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    Electrochemical detection of cortisol by silver nanoparticle-modified molecularly ımprinted polymer-coated pencil graphite electrodes
    (Amer Chemical Soc, 2023) Shama, Nemah Abu; Asır, Süleyman; Göktürk, Ilgım; Yılmaz, Fatma; Türkmen, Deniz; Denizli, Adil
    The sensitive cortisoldetection by an electrochemicalsensor basedon silver nanoparticle-doped molecularly imprinted polymer was successfullyimproved. This study describes the method development for cortisoldetection in both aqueous solution and biological samples using molecularlyimprinted poly(hydroxyethyl methacrylate-N-methacryloyl-(l)-histidine methyl ester)-coated pencil graphite electrodesmodified with silver nanoparticles (AgNPs) by differential pulse voltammetry(DPV). The cortisol-imprinted pencil graphite electrode (PGE) hasa large surface area because of doped AgNPs with enhanced electroactivity.The prepared molecularly imprinted polymer was characterized by scanningelectron microscopy. The DPV response of the synthesized electrodewith outstanding electrical conductivity was clarified. Cortisol-imprintedpolymer-coated PGEs (MIP), cortisol-imprinted polymer-coated PGEswith AgNPs (MIP@AgNPs), and nonimprinted polymer-coated PGEs withAgNPs (NIP@AgNPs) were evaluated for sensitive and selective detectionof cortisol in aqueous solution. Five different cortisol concentrations(0.395, 0.791, 1.32, 2.64, and 3.96 nM) were applied to the MIP@AgNPs,and signal responses were detected by the DPV with a regression coefficient(R (2)) value of 0.9951. The modified electrodeshowed good electrocatalytic activity toward cortisol for the linearconcentration range from 0.395 to 3.96 nM, and a low limit of detectionwas recorded as 0.214 nM. The results indicate that the MIP@AgNPssensor has great potential for sensitive and selective cortisol determinationin biological samples.
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    Gold-modified molecularly imprinted N-methacryloyl-(l)-phenylalanine-containing electrodes for electrochemical detection of dopamine
    (MDPI, 2022) Shama, Nemah Abu; Aşır, Süleyman; Özsöz, Mehmet; Göktürk, Ilgım; Türkmen, Deniz; Yılmaz, Fatma; Denizli, Adil
    A molecularly imprinted polymer-based pencil graphite electrode (MIP PGE) sensor, modified with gold nanoparticles, was utilized for the detection of dopamine in the presence of other biochemical compounds using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), depending on its strong electroactivity function. The pulse voltammetry methods recorded the highest response. In addition to the high oxidation rate of DA and the other biomolecule interferences available in the sample matrix used, which cause overlapping voltammograms, we aimed to differentiate them in a highly sensitive limit of detection range. The calibration curves for DA were obtained using the CV and DPV over the concentration range of 0.395-3.96 nM in 0.1 M phosphate buffer solution (PBS) at pH 7.4 with a correlation coefficient of 0.996 and a detection limit of 0.193 nM. The electrochemical technique was employed to detect DA molecules quantitatively in human blood plasma selected as real samples without applying any pre-treatment processes. MIP electrodes proved their ability to detect DA with high selectivity, even with epinephrine and norepinephrine competitor molecules and interferences, such as ascorbic acid (AA). The high level of recognition achieved by molecularly imprinted polymers (MIPs) is essential for many biological and pharmaceutical studies.