Ultrasensitive multiplexed protein biomarker detection based on electrochemical tag incorporated polystyrene spheres as label

Multiplexed electrochemical immunosensor was developed for ultrasensitive detection of interleukin-6 (IL-6) and interleukin-17 (IL-17) using electrochemical tag incorporated polystyrene sphere (PS) as label. The electrochemical tag contained in the PS, cadmium ion (Cd2+) or ferrocene (Fc), could be effectively detected by square wave voltammetry (SWV) after dissolving the PS with organic solvent to release the electrochemical tags onto electrode surface. With the immobilization of two different antibodies onto the PS surface, respectively, the position and intensity of the current peaks due to the two electrochemical tags could reflect the identity and level of the corresponding protein biomarkers. The significant amount of electrochemical tags incorporated into PS greatly enhanced the detection sensitivity. The proposed immunoassay exhibited high sensitivity and good selectivity for the detection of IL-6 and IL-17. The response current was linear to the logarithm concentrations of IL-6 and IL-17 in the range from 1 pg/mL to1 ng/mL and 2 pg/mL to 1 ng/mL, respectively. The detection limits of IL-6 and IL-17 were 0.5 and 1 pg/mL (S/N = 3). These results suggested that this electrochemical immunosensor would be widely applied for clinical screening of protein biomarkers.