Design of electrochemical immunosensors using electro-click chemistry. Application to the detection of IL-1β cytokine in saliva

Abstract

Electro-click methodology was employed to prepare an electrochemical immunosensor for the cytokine interleukin 1β (IL-1β). The strategy involved binding of ethynylated IgG to azide-MWCNTs modified electrodes by Cu(I) catalyzed-cycloaddition reaction where the catalyst was electrochemically synthesized. This electro-click protocol is significantly faster and greener than the methods for catalyst generation through chemical reduction. The oriented immobilization of the capture antibody onto IgG-MWCNTs conjugates allowed the preparation of a sandwich-type immunosensor using biotinylated anti-IL-1β as detector antibody labeled with alkaline phosphatase-streptavidin (AP-strept). Differential pulse voltammetric transduction through the 1-naphthylphosphate/1-naphthol system was carried out. The analytical characteristics achieved with the electrochemical immunosensor showed a calibration curve exhibiting two linear ranges between 10 and 200 pg mL−1 (r2 = 0.998), and from 200 to 1200 pg mL−1 (r2 = 0.998), and a LOD value of 5.2 pg mL−1, an improvement compared with those claimed for commercial ELISA kits. In addition, the assay time was at least one hour shorter. Excellent performance was observed in the determination of IL-1β in saliva with no need for sample treatment, and by simple interpolation using a calibration plot constructed with standard solutions of the target cytokine.