Ultrasensitive electrochemical detection of secretoneurin based on Pb2+-decorated reduced graphene oxide-tetraethylene pentamine as a label

In this work, a novel electrochemical immunosensor for the detection of secretoneurin (SN), which uses metal ion functionalised reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) as a label, is reported for the first time. rGO-TEPA contains a large number of amino groups, which makes it an ideal templet for the loading of metal ions. rGO-TEPA-Pb2+ was employed to immobilise secondary secretoneurin (SN) antibody (Ab2), and the resulting nanocomposite (Ab2-rGO-TEPA-Pb2+) was used as a trace tag for signal amplification. A modified electrode consisting of functionalised graphene nanosheets (Au@GS) was used as a substrate to immobilise the antibodies. Under the optimal conditions, the immunoassay exhibited high sensitivity, acceptable stability and reproducibility with a wide linear range from 0.001 to 100 ng mL−1 (R=0.996), and an ultra-low detection limit of 0.33 pg mL−1 (S/N=3). Furthermore, the immunosensor could be employed to detect SN in clinical serum samples. The proposed sensing strategy enriches the electrochemical immunoassay and exhibits potential for the point-of-care diagnostic application of the clinical screening of biomarkers.