Yazar "Sezgintürk, Mustafa Kemal" seçeneğine göre listele

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    A comparison between LP(GMA) and CLP(GMA) polymer composites as an immobilization matrix for biosensing applications: A model immunosensor for IL 1?
    (Elsevier Science Bv, 2019) Aydin, Elif Burcu; Sezgintürk, Mustafa Kemal
    A comparative study was made by using two matrices (Linear poly(glycidyl methacrylate) (GMA) polymer (LP(GMA)) and carbon black-polyvinylidene fluoride (PVDF)-LP(GMA) composite CLP(GMA)) as immobilization platforms for anti-IL 1 alpha antibody on the development of impedimetric immunosensor for IL 1 alpha biomarker determination. These materials were spin coated onto the clean ITO electrode surface separately and used for IL 1 alpha immunosensor fabrication. Carbon black is utilized as a conductive material and has been employed over the last few decades for electrochemical biosensors development. The using of CLP(GMA) composite as an interface material shows fast electron transfer, when compared to LP(GMA) modified ITO electrode. This comparative study investigated the efficacy of carbon black for impedimetric biosensing. Anti-IL 1 alpha antibodies were utilized as bioreceptors and bound to epoxy groups of GMA polymer. For electrochemical characterizations, Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and Single Frequency Impedance methods were employed. Furthermore, to follow the antibody attachment on the modified ITO substrates, Fourier Transform Infrared Spectroscopy and Raman spectral techniques were utilized. The morphological characterizations of immunosensor construction stages were carried out by Scanning Electron Microscopy and Atomic Force Microscopy analyses. The sensitive and label-free technique of EIS was used for quantification of IL 1 alpha concentration. Under optimum experimental conditions, the immunosensor had a good linear relationship between impedance values and the IL 1 alpha concentrations ranging from 0.01 to 2 pg/mL and from 0.01 to 3 pg/mL for LP(GMA) and CLP(GMA) modified ITO electrodes, respectively. The results confirmed that CLP(GMA) used in the preparation of the immunosensor illustrated improvements in immunosensor performance, comparing to the LP(GMA) modified immunosensor. Additionally, the immunosensor was successfully applied to evaluate human serum and saliva samples. The obtained results from these samples illustrated the feasibility of the immunosensor for clinical diagnosis in complex biological samples. Also, a simple and low-cost approach was attempted for development of immunosensor with remarkable performance characteristics. (C) 2019 Elsevier B.V. All rights reserved.
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    A direct and simple immobilization route for immunosensors by CNBr activation for covalent attachment of anti-leptin: obesity diagnosis point of view
    (Springer Heidelberg, 2022) Uludag, Inci; Sezgintürk, Mustafa Kemal
    Leptin is a peptide hormone produced in adipose tissue that works as an antiobesity hormone by balancing energy intake and expenditure. We aimed to develop an ultrasensitive electrochemical immunosensor based on a novel immobilization technique for the early detection of leptin-related diseases in this work. Although several methods for immobilizing antibodies to the biosensor recognition element are known, it is necessary to utilize novel, cost-effective, and less complicated immobilization procedures. When compared with currently utilized immobilization techniques for leptin measurement, this novel method is more efficient, easy to prepare, and sensitive, with a broad detection range. Indium tin oxide-coated polyethylene terephthalate (ITO-PET) sheets were used as the working electrode. ITO-PET sheets were modified using cyanogen bromide (CNBr) to immobilize the anti-leptin antibody through covalent interactions. Each stage of the proposed biosensors was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods, and extensive characterization studies were carried out. The designed biosensor has a wide linear detection range (0.05-100 pg/mL), low limits of detection (LOD) (0.0086 pg/mL) and quantification (LOQ) (0.0287 pg/mL). It was concluded that although it is disposable, the ITO-PET working electrode retains its activity even in repeated studies. In addition, the new immobilization procedure provided by CNBr for the designed biosensor fabrication can be effectively used in other biosensing applications.
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    A disposable and ultrasensitive immunosensor for the detection of HE4 in human serum samples
    (Springer Int Publ Ag, 2024) Vural, Berfin; Çalışkan, Meltem; Bilgi Kamaç, Melike; Sezgintürk, Mustafa Kemal
    Ovarian cancer is described as excessive cell proliferation in the ovaries. It is thought that ovarian cancer and the human epididymis protein 4 (HE4) are closely linked. HE4 is approved as a critical biomarker for the diagnosis and the progression monitoring of the ovarian cancer. In this work, an impedimetric biosensor was fabricated for the analysis of HE4 by modifying the surface of disposable ITO-PET (indium tin oxide-polyethylene terephthalate) sheet with a certain dimensions by 3-Aminopropyl trimethoxy silane (3-APTES). For the interaction between the amino ends of 3-APTES and anti-HE4 antibodies glutaraldehyde was used as a cross-linker. Electrochemical impedance (EIS) and cyclic voltammetry (CV) methods were applied in all electrochemical measurements. Important optimization and characterization experiments have also been completed. Under the optimum conditions, the concentration range for HE4 was obtained between 1 pg/mL and 3000 pg/mL with an LOD and LOQ values of 0.094 pg/mL and 0.3134 pg/mL, respectively. Selectivity experiments revealed that the biosensor showed a great selectivity with its target HE4. The biosensor also showed a good reproducibility with a relative standard deviation (RSD) of slope data calculated as 2.443%. Finally, we applied the biosensor to the commercial real human serum samples for analysis of HE4 and the results of these experiments were encouraging to be used in clinical settings.
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    A disposable and ultrasensitive ITO based biosensor modified by 6-phosphonohexanoic acid for electrochemical sensing of IL-1? in human serum and saliva
    (Elsevier Science Bv, 2018) Aydin, Elif Burcu; Sezgintürk, Mustafa Kemal
    In this study, we constructed a new and sensitive ITO based electrochemical immunosensor for detection of interleukin 1 beta(IL-1 beta), a cancer biomarker found in serum and saliva. 6-phosphonohexanoic acid (PHA) was used as a biomolecule immobilization matrix for the first time. Anti-IL-1 beta antibody was utilized as a biorecognition molecule that immobilized onto carboxyl groups of 6-phosphohexanoic acid (PHA) via amide bond. Selective interaction between anti-IL-1 beta antibodies and IL-1 beta antigens was investigated by Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV) and Single Frequency Impedance (SFI) methods. The surface characterization of the immunosensor was performed by fourier transform infrared spectroscopy (FTIR), raman spectroscopy, scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) in order to illustrate individual steps of biosensor construction. Under the optimized experimental conditions, the change in impedance was proportional to IL-1 beta concentrations in the range of 0.025-3 pg/mL (R-2 = 0.99) with detection limit of 7.5 fg/mL. The reproducibility, repeatability, stability, and specificity of the developed immunosensor were analyzed. In addition, the developed immunosensor was successfully utilized for the determination of IL-1 beta in serum and saliva samples by using the standard addition method with recoveries of 96.7-105.4%. This immunosensor was applicable for the requirements of routine analysis with respect to performance, functionality and cost. (C) 2018 Elsevier B.V. All rights reserved.
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    A disposable biosensing system for analysis of CA125 in real human serum samples
    (Tubitak Scientific & Technological Research Council Turkey, 2025) Afşar, Meltem; Vural, Berfin; Bilgi Kamaç, Melike; Sezgintürk, Mustafa Kemal
    Several biomarkers have been developed to track the development of ovarian cancer and identify the illness at an early stage. A promising development for ovarian cancer is using cancer antigen 125 (CA125). The objective of this work is to identify the CA125 marker by utilizing an indium tin oxide polyethylene electrode. The advantage of the designed biosensor is that it is very cheap, disposable, practical, and easy to use. The necessary parameters for the developed biosensor have been optimized in detail. Repeatability, reproducibility, regeneration, storage, and selectivity studies have been completed to characterize the proposed biosensor. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were used for all experimental investigations of the proposed biosensor. The immunosensor offers a large linear detection range (0.01-100 pg/mL). Moreover, this developed sensor has a 0.018 pg/mL limit of detection and a 0.06 pg/mL limit of quantification. The high accuracy of this biosensor was observed in five commercial human serums.
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    A disposable immunosensor using ITO based electrode modified by a star-shaped polymer for analysis of tumor suppressor protein p53 in human serum
    (Elsevier Advanced Technology, 2018) Aydin, Muhammet; Aydin, Elif Burcu; Sezgintürk, Mustafa Kemal
    Label-free immunosensor based on tetra armed star-shaped poly(glycidylmethacrylate) (Star(PGMA)) modified disposable ITO electrode was developed for detection of p53 protein, an important colorectal cancer biomarker. This disposable biosensor was fabricated by spin-coating technique using star-shaped Star(PGMA) with epoxy side groups. After formation of a stable film with epoxy ends, anti-p53 antibodies were bound to these groups covalently. Stepwise modification of the electrode was followed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) studies. The electrochemical performance of the immunosensor was studied by EIS. Furthermore, the antibody and antigen coupling was monitored by single frequency impedance (SFI) technique. The immunosensor showed a low limit of detection (7 fg/mL) and a linear detection range between 0.02 pg/mL and 4 pg/mL. Additionally, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were utilized for monitoring of immunosensor surface at different stages of fabrication. The antibody coupling on the electrode surface was proved by Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. Furthermore, the proposed immunosensor had good reproducibility and repeatability.
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    A high sensitive and cost-effective disposable biosensor for adiponectin determination in real human serum samples
    (Elsevier, 2021) İnce, Bahar; Sezgintürk, Mustafa Kemal
    One of the adipose tissue cytokines, adiponectin is a newly defined adipocytokin, which is involved in insulin, glucose and adipocyte metabolisms. It has been determined that the amount of adiponectin in the circulatory system decreases in obese and type 2 diabetic patients. In addition to this decrease, many diseases such as heart diseases, high blood pressure, diabetes, joint diseases, high cholesterol, respiratory disease, gallbladder diseases are associated with obesity. Early detection of a decrease in the level of Adiponectin with a biosensor may be a new target for the prevention and treatment of cardiovascular diseases, immune disorder, joint disorders, especially obesity-related pathologies. In the scope of this study, poly ethylene terephthalate (PET) sheets covered with indium tin oxide (ITO), a unique transparent conductive material, was used as a working electrode which, introduced an extremely cheap and flexible material for this purpose. 3-Glycidoxypropyltrimethoxysilane (3-GOPS), an effective organosilane agent, produced a stable layer to immobilize anti-Adiponectin onto the working electrode surface. The immobilization of anti-Adiponectin onto ITO sheets were proved by the tech- niques, Fourier-transform infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). The immunosensor prepared under optimal conditions gave a response in a wide range of concentrations (25 pg/mL–2500 pg/mL with a LOD value of 148 pg/mL) of Adiponectin. Finally, the designed biosensor was applied to real human serum samples and successful results were obtained.
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    A High Sensitive, Reproducible and Disposable Immunosensor for Analysis of SOX2
    (Wiley-V C H Verlag Gmbh, 2020) Tarimeri, Nur; Sezgintürk, Mustafa Kemal
    In this study, an ITO (indium tin oxide) based biosensor was constructed to detect SOX2. SOX2 helps the regulation of cell pluripotency and is closely related to early embryonic development, neural and sexual differentiation. SOX2 is amplified and overexpressed in some malignant tumors such as squamous cell, lung, prostate, breast, esophageal cell, colon, ovarian, glioblastoma, pancreatic cancer, gastric cancer, head and neck squamous cell carcinoma. To generate a hydroxylated clean electrode surface, ITO electrodes were treated with NH4OH/H2O2/H2O. Later, ITO-PET electrode surfaces were modified with 3-glycidoxypropyl trimethoxysilane (3-GOPS). Then, Anti-SOX2 was covalently immobilized onto the electrode surfaces. 3-GOPS concentration, Anti-SOX2 concentration and incubation time, SOX2 incubation time were optimized. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were utilized in order to follow up the immobilization processes and the optimization steps of the biosensor. To characterize the analytical properties of constructed immunosensor; linear range, repeatability, reproducibility and regeneration studies were investigated. The linear range of the immunosensor was detected as 0.625 pg/mL-62.5 pg/mL. Square wave voltammetry technique was also applied to the biosensor. Storage life of the biosensor was determined for identifying the possible usability of the biosensor in clinical field. Finally, the designed biosensor was applied to the real human serum samples. The results obtained with the presented biosensor were also compared with ELISA results.
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    A highly selective electrochemical immunosensor based on conductive carbon black and star PGMA polymer composite material for IL-8 biomarker detection in human serum and saliva
    (Elsevier Advanced Technology, 2018) Aydin, Muhammet; Aydin, Elif Burcu; Sezgintürk, Mustafa Kemal
    A new approach to enhance the electrochemical performance of biosensor was attempted by using Super P (c) carbon black/Star polymer composite material. In this study, we developed an electrochemical IL 8 biosensor by modification with a conductive composite including Super P, polyvinylidene fluoride (PVDF) and star polymer (SPGMA) of disposable ITO electrode surface. The Super P carbon black as carbonaceous material had a high conductivity and was used for the enhancement of electron transfer between electrode surface and electrolyte. Anti-IL 8 antibodies were utilized as biorecognition molecules and bound to epoxy groups of star polymer covalently. The chemical characterization of antibody immobilization on this composite was performed by using Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. The characterizations of stepwise modification of this immunosensor were performed by electrochemical techniques such as Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV) and Single Frequency Impedance (SFI); and morphological techniques such as Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Several variables that affect the immunosensor performance were optimized. Under optimum conditions, a wide linear range 0.01-3 pg/mL and low detection limit 3.3 fg/mL were obtained. Super P-star polymer composite modified immunosensor was easy, sensitive, cheap and reliable analytical method for IL 8 detection. The applicability of the proposed immunosensor to determine IL 8 in saliva and serum samples were examined. The results of biosensor and Enzyme-linked Immunosorbent Assay (ELISA) kit were in compatible. Consequently, it was concluded that the electrochemical immunosensor offers a potential approach for IL 8 detection in clinical applications.
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    A Highly Selective Poly(thiophene)-graft-Poly(methacrylamide) Polymer Modified ITO Electrode for Neuron Specific Enolase Detection in Human Serum
    (Wiley-V C H Verlag Gmbh, 2019) Aydin, Muhammet; Aydin, Elif Burcu; Sezgintürk, Mustafa Kemal
    In this study, an impedimetric immunosensor based on polymer poly(thiophene)-graft-poly(methacrylamide) polymer (P(Thi-g-MAm)) modified indium tin oxide (ITO) electrode is developed for the detection of the Neuron Specific Enolase (NSE) cancer biomarker. First, the P(Thi-g-MAm) polymer is synthesized and coated on the ITO electrode by using a spin-coating technique. P(Thi-g-MAm) polymer acts as an immobilization platform for immobilization of NSE-specific monoclonal antibodies. Anti-NSE antibodies are utilized as biosensing molecules and they bind to the amino groups of P(Thi-g-Mam) polymer via glutaraldehyde cross-linking. Spin-coating technique is employed for bioelectrode fabrication and this technique provides a thin and uniform film on the ITO electrode surface. This bioelectrode fabrication technique is simple and it generates a suitable platform for large-scale loadings of anti-NSE antibodies. This immunosensor exhibits a wide linear detection range from 0.02 to 4 pg mL(-1) and with an ultralow detection limit of 6.1 fg mL(-1). It reveals a good long-term stability (after 8 weeks, 78% of its initial activity), an excellent reproducibility (1.29% of relative standard deviation (RSD)), a good repeatability (5.55% of RSD), and a high selectivity. In addition, the developed immunosensor is proposed as a robust diagnostic tool for the clinical detection of NSE and other cancer biomarkers.
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    A highly sensitive immunosensor based on ITO thin films covered by a new semi-conductive conjugated polymer for the determination of TNF? in human saliva and serum samples
    (Elsevier Advanced Technology, 2017) Aydin, Elif Burcu; Aydin, Muhammet; Sezgintürk, Mustafa Kemal
    A novel, ultrasensitive impedimetric immunosensor was constructed for the detection of tumor necrosis factor alpha (TNF alpha) by using Poly(3-thiophene acetic acid) (P3), a conjugated polymer as an immobilization matrix. The polymer P3 contains a lot of carboxylic acid groups on its surface that provide a larger biorecognition surface. This developed immunosensor was prepared on hydroxy-bearing ITO surface via an ester bond linkage of polymer P3 to immobilize anti-TNF alpha antibodies. The ITO electrode modification steps and interaction between anti-TNF alpha antibody and TNF alpha antigen were monitored by cyclic voltammetry (CV) and by electrochemical impedance spectroscopy (EIS) method. After the analytical parameters optimization, a linear detection response from 0.01 pg/mL to 2 pg/mL, a limit of detection LOD of 3.7 fg/mL and a limit of quantification (LOQ) of 12.4 fg/mL were achieved, which provided accurate results (relative standard deviation; 4.03%). The characterization of this developed immunosensor was performed by using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), SEM-energy dispersive X-ray (EDX) mapping and atomic force microscopy (AFM). The immunosensor allowed a simple and fast detection of TNF alpha antigen in human serum and satisfied recoveries (98.69-105.20%) were obtained by using standard addition method.
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    A label-free dual immunosensor for the simultaneous electrochemical determination of CA125 and HE4 biomarkers for the early diagnosis of ovarian cancer
    (Springer Science and Business Media Deutschland GmbH, 2023) Bilgi Kamaç, Melike; Altun, Muhammed; Yılmaz, Merve; Sezgintürk, Mustafa Kemal
    The blood levels of cancer antigen 125 (CA125) and human epididymal secretory protein 4 (HE4) are measured in the diagnosis and progression monitoring of ovarian cancer (OC), and the Risk of Ovarian Malignancy Algorithm (ROMA) score% values are calculated for cancer risk assessment. For the first time, disposable dual screen-printed carbon electrodes modified with reduced graphene oxide, polythionine, and gold nanoparticles were used to fabricate label-free electrochemical dual CA125-HE4 immunosensors for the sensitive, fast, and practical simultaneous determination of CA125 and HE4. DPV and SWV methods were used to simultaneously determine antigens in two different linear ranges (1–100 pg mL−1 and 1–50 ng mL−1). High sensitivity, low LOD, and LOQ were obtained for two linear ranges with a correlation coefficient above 0.99. The application stability of the dual CA125-HE4 immunosensors was determined as 60 days, and the storage stability was determined as 16 weeks. The dual immunosensors exhibited high selectivity in eight different antigen mixtures. The reusability of the dual immunosensors has been tested up to 9 cycles. ROMA score% values for pre-menopausal and post-menopausal status were calculated using the concentration of CA125 and HE4 in the blood serum and assessing OC risk. The disposable dual immunosensors can be used in point-of-care tests for rapid and practical simultaneous determination of CA125 and HE4 with high selectivity, sensitivity, and repeatability.
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    A label-free electrochemical biosensor for direct detection of RACK 1 by using disposable, low-cost and reproducible ITO based electrode
    (Elsevier Science Bv, 2018) Torer, Hakan; Aydin, Elif Burcu; Sezgintürk, Mustafa Kemal
    In this study we designed an ultrasensitive electrochemical immunosensor for RACK 1 detection using 11-cyanoundecyltrimethoxysilane (11-CUTMS) as a immobilization matrix to immobilize biorecognition element. The used silane agent (11-CUTMS) provides a favorable platform for efficient loading of anti-RACK 1 antibody. The effective loading of the biorecognition element on the 11-CUTMS matrix was monitored by scanning electron microscopy (SEM), atomic force microscopy (AFM) images and fourier transform infrared spectroscopy (FTIR) spectra. The electrochemical characterization of the immunosensor was performed by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Moreover, biorecognition interaction between anti-RACK1 antibodies and RACK1 antigens was monitored by using single frequency technique (SFI). The operating conditions, calibration curves obtained during optimization of experiments and reproducibility of the proposed impedimetric RACK1 biosensor are also investigated and discussed. The electrochemical immunosensor illustrated a sensitive response to RACK 1 antigen with detection limit of 10.8 fg/mL and in the linear range of 0.036 -2.278 pg/mL (R-2 = 0.999). Owing to high specificity, good reproducibility, long stability and reusability, the fabricated immunosensor will provide a sensitive, selective approach to RACK 1 detection. Furthermore, the practical applicability in human serum samples were investigated with a satisfactory result. (C) 2018 Elsevier B.V. All rights reserved.
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    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) Aydın, Elif Burcu; Aydın, Muhammet; Sezgintürk, Mustafa Kemal
    In 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.
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    A Label-free Electrochemical Immunosensor for Highly Sensitive Detection of TNF alpha, Based on Star Polymer-modified disposable ITO Electrode
    (Bentham Science Publishers, 2021) Aydın, Elif Burcu; Aydın, Muhammet; Sezgintürk, Mustafa Kemal
    Background: Biomarkers are very important disease-related biomolecules which should be analyzed sensitive and selective in related physiological fluids or tissues. Tumor necrosis factor-α is a type of cytokine which plays vitlly important roles in different methabolic pathways such as cell death, survival, differentiation, proliferation and migration, and infectious and inflammatory diseases including rheumatoid arthritis, diabetes. Objective: In this study, it was aimed to develop a reliable tool based on star-shaped poly(glycidyl methacrylate) polymer coated disposable indium tin oxide electrode for determination of Tumor necrosis factor-α, an important disease biomarker. Methods: Star shaped polymer was used as an interface material for anti-Tumor necrosis factor α antibodies immobilization. The antibodies were immobilized covalently onto polymer coated indium tin oxide electrode. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were used for all electrochemical measurements. Results: The suggested immunosensor exhibited a linear range between 0.02 and 4 pg/mL Tumor necrosis factor-α, and the detection limit was found as 6 fg/mL. Scanning electron microscopy and atomic force microscopy were used for electrode surface characterization. In addition, the suggested im-munosensor was used for Tumor necrosis factor-α sensing in human serum samples. The results dis-played recoveries between 97.07 and 100.19%. Moreover, this immunosensor had a simple fabrication procedure and a long storage-stability. Conclusion: A new biosensor based on a Star shaped polymer for the ultra sensitive determination of a biomarker Tumor necrosis factor-α was developed. The biosensor presented excellent repeatability and reproducubility, and also wide calibration range for Tumor necrosis factor-α.
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    A label-free immunosensor for sensitive detection of RACK 1 cancer biomarker based on conjugated polymer modified ITO electrode
    (Elsevier, 2020) Aydin, Elif Burcu; Aydin, Muhammet; Sezgintürk, Mustafa Kemal
    A new flexible biosensor based on conjugated polymer functionalized indium tin oxide (ITO) sheet was fabricated for Receptor for Activated C Kinase 1 (RACK 1) determination. Poly(3-thiophene acetic acid) (P(Thi-Ac)) was used as an immobilization matrix for construction of RACK 1 immunosensor. This polymer had a great number of carboxyl groups on its end site and these carboxyl ends provided anchoring points to the anti-RACK 1 antibodies. Anti-RACK 1 antibodies were covalently attached on the ITO electrode and recognized the RACK 1 antigens. Electrochemical characterizations were made by employing electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Additionally, single frequency impedance method (SFI) was applied to follow the specific biointeraction between antibody and antigen. As a result of specific biointeraction, the designed immunosensor exhibited a wide linear detection range between 0.01 pg/mL and 2 pg/mL RACK 1 with a detection limit of 3.1 fg/mL. Scanning electron microscopy and atomic force microscopy analyses were employed for electrode surface morphology investigation. The designed RACK 1 biosensor had good repeatability (5.73 %, RSD), excellent reproducibility (2.5 %, RSD), long storage-stability and reusable property. In addition, the fabricated RACK 1 biosensor was applied to determine RACK 1 concentration in human serums and the recovery was ranging from 98.79%-100.22%. This work illustrated a new tool to construct a sensitive and low-cost disposable biosensor for applications in clinical monitoring. (C) 2020 Elsevier B.V. All rights reserved.
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    A nano-composite based regenerative neuro biosensor sensitive to Parkinsonism-associated protein DJ-1/Park7 in cerebrospinal fluid and saliva
    (Elsevier B.V., 2021) Sonuç Karaboğa, Münteha Nur; Sezgintürk, Mustafa Kemal
    In this study, we developed an electrochemical-based single-use neurobiosensor based on multiwalled carbon nanotube (MWCNT)-gold nanoparticle (AuNP) nanocomposite doped, 11-amino-1-undecanethiol (11-AUT)-modified polyethylene terephthalate coated indium tin oxide (ITO-PET) electrodes. This electrode was used for the sensitive determination of DJ-1, a protein responsible for mitochondrial dysfunction in Parkinson's disease (PD) with the task of eliminating oxidative stress. The design strategy and analytical studies for the neurobiosensor were monitored with electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and single frequency impedance (SFI) techniques. The selective determination range for DJ-1 of the developed neurobiosensor system is 4.7–4700 fg mL−1 in accordance with the charge transfer resistance (Rct) associated with a limit of detection of 0.5 fg mL−1. Since changes in the expression of DJ-1 protein is particularly important in cerebrospinal fluid (CSF) and saliva, the ability of the developed neurobiosensor system to detect the DJ-1 protein in these media was tested by the standard addition method. The statistical results show that the biosensor decorated with MWCNT-AuNP-AUT may be recommended for the selective determination of DJ-1 protein.
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    A New Approach to Synthesis of Highly Dispersed Gold Nanoparticles via Glucose Oxidase-Immobilized Hydrogel and Usage in The Reduction of 4-Nitrophenol
    (Wiley-V C H Verlag Gmbh, 2020) Ozay, Hava; Tarimeri, Nur; Gungor, Zeynep; Demirbakan, Burcak; Ozcan, Burcu; Sezgintürk, Mustafa Kemal; Özay, Özgür
    In this study, for the first time in the literature, synthesis of Au(0) nanoparticles supported by a crosslinked gel structure was performed via enzyme-mediated reduction of Au(III) ions without using any chemical reductant. In our newly-developed method, glucose oxidase enzymes immobilized in the crosslinked gelatine structure ensured simultaneous reduction of the Au(III) ions diffused within the gel to Au(0). The Au@Gel obtained was structurally characterised with TEM (Transmission electron microscopy), EDX (Energy dispersive X-ray analysis) elemental mapping, XPS (X-Ray photoelectron spectroscopy) and XRD (X-Ray Diffraction) analyses. The catalytic activity of Au(0) particles with nearly 8 nm size in the Au@Gel was investigated for the reduction of 4-nitrophenol (4-NP) as a model compound in the presence of NaBH(4)as reducing agent. The activation parameters for the reduction reaction of 4-nitrophenol in the presence of Au@Gel catalyst were determined as E-a= 30.16 kJmol(-), Delta H= 27.52 kJmol(-)and Delta S= -197.45 Jmol(-)K(-). The Au@Gel catalyst system, with good catalytic activity, simultaneously has nearly perfect reusability.
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    A new immunosensing platform based on conjugated Poly(ThidEp-co-EDOT) copolymer for resistin detection, a new obesity biomarker
    (Springer, 2024) Aydın, Elif Burcu; Aydın, Muhammet; Sezgintürk, Mustafa Kemal
    The 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.
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    A novel and disposable GP- based impedimetric biosensor using electropolymerization process with PGA for highly sensitive determination of leptin: Early diagnosis of childhood obesity
    (Elsevier, 2021) Özcan, Burcu; Sezgintürk, Mustafa Kemal
    This study presents a novel, single-use electrochemical biosensor for the leptin biomarker, which may have potential use for early diagnosis of childhood obesity. The graphite paper working electrode was used for the first time in impedimetric biosensors. All immobilization procedure, investigation of the optimal parameters and characterization of biosensors were followed and evaluated using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). The Scanning Electron Microscope (SEM) was utilized to visualize the morphology of the electrode surface during the immobilization steps of the immunosensor. Moreover, the characterization of the interactions between anti-leptin and leptin was investigated by using Single Frequency Technique (SFI). The applicability of the designed biosensor for real serum samples was tested for clinical use. It was observed that the biosensor allows high sensitivity in the analyte detection (leptin) in real serum samples. Moreover, it was suggested that the developed biosensor presents advantages such as long shelf life (5% loss of activity after 8 weeks and 60% loss after 10 weeks), ability to determine analyte concentrations at picogram level (0.2 pg mL−1 -20 pg mL−1), low limit of detection (0.00813 pg mL− 1), reproducibility, reusability (12 times) and high sensitivity.