork to develop a practical immunosensor for sensitive, selective and practical analysis of alpha synuclein protein.Öğe Biosensors for saliva biomarkers(Elsevier Academic Press Inc, 2023) Aydin, Elif Burcu; Aydin, Muhammet; Sezginturk, Mustafa KemalThe analysis of salivary biomarkers has gained interest and is advantageous for simple, safe, and non-invasive testing in diagnosis as well as treatment. This chapter explores the importance of saliva biomarkers and summarizes recent advances in biosensor fabrication. The identification of diagnostic, prognostic and therapeutic markers in this matrix enables more rapid and frequent testing when combined with the use of biosensor technology. Challenges and future goals are highlighted and examined.Öğe Carboxyethylsilanetriol-Coated Magnetic Nanoparticles as an Ultrasensitive Immunoplatform for Electrochemical Magnetosensing of Cotinine(Amer Chemical Soc, 2024) Aydin, Muhammet; Aydin, Elif Burcu; Sezginturk, Mustafa KemalIn the present study, an innovative and simple electrochemical magneto biosensor based on carboxyethylsilanetriol-modified iron oxide (Fe3O4) magnetic nanoparticles was designed for ultrasensitive and specific analysis of cotinine, an important marker of smoking. Anticotinine antibodies were covalently immobilized on carboxylic acid-modified magnetic nanoparticles, and the cotinine-specific magnetic nanoparticles created a specific surface on the working electrode surface. The use of magnetic nanoparticles as an immobilization platform for antibodies provided a large surface area for antibody attachment and increased sensitivity. In addition, the advantages of the new immobilization platform were reusing the working electrode numerous times, recording repeatable and reproducible signals, and reducing the necessary volume of biomolecules. The specific interaction between cotinine and cotinine-specific antibody-attached magnetic nanoparticles restricted the electron transfer of the redox probe and changed the impedimetric response of the electrode correlated to the concentration of cotinine. The magneto biosensor had a wide detection range (2-300 pg/mL), a low LOD (606 fg/mL), and an acceptable recovery (97.24-105.31%) in real samples. In addition, the current biosensor's measurement results were in good agreement with those found by the standard liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA) methods. These results showed that a simple impedimetric immunosensing platform was generated for the cotinine analysis.Öğe Fabrication of a highly sensitive conductive copolymer layer modified immunosensing tool for cytokeratin-19 fragment detection(Elsevier, 2024) Aydin, Elif Burcu; Aydin, Muhammet; Sezginturk, Mustafa KemalDesign of a new and highly selective impedimetric biosensor based on the immobilization of a fragment of cytokeratin subunit 19 (CYFRA 21-1)-specific antibodies onto a conductive copolymer layer (poly(epoxy-substituted thiophene)-co-poly(3,4-ethylenedioxythiophene), CCL)-coated indium tin oxide (ITO) for the determination of CYFRA 21-1 in serum samples was reported. CCL was applied as a working electrode-modifying reagent to prepare the surface of the working ITO electrode, and CYFRA 21-1-specific antibodies bound to epoxy ends present in the copolymer layer matrix. The impedimetric response of the immunosensor to CYFRA 21-1 was recorded, and the signaling mechanism of the suggested immunosensor was based on an increase in the charge transfer resistance in the presence of target CYFRA 21-1. The developed biosensor exhibited excellent selectivity for CYFRA 21-1, and it could detect CYFRA 21-1 in a linear dynamic range from 0.0125 to 35 pg/mL with a limit of quantification (LOQ) of 12.25 fg/mL. The designed biosensor showed good storage stability, high sensitivity, suitable repeatability and reproducibility, and acceptable long-term stability. The clinical analysis of the manufactured immunosensor was explored for the analysis of serum samples, and high recoveries and good relative standard deviations (RSDs) were obtained in the range of 97.01 and 103.17 %, respectively. This copolymer-based biosensor could be a feasible tool for clinical diagnosis in complex serum samples.Öğe Fluid-based wearable sensors: a turning point in personalized healthcare(Tubitak Scientific & Technological Research Council Turkey, 2023) Vural, Berin; Uludag, Inci; Ince, Bahar; Ozyurt, Canan; Ozturk, Funda; Sezginturk, Mustafa KemalNowadays, it has become very popular to develop wearable devices that can monitor biomarkers to analyze the health status of the human body more comprehensively and accurately. Wearable sensors, specially designed for home care services, show great promise with their ease of use, especially during pandemic periods. Scientists have conducted many innovative studies on new wearable sensors that can noninvasively and simultaneously monitor biochemical indicators in body fluids for disease prediction, diagnosis, and management. Using noninvasive electrochemical sensors, biomarkers can be detected in tears, saliva, perspiration, and skin interstitial fluid (ISF). In this review, biofluids used for noninvasive wearable sensor detection under four main headings, saliva, sweat, tears, and ISF-based wearable sensors, were examined in detail. This report analyzes nearly 50 recent articles from 2017 to 2023. Based on current research, this review also discusses the evolution of wearable sensors, potential implementation challenges, and future prospects.Öğe Functionalized magnetic nanoparticles for electrochemical magneto biosensing of PSMA cancer biomarker(Royal Soc Chemistry, 2024) Aydin, Muhammet; Aydin, Elif Burcu; Sezginturk, Mustafa KemalA novel platform on which anti-prostate specific membrane antigen (PSMA) antibodies were immobilized on the core-shell structure of iron oxide (Fe3O4)/6-phosphonohexanoic acid (6Pha) nanoparticles was developed for the specific detection of PSMA. The Fe3O4@SiO2@6Pha nanoparticles were selected as an immune sensing platform, and external magnetic force provided separation of the target PSMA antigen in biological samples. The core-shell Fe3O4@SiO2@6Pha nanoparticles conjugated with anti-PSMA antibodies were utilized for PSMA concentration measurement. The analysis strategy was based on the direct binding of anti-PSMA antibodies to the target PSMA antigens. Different electrochemical analysis approaches were utilized to characterize the biosensing system. The differences in impedimetric signals before and after interaction with PSMA antigens were associated directly with the PSMA concentration. Under optimized conditions, the linear range of 7.5-1250 pg mL-1, the detection limit of 2.21 pg mL-1, and the quantification limit of 7.36 pg mL-1 were obtained. The applicability of the immunosensor was tested on diluted human serum samples, and satisfactory results were obtained. The results illustrate that a reliable, robust, selective, and simple detection strategy was developed for further clinical diagnosis. A novel platform on which anti-prostate specific membrane antigen (PSMA) antibodies were immobilized on the core-shell structure of iron oxide (Fe3O4)/6-phosphonohexanoic acid (6Pha) nanoparticles was developed for the specific detection of PSMA.Öğe Label-free and ultrasensitive electrochemical cotinine sensing based on bio-modified magnetic nanoparticles(Elsevier Science Sa, 2024) Aydin, Muhammet; Aydin, Elif Burcu; Sezginturk, Mustafa KemalHerein, a label-free impedimetric magneto-biosensor was constructed for detection of cotinine, a promising marker of active and passive smoking. Indium tin oxide sheet (ITO) was utilized as a working electrode and modified magnetic iron oxide (Fe3O4) nanoparticles were attached to the electrode with a neodium magnet. Magnetic iron oxide nanoparticles were modified with a conjugated carboxyl-functionalized poly(pyrrolepropionic acid) (PPPAc) polymer to increase the area and improve the conductivity, which were utilized to immobilize anticotinine antibodies. Anti-cotinine antibodies were specific recognition elements, and a selective sensing platform was constructed by covalent binding of anti-cotinine antibodies. The impedimetric signal was changed with a reaction between cotinine analytes and anti-cotinine antibodies, and the proposed biosensor demonstrated excellent sensitivity, with a wide linear range from 2 to 500 pg/mL and a low detection limit of 0.579 pg/mL. Additionally, this newly constructed magneto-biosensor demonstrated high sensitivity, good reproducibility, and superior specificity. In order to test clinical applicability, serum and saliva samples were analysed with the suggested biosensor, and it indicated excellent performance in comparison with the gold standard methods of enzyme-linked immunoassay (ELISA) and high-performance liquid chromatography (HPLC) systems for the analysis of cotinine. These results displayed that the immunosensor could be potentially useful for clinical diagnostics.Öğe Label-Free Electrochemical Immunosensor Based on Conjugated Polymer Film Coated Disposable Electrode for Ultrasensitive Determination of Resistin Potential Obesity Biomarker(Amer Chemical Soc, 2024) Aydin, Elif Burcu; Aydin, Muhammet; Sezginturk, Mustafa KemalA new label-free immunosensor was designed for sensitive detection of resistin obesity biomarker in human biological fluids. To construct a sensing interface, the monomer of double epoxy groups-substituted thiophene (TdiEpx) was synthesized for the fabrication of the biosensing system. A disposable indium tin oxide sheet was first modified by electrochemical polymerization of the TdiEpx monomer, and this robust and novel surface was characterized using different spectroscopic and electrochemical analyses. The double epoxy ends were linked to the amino ends of anti-resistin, and they served as binding points for the covalent binding of biomolecules. The double epoxy ends present in each TdiEpx monomer ensured an extensive surface area, which improved the quantity of attached anti-resistin. The determination of resistin antigen was based on the specific coupling of resistin with anti-resistin, and this interaction hindered the electron transfer reaction. The immunosensor introduced a wide linear range of 0.0125-15 pg/mL, a low detection limit of 4.17 fg/mL, and an excellent sensitivity of 1.38 kohm pg mL(-1) cm(2). In this study, a sandwich enzyme-linked immunosorbent assay spectrophotometric method was utilized as a reference technique for the quantitative analysis of resistin in human serum and saliva samples. Both measurements in clinical samples displayed correlations and high-correlation coefficients. In addition, this immunosensor had good storage stability, acceptable repeatability and reproducibility, high specificity, and good accuracy. The proposed immunosensor provided a simple and versatile impedimetric immunosensing platform and a promisingly sensitive way for clinical applications.Öğe Ultrasensitive detection of NSE employing a novel electrochemical immunosensor based on a conjugated copolymer(Royal Soc Chemistry, 2024) Aydin, Muhammet; Aydin, Elif Burcu; Sezginturk, Mustafa KemalIn the current study a simple and highly specific label-free impedimetric neuron specific enolase (NSE) immunosensor based on a copolymer matrix-coated disposable electrode was designed and tested. The copolymer matrix was prepared using a very conductive EDOT monomer and semi-conductive thiophene-bearing epoxy groups (ThEp), and the combination of the two monomers enhanced the conductivity and protein loading capacity of the electrode surface. The P(ThEp-co-EDOT) copolymer matrix was prepared via a drop-casting process and anti-NSE recognition biomolecules were immobilized directly on the epoxy groups of the copolymer. After the coupling of NSE molecules on the P(ThEp-co-EDOT) copolymer matrix-coated electrode surface, the charge transfer resistance (Rct) of the biosensor changed dramatically. These changes in Rct were proportional to the NSE molecule amounts captured by anti-NSE molecules. Under optimized experimental conditions, the increment in the Rct value was proportional to the NSE concentration over a range of 0.01 to 25 pg mL-1 with a detection limit (LOD) of 2.98 x 10-3 pg mL-1. This copolymer-coated electrode provided a lower LOD than the other biosensors. In addition, the suggested electrochemical immuno-platform showed good selectivity, superior reproducibility, long-term stability, and high recovery of NSE in real serum (95.64-102.20%) and saliva (95.28-105.35%) samples. These results showed that the present system had great potential for electrochemical biosensing applications. A P(ThEp-co-EDOT) copolymer matrix was synthesized and utilized as a platform to construct a new NSE biosensor.
