Electrochemically deposited cobalt bis(dicarbollide) derivative and the detection of neuroblastoma markers on the electrode surface

A cobalt bis(dicarbollide) derivative deposited onto the surface of a graphite electrode through an electrochemically oxidized o-phenylenediamine unit (pCB-oPD) is proposed for the detection of catecholamine metabolites, namely homovanillic acid (HVA) and vanillylmandelic acid (VMA). These metabolites are diagnostic markers of neuroblastoma. The set of electrochemical techniques, electrochemical impedance spectroscopy (EIS), potentiometry, and differential pulse voltammetry (DPV), makes it possible to evaluate the options of the individual and simultaneous detection of metabolites. The values of association constants that were found between the pCB-oPD attached to the electrode surface and the metabolites showed a high affinity to HVA (2.5 × 105) compared to VMA (4.3 × 104). The binding of the metabolites to the pCB-oPD-modified electrode allows the differentiation of VMA and HVA in the mixture, which can be of practical interest.