Dopamin is neurotransmitter, which play significant role in the functioning of central nervous, renal and hormonal systems. Dopamine is also illegally used in the doping. Its concentration varied from 0,163 nM in the blood to 384-2360 nM in urine. The concentration of dopamine in the extracellular fluid of central nervous system is 0,01-1 µM. Development of sensitive method of detection dopamine is urgently needed for diagnosis and also in the purpose of anti-doping tests. Currently the detection of dopamine is based on electrochemical methods, HPLC, fluorimetry and capillary electroforesis.

Our approach is based on the detection of the dopamine by the quartz crystal microbalance (QCM) using thickness shear mode method (TSM). As a receptor we used 25.26.27.28-tetrakis(11-sulfanylundecyloxy) calix[4]arene (calix[4]arene) that has been chemisorbed on a gold surface of quartz crystal resonator. We studied the kinetics of the changes of the series resonant frequency, f_s, and the motional resistance, R_m, of the quartz crystal transducer following addition of dopamine. We observed typically the decrease of f_s and increase of R_m, following addition of dopamine. The increase of R_m suggests on increase of surface viscosity. The changes of both parameters started already at 53 pM of dopamine. The topography of the layers was investigated by atomic force microscopy in taping magnetic mode. The images of the calix[4]arene layers in an air environment revealed smooth surface with irregular pinholes.

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