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    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.
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    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, Selahattin
    The 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.