A robust composite hydrogel consisting of polypyrrole and β-cyclodextrin-based supramolecular complex for the label-free amperometric immunodetection of motilin with well-defined dual signal response and high sensitivity

The label-free amperometric immunosensor is a simple, convenient and reliable method for the detection of diseases markers. Its performance heavily relies on the properties of the sensing substrate. In this paper, we proposed a robust composite hydrogel that consists of polypyrrole and vinyl ferrocene/mono-aldehyde β-cyclodextrin (β-CD) complex as a sensing and immobilizing substrate. Surprisingly, it was observed that the microstructure of the hybrid hydrogel could be well regulated by the feed ratio of vinylferrocene and so are the electrochemical properties. Depending on the dual electrochemical active compositions, a large loading capacity of antibodies and meanwhile the excellent conductivity, the square wave voltammetry results of the optimized immunosensor for the detection of motilin exhibited a well-defined dual signal response, with a wide linear range both from 10 pg mL−1 to 100 ng mL−1 for motilin, and an ultralow limit of detection of 6.29 pg mL−1 and 2.73 pg mL−1. More importantly, the immunosensor exhibited an especially sensitive response with the slope value as high as 31.342 and 25.751 respectively, which makes great sense in the practical diagnosis.