A highly sensitive and selective label-free impedimetric immunosensor for the detection of interleukin-6 based on AuNPs@pDA@NiCoS@MoS nanocomposite.

A highly sensitive and selective label-free impedimetric immunosensor based on AuNPs@pDA@NiCoS@MoS nanocomposite modified on the surface of a screen-printed electrode (SPE) was designed for the detection of interleukin-6 (IL-6). The distribution of NiCoS nanoparticles on MoS nanosheets was able to prevent them from agglomerating. The polydopamine (pDA) layer was coated on the surface of NiCoS@MoS nanosheets by self-polymerization, which improved the stability and biocompatibility of the nanomaterial. The excellent reduction ability of pDA promoted the synthesis of gold nanoparticles (AuNPs), which increased the amount of antibody adsorption and the conductivity of the material. Finally, the antibody (Ab) of IL-6 was immobilized on the surface of AuNPs@pDA@NiCoS@MoS nanocomposite. Electrochemical impedance spectroscopy (EIS) was used to detect the change of impedance before and after the immune response between Ab and IL-6 antigen (IL-6). Under the optimal experimental conditions, the relative change in impedance and the logarithmic concentration of IL-6 showed a good linear relationship in the range 1.00 to 1.00 × 10 pg/mL, with a low detection limit of 0.97 pg/mL. In addition, the proposed immunosensor performed with good reproducibility, stability, and specificity. It was successfully applied to the determination of IL-6 in patient's serum samples of head and neck carcinoma with recoveries of 98.40% to 106.5%. To sum up, the proposed label-free impedimetric immunosensor was successfully constructed for IL-6 detection in real samples.