Browsing by Author "Subak, Hasret"

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Development and Applications of Electrochemical Dna Biosensors for the Study of Selective Estrogen Receptor Modulators (serm) Raloxifene
(2024) Mustafa, Saboor Yousıf Mustafa; Subak, Hasret
Selektif Östrojen Reseptörü Modülatörü (Serm) Raloksifenin İncelenmesi İçin Elektrokimyasal Dna Biyosensörlerin Geliştirilmesi Ve Uygulamaları, Raloksifen (Ralo) ([6-hidroksi-2-(4-hidroksifenil)-1- benzotiyofen-3-il]-[4-(2-piperidin-1-iletoksi)fenil]metanon), seçici bir östrojen reseptör modülatörüdür (SERM) kanser tedavisinde kullanılmaktadır. Östrojen reseptörlerinin iki farklı yapısı vardır: alfa ve beta. SERM maddeleri bu reseptörlere bağlanarak antagonist ve agonist etkilere sahiptir. SERM'ler, 3 boyutlu konformasyonu kullanarak bazı dokularda östrojen agonisti ve antagonisti etkilerine neden olan nonsteroidal bileşiklerdir. En iyi bilinen SERM'ler Ralo ve tamoksifendir (TAM). TAM östrojen reseptörlerini etkileyerek vücutta tedavi edici ve yan etki yaratan mekanizmalara neden olur. Tam, göğüs hücrelerinde östrojen antagonisti olarak görev yapar, ancak rahimde östrojen agonisti olarak hareket ederek endometriyumu uyarır. Öte yandan RALO, göğüs hücresi östrojen reseptörlerini antagonist olarak etkiler ve rahmi uyarmaz. Bu tez, tek kullanımlık elektrokimyasal biyosensör kullanılarak Ralo ve DNA arasındaki etkileşimi araştırdı. İlk olarak Ralo'nun elektrokimyasal davranışı, 2,0-12,0 pH aralığında sulu çözeltilerde döngüsel ve kare dalga voltametri ile incelenmiştir. Ralo'nun tespit limiti 5,63 µM (2.66 µg/mL) olarak hesaplandı (doğrusallık aralığı 1,25 ile 50 µg/mL arası). Ayrıca Ralo ve DNA dizileri arasındaki etkileşimi sağlamak için kalem grafit elektrot (PGE) kullanılarak elektrokimyasal bir biyosensör tasarlandı. Sonuç olarak geliştirilen biyosensör, Ralo-DNA etkileşiminin hassas bir şekilde analiz edilmesi için uygun bir aşama sağlamaktadır. Bu çalışmada antikanser ilacının DNA ile modifiye edilmiş elektrotlarla etkileşimi araştırıldı. Antikanser ilacı Ralo'nun DNA'ya bağlanma mekanizması elektrokimyasal voltametri yöntemleri kullanılarak belirlendi. Bu amaçla DNA ile modifiye edilmiş elektrotlar hazırlandı ve Ralo ile etkileşime sokulduktan sonra elektrokimyasal analizle ölçüldü. Özetle, tek kullanımlık elektrokimyasal biyosensörler kullanılarak Ralo-DNA etkileşiminin etiketsiz tespitinin hassas, daha hızlı ve daha az zahmetli tekniklerle yapılabileceği gösterilmiştir.
Electrochemical Behavior of Janus Kinase Inhibitor Ruxolitinib at a Taurine-Electropolymerized Carbon Paste Electrode: Insights Into Sensing Mechanisms
(Amer Chemical Soc, 2024) Subak, Hasret; Pinar, Pinar Talay
Ruxolitinib (RXL) is a Janus kinase inhibitor used for treating intermediate- or high-risk myelofibrosis. This study presents an electrode modified with electrochemically polymerized taurine on a carbon paste electrode via cyclic voltammetry (CV). The surface characterization of the poly(taurine)-CP electrode was evaluated by using electrochemical (electrochemical impedance spectroscopy-EIS, CV), morphological (scanning electron microscope-SEM), and spectroscopic (Fourier-transform infrared spectroscopy-FT-IR) techniques. Under optimized conditions, RXL exhibited good linearity within the 0.01-1.0 mu M concentration range, with a limit of detection (LOD) of 0.005 mu M. The proposed electrochemical sensor demonstrated excellent selectivity, accuracy, precision, and repeatability. Furthermore, it effectively detected RXL in human urine and pharmaceutical samples.
Electrochemical Biosensing: From Interaction Between Epilobium Species and Dna To an Approach To Detect New Electroactive Components in Plant Extracts and Their Effects on Dna
(Springer Heidelberg, 2024) Subak, Hasret; Dalar, Abdullah; Mukemre, Muzaffer; Ozkan-Ariksoysal, Dilsat
Here, a simple and label-free biosensor based on disposable pencil graphite electrode (PGE) was developed for the first time to investigate the interaction between Epilobium sp. plant extract containing active compounds (quercetin and kaempferol) and DNA using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The solution of extract was interacted with calf thymus double-stranded DNA (dsDNA) which immobilized onto the biosensor surface by simple adsorption. The effect of Epilobium on double-stranded DNA (dsDNA) was then analyzed by monitoring the changes in electrochemical signals arising from both guanine bases in DNA and the electroactive compounds in Epilobium extract. Epilobium content was also detected by using HPLC/MS/MS technique, and the gained results were compared with those obtained by electrochemical method. It was found that both methodologies supported each other in terms of active ingredients in Epilobium sp. Numerous factors affecting the extract-DNA interaction were optimized such as Epilobium concentration, interaction time. The developed DNA sensor can well detect Epilobium extract-DNA interaction in 60-min detection time with 26 ng of detection limit in 50 mu L of sample volume with a linear range from 1 to 10 mu g/mL. This study includes alternative method that can be used to detect new electroactive components present or to be found in different plant extracts and their interactions with DNA.
Electrochemical Biosensor for Simultaneously Detection of Tamoxifen
(2022) Subak, Hasret
Cancer is described as the uncontrollably multiplying abnormal proliferation of cells. Cancer can affect everyone, and risk of which rises with age, lifestyle, and environmental toxins. Tamoxi̇fen (TAM) which is a selective estrogen receptor modulator, has estrogenic or antiestrogenic effects on the breast tissue by binding to the estrogen receptors. The current study presents a voltammetric biosensor to identify the effect of Tamoxifen on DNA structure. In this study, the effect of TAM on the double-stranded DNA (dsDNA) was investigated electrochemically in both the presence and absence of antioxidants. For this purpose, TAM-dsDNA-antioxidant interaction investigated by using the pencil graphite electrode (PGE). The DNA modified sensor was created simply by wet-adsorbtion method. The prepared biosensor was examined electrochemically by square wave voltammety (SWV) method, and its lowest concentration and optimum pH range were determined. The effect of TAM on dsDNA was investigated simultaneously for the first time in the literature.
Electrochemical Oxidation of Ranitidine Using a Boron-Doped Diamond Electrode in the Presence of Anionic Surfactant: a Comprehensive Investigation
(2024) Subak, Hasret; Pınar, Pınar Talay
Ranitidine (RAN) is a drug from the histamine H2 receptor antagonist class and is used to prevent excessive production of stomach acid. An electrochemical investigation of the RAN in pharmaceutical preparation and spiked human urine was performed for the using a boron-doped diamond electrode (BDDE). Voltammetric measurements were performed in a pH 11 BR solution supplemented with the anionic surfactant, sodium dodecyl sulfate (SDS). In the proposed method using optimized experimental conditions, linearity was obtained for RAN in the concentration range of 0.8-50.0 μM. The LOD value obtained is 0.22 μM. Good selectivity, accuracy, precision, and acceptable repeatability were also achieved in this proposed electrochemical sensor. Finally, this electrochemical sensor was successfully used for RAN detection in pharmaceutical samples.
Label-Free Electrochemical Biosensor for the Detection of Influenza Genes and the Solution of Guanine-Based Displaying Problem of Dna Hybridization
(Elsevier Science Sa, 2018) Subak, Hasret; Ozkan-Ariksoysal, Dilsat
The differentiation of fully matched and unlabelled Influenza A (Inf A) or B (Inf B) target DNA obtained from polymerase chain reaction (PCR)-amplified real samples towards non-complementary sequences have been analyzed with an extremely simple electrochemical methodology by developed label-free electrochemical DNA biosensor without any surface modification. In the meanwhile, this is the first study that contains the solution of the guanine signal-based displaying problem of DNA hybridization which has been solved by designed biosensor. The monitoring of guanine oxidation signal affected by experimental conditions and the response showed significant differences depending on the nature and composition of DNA. In the presented work, the effect of differences in the number of inosine in probe DNA on hybridization imaging was also discussed. The electrochemical oxidation of guanine (approximately +1.00V) was measured at pencil graphite electrode (PGE) by using differential pulse voltammetry (DPV) technique and evaluated before and after hybridization between probe and target DNAs. Several hybridization solutions and rinsing protocols with different ionic strengths have been utilized to achieve optimum hybridization displaying response. The selectivity of developed genosensor was also tested at the same time with hybridization. The detection limits of sensors were calculated as 35 nM for Inf A and 21 nM for Inf B sequences. (C) 2018 Elsevier B.V. All rights reserved.
Mycotoxins Aptasensing: From Molecular Docking To Electrochemical Detection of Deoxynivalenol
(Elsevier Science Sa, 2021) Subak, Hasret; Selvolini, Giulia; Macchiagodena, Marina; Ozkan-Ariksoysal, Dilsat; Pagliai, Marco; Procacci, Piero; Marrazza, Giovanna
This work proposes a voltammetric aptasensor to detect deoxynivalenol (DON) mycotoxin. The development steps of the aptasensor were partnered for the first time to a computational study to gain insights onto the molecular mechanisms involved into the interaction between a thiol-tethered DNA aptamer (80mer-SH) and DON. The exploited docking study allowed to find the binding region of the oligonucleotide sequence and to determine DON preferred orientation. A biotinylated oligonucleotide sequence (20mer-BIO) complementary to the aptamer was chosen to carry out a competitive format. Graphite screen-printed electrodes (GSPEs) were electrochemically modified with polyaniline and gold nanoparticles (AuNPs@PANI) by means of cyclic voltammetry (CV) and worked as a scaffold for the immobilization of the DNA aptamer. Solutions containing increasing concentrations of DON and a fixed amount of 20mer-BIO were dropped onto the aptasensor surface: the resulting hybrids were labeled with an alkaline phosphatase (ALP) conjugate to hydrolyze 1-naphthyl phosphate (1-NPP) substrate into 1-naphthol product, detected by differential pulse voltammetry (DPV). According to its competitive format, the aptasensor response was signal-off in the range 5.0-30.0 ng.mL(-1) DON. A detection limit of 3.2 ng.mL(-1) was achieved within a 1-hour detection time. Preliminary experiments on maize flour samples spiked with DON yielded good recovery values. (C) 2020 Elsevier B.V. All rights reserved.
Nanomolar Detection and Electrochemical Mechanism of Nintedanib Via Square-Wave Voltammetry Using a Mwcnt-Modified Glassy Carbon Electrode
(Elsevier Science Sa, 2025) Subak, Hasret; Bas, Halime; Pinar, Pinar Talay
This study focuses on the electrochemical analysis of Nintedanib (NTD), a therapeutic agent used to treat idiopathic pulmonary fibrosis (IPF), employing a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNT). The electrochemical modified electrode was comprehensively characterized using techniques such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and field emission scanning electron microscopy (FE-SEM). Afterward, the MWCNT-modified GCE was optimized to enhance its performance for detecting NTD. For the first time, an electrochemical oxidation mechanism of NTD was suggested using this sensor. The optimized sensor showed excellent linearity within the concentration range of 0.01 to 0.40 mu M and achieved a detection limit as low as 0.0037 mu M. Moreover, the sensor proved to be effective in analyzing NTD in biological samples. These results underline the strong potential of the MWCNTmodified GCE as a highly sensitive platform for NTD electrochemical analysis.
Novel Determination of the Influence of Idarubicin Upon Dna Chain Structure Using an Electrochemical Dna Biosensor by Voltammetry
(Taylor & Francis inc, 2024) Subak, Hasret
Two sequences of DNA (single-strand DNA (ssDNA) and double-strand DNA (dsDNA)) modified disposable electrodes were designed to investigate the effect of antitumor agent drug idarubicine (IDA) on the DNA chain structure. The effect of IDA on DNA structure was analyzed by square wave voltammetry (SWV) depending on not only the guanine signal but also IDA oxidation response. The present study included the electrochemical investigation of IDA and the investigation of the biomolecular interaction between IDA and DNA. IDA was detected in buffer and urine using disposable pencil graphite electrodes (PGE) with SWV and cyclic voltammetry (CV)). The detection limit (LOD) of IDA in urine samples was 0.089 mu g mL-1 with SWV under optimum conditions. For the biomolecular interaction of IDA and DNA, all electrochemical conditions, such as the concentration of DNA, concentration of IDA, interaction phase (at electrode surface/in solution phase), the interaction pH, and the interaction time were optimized. IDA interacted biomolecularly with DNA at the electrode surface and in solution phase using two methods. There is no previous electrochemical study performed on the interaction of IDA with ssDNA. Hence, the effect of IDA on both ssDNA and dsDNA was presented for the first time.
Ready-To Diagnostic Kit Based on Electrochemical Nanobiosensor for Antibiotic Resistance Gene Determination
(Elsevier, 2024) Subak, Hasret; Yilmaz, Fethiye Ferda; Ozkan-Ariksoysal, Dilsat
Nowadays, antibiotic resistance, which occurs as a result of mutations in bacterial genes due to the frequent use of antibiotics, causes serious health problems and deaths. One of the resistance mechanisms that develop with the use of antibiotics is that bacteria begin to produce carbapenemase enzymes that cause multiple drug resistance in bacteria by hydrolyzing antibiotics. In this study, an alternative diagnostic kit method to traditional tests was developed for the determination of bacteria carrying relevant antibiotic resistance genes because these analyzes have multi-step sample preparation, long/complex determination schemes and are high cost. With the diagnostic kit containing a stable electrochemical nanobiosensor developed in this study, the presence of two different antibiotic resistance gene regions of the carbapenemase enzyme named OXA-48 and VIM, which are responsible for more than 50 % of deaths due to antibiotic resistance, was investigated. Carbon nanotubes (CNTs) has been modified to the pencil graphite electrode (PGE), then the synthetic capture probe DNAs are immobilized covalently to the surface containing nanomaterial. Later, the sensor surface, whose stability was ensured by surface blockage, thus gained "diagnostic kit feature" and was stored in the refrigerator (+4 degrees C) until analysis. Thus, the preparation of a ready-to-analyze diagnostic kit, which will provide detection without any preparation, has been completed. With the developed kit, it was possible to determine the resistance gene with 2.5 pmole/50 mu L of detection limit. In addition, analyzes with real samples could be performed even after 150 days (5 months) of kit preparation. This represents the first diagnostic kit system containing PGE and CNT for the detection of antibiotic resistance based on electrochemical alpha naphthol signal measurement in real samples with symmetrical and asymmetric structures (PCR). In the developed alternative test platform, the sample volume required for determination is 50 mu L and the analysis time with this portable open-use and throw-away diagnostic kit is 30 min.