A Disposable Electrochemical Immunosensor Based on PDDA-functionalized Graphene/Gold Nanoparticles Composites for Detection of Inflammatory Cytokine Interleukin-22

A sandwich-format electrochemical immunoassay strategy was proposed for the single-protein detection of inflammatory cytokine, Interleukin-22 (IL-22). The capture anti-IL22 (Ab1) and detection anti-IL22(Ab2) were immobilized onto poly(dimethyldiallylammonium chloride)-functionalized graphene/gold nanoparticles nanocomposites (PDDA-G/AuNPs) modified indium tin oxide-coated glass (ITO) electrodes. When the immunosensor was incubated with sample antigens and biotin-modified Ab2 successively, streptavidin-modified horseradish peroxidase (HRP) was immobilized to produce the electrochemical signal by using o-phenylenediamine (OPD) and H2O2 as the electrochemical substrates. The linear ranges of IL-22 were from 5 to 5000pg mL−1 with the detection limits of 0.5 pg mL−1 (S/N=3), which is lower than that of the conventional ELISA. Experimental results demonstrated a ultrasensitive proposed immunosensor and revealed a selective and reproducible measurement of bioactive molecules in clinical diagnosis and therapy.