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Öğe A novel electrochemical approach to biosensing applications: Quartz tuning forks as working electrodes for immunosensors(Elsevier, 2023) Ari, Fikret; Ince, Bahar; Unal, Mehmet Altay; Sezgintürk, Mustafa Kemal; Ozkan, Sibel A.Although cutting-edge technology has improved our understanding of many cancers, the diagnostic and treatment options available still need to be improved. Electrochemical biosensors play a key role as the most suitable platform used for this purpose. Quartz tuning forks (QTF) sensors have recently become the most valuable components for frequency measurements, with high stability, sensitivity, and low power consumption. No paper has previously been reported on the functionalization and isolation of QTF for biomarker determination using electrochemical methods, marking this research as unique for being the first to investigate the response and sensitivity of QTFs in these applications. Cardiac troponin T (cTnT), an important biomarker of cardiovascular disease, a four-step surface modification was performed to the prepared QTFs' prongs. The surface was investigated in detail utilizing cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. The results showed that the QTF-based immunosensor's limit of quantitation (LOQ) was 0.81 fg/mL, and the limit of detection (LOD) was 0.24 fg/mL, with a detection range of 0.5-1500 fg/mL. The results confirmed that QTFs have unique electrode capacity in point-of-care diagnostic devices. Most importantly, due to their excellent sensitivity and low cost, QTF transducers are predicted to be widely used as a unique electrode to detect many biomarkers in EIS and CV-based electrochemical biosensors.Öğe Bioprocess monitoring by biosensor-based technologies(Elsevier, 2020) Goker, Meric; Kurbanoglu, Sevinc; Huri, Pinar Yilgor; Sezgintürk, Mustafa Kemal; Ozkan, Sibel A.Today, biotechnological process applications are frequently used by an increasing importance in terms of industry and research. One of the natural consequences of scientific advances is the provision of more rapid progression by the effects on several scientific fields. Therefore, the rapid introduction of biotechnological processes into our daily lives leads to the development of new experimental tools (imaging methods and metabolic engineering), universal methods of analysis (genomics, proteomics, and metabolomics), and bioinformatics, which are able to respond rapidly to the needs and become more responsive. In this chapter, it is tried to define the bioprocess monitoring and analytical methods for bioprocesses with their measurement principles. Moreover, biologically varying sensors that are used in biomass monitoring and biomass concentration analysis are also defined. Turbidity sensors and impedance sensors, cell morphology analysis, in situ microscope systems, metabolic activity analysis, etc., are also stated. Current challenges with some novel examples are also shared. © 2020 Elsevier Inc. All rights reserved.Öğe Quartz tuning fork biosensor: A potential tool for SARS-CoV-2 detection(Elsevier, 2023) Kavacik, Mehmet; Ince, Bahar; Ari, Fikret; Unal, Mehmet Altay; Sezgintürk, Mustafa Kemal; Ozkan, Sibel A.Portable, fast, and practical devices are important in the fight against epidemic diseases. The lack of readily available small-scale commercial solutions prompted us to delve deeper into this research effort. Investment in Quartz Tuning Fork (QTF)-based biosensor research is significant due to its seamless integration with miniaturised and portable devices. Within the scope of this study, a new, cost-effective, and versatile frequency analyser designed for detecting diseases, compatible with screens of different sizes, has been introduced. The modified QTF sensor occured mass-sensitive SARS-CoV-2 nucleocapsid protein (SARS-NP) detection with remarkable simplicity, sensitivity, and selectivity. The developed QTF-based biosensor has an impressive linear detection range ranging from 5 to 200 ng/mL and an exceptionally low limit of detection (LOD) value of 1.72 ng/ mL. The sensitivity of the developed QTF-based biosensor was obtained as 50 Hz/1 mu M. The biosensor response was then evaluated in commercial human serum sample. After 15 days of storage, these biosensors retained approximately 93.7 % of their initial activity. Additionally, a Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) comprehensively characterised the electrode surface.Öğe Sensitive voltammetric determination of famotidine in human urine and tablet dosage forms using an ultra trace graphite electrode(Serbian Chemical Soc, 2014) Yagmur, Sultan; Yilmaz, Selehattin; Saglikoglu, Gulsen; Uslu, Bengi; Sadikoglu, Murat; Ozkan, Sibel A.In this study, the direct and sensitive determination of famotidine based on its electrochemical oxidation was investigated in spiked human urine and tablet dosage forms. The electrochemical measurements were performed in various buffer solutions in the pH range 0.88-12.08 at an ultra trace graphite electrode (UTGE) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The best results were obtained for the quantitative determination of famotidine by the DPV technique in 0.5 mol L-1 H2SO4 solution (pH 0.30). In this strong acid medium, one irreversible anodic peak was observed. The effects of pH and scan rate on the peak current and peak potential were investigated. The diffusion-controlled nature of the peak was established. For optimum conditions described in the experimental section, a linear calibration curve for DPV analysis was constructed in the famotidine concentration range 2x10(-6)-9x10(-5) mol L-1. The limit of detection (LOD) and limit of quantification (LOQ) were 3.73x10(-7) and 1.24x10(-6) mol L-1 at a UTGE, respectively. The repeatability, precision and accuracy of the developed technique were checked by recovery studies in spiked urine and tablet dosage forms.
