High sensitive calixarene-based sensor for detection of dopamine by electrochemical and acoustic methods.

We synthesized 25,26,27,28-tetrakis(11-sulfanylundecyloxy)calix[4]arene (CALIX) sensitive to dopamine and confirmed its structure by (1)H NMR and mass spectrometry. Chemisorption of CALIX molecules or their mixtures with 1-dodecanethiols (DDT) or hexadecanethiols (HDT) resulted in formation of compact low permeable monolayers as revealed by cyclic voltammetry at presence of redox probe Fe(CN)(6). These self-assembled monolayers (SAMs) served as sensor for dopamine. Thickness shear mode acoustic method (TSM) has been used for study the interaction of dopamine with calixarene SAM. The admittance spectra of TSM transducer have been measured and used for simultaneous determination of the changes in series resonant frequency, f(S), and motional resistance, R(m), respectively. Addition of dopamine resulted in substantial decrease of f(S) and increase of R(m), which is evidence on increased viscoelastic contribution into the acoustic properties of the sensing layer. Limit of detection (LOD) for dopamine was 50 pM, which is much better in comparison with so far reported lowest LOD for dopamine-sensitive electrochemical sensors (20 nM). The sensor allowed discrimination between dopamine and epinephrine.