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Öğe A novel and mass-sensitive quartz tuning fork platform for glial fibrillary acidic protein determination(Elsevier, 2025) Özcan, Burcu; Uludağ, İnci; Ünal, Mehmet Altay; Arı, Fikret; Sezgintürk, Mustafa Kemal; Özkan, Sibel A.Traumatic brain injury (TBI) is a major cause of mortality and disability worldwide, and its diagnosis is still difficult. A unique blood biomarker for numerous neurological disorders, including traumatic brain injury, is glial fibrillary acidic protein (GFAP). Portable, quick, and functional equipments are crucial in fighting against neurological illnesses. Quartz Tuning Fork (QTF) biosensors are attracting great attention due to their seamless integration with miniaturized and portable devices. This study introduces a new, adaptable, affordable frequency analyzer for GFAP detection. A simple and stable process to design a QTF system which has gold surface modified with 3-mercaptopropionic acid (3-MPA) and its biocompatibility with GFAP antigen was investigated. The surface morphology of the QTF system was analyzed during its immobilization procedure using Atomic Force Microscopy (AFM). The constructed QTF sensor system demonstrated high repeatability (the standard deviation: +/- 0.12183 Hz), good reproducibility, linearity, ability to detect antigen concentrations at femtogram levels. It proved that the QTF sensor system decorated with 3-MPA could be a good choice for the sensitive determination of GFAP, according to the statistical data. The modified QTF sensor demonstrated remarkably straightforward and mass-sensitive GFAP detection. The developed QTF-based biosensor achieved an outstanding linear detection range of 1-100 fg mL-1. The responses of the designed QTF-based sensor to commercial human serum also show that it is a successful and promising system for clinical use.Öğe A novel electrochemical approach to biosensing applications: Quartz tuning forks as working electrodes for immunosensors(Elsevier, 2023) Arı, Fikret; İnce, Bahar; Ünal, Mehmet Altay; Sezgintürk, Mustafa Kemal; Özkan, 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 Electrochemical behavior of formoterol fumarate and its determination in capsules for inhalation and human serum using differential-pulse and square-wave voltammetry(Wiley-V C H Verlag Gmbh, 2002) Demircigil, B. T.; Özkan, Sibel A.; Çoruh, Ö.; Yılmaz, SelahattinThe electrochemical oxidation of formoterol fumarate (formoterol) has been carried out in aqueous solution in the pH range of 1.5-10.0 by cyclic, linear sweep, differential-pulse and square-wave voltammetry. The diffusion controlled nature of the waves was established. The mechanism of oxidation was discussed, Two voltammetric techniques for the determination of formoterol in 0.5 M sulfuric acid which allow quantitation over the 8 x 10 (6)-6 X 10 (-5) M range for both methods were proposed. Based on this study simple, rapid and selective two voltammetric methods were developed for the determination of formoterol in capsule dosage form and human serum.Öğe Quartz tuning fork biosensor: A potential tool for SARS-CoV-2 detection(Elsevier, 2023) Kavacık, Mehmet; İnce, Bahar; Arı, Fikret; Ünal, Mehmet Altay; Sezgintürk, Mustafa Kemal; Özkan, 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.
