Immunoelectrodes in protein detection: Comparison between glassy carbon and a semimetallic Ni/P thin film as binding support. Biological applications

Though immunoelectrodes can allow direct detection of very low protein amou nts (about 0.1 pmol) in vitro and in vivo, they are not yet widely used bec ause they need quality improvement Based on a few works devoted to the basi c electrochemical phenomenon occurring when antibobies are linked onto a so lid support and during antigen/antibody complex formation, we have coated t wo different supports with antibodies: the classical glassy carbon fiber or an epoxy plate covered with an amorphous semimetallic (nickel/phosphorus) thin film obtained by means of an electrochemical deposit. The antibody/ant igen complex formation induces direct and/or indirect ionic movements and a current flow through the conductive support toward a very low-noise and hi gh-sensitivity preamplifier stage in an I/V configuration. The proposed ele ctrochemical treatment (hydrophilization), applied to both carbon and Ni/P electrodes, improves antibody binding and reliability of the response to an tigens. The Ni/P probes present several advantages when compared to carbon fiber: better conductivity, possibility of surface quality control, and sem imetallic nature, making them unbreakable. Several applications were propos ed: somatostatin-14 detection with both carbon fiber and Ni/P plate electro des, and histamine detection in simple and complex fluid media. Dose-respon se curves and analysis of the results lead us to conclude that the obtained currents are directly related to the quantity of antigen.