Introducing graphitic carbon nitride nanosheets as supersandwich-type assembly on porous electrode for ultrasensitive electrochemiluminescence immunosensing

Biomarkers in blood or tissue provide essential information for clinical screening and early disease diagnosis. However, increasing the sensitivity of detecting biomarkers remains a major challenge in a wide variety of electrochemical immunoassays. Herein, we present an electrochemiluminescence (ECL) immunosensing strategy with 1: Nn amplification ratio (target-to-signal probe) for biomarkers detection on a porous gold electrode. The high porosity of the electrode surface provides enough bonding sites for capturing the target biomolecules and thus many DNA labels can be introduced. On the basis of this concept, a great number of graphitic carbon nitride (g-C3N4) nanosheets are employed to create a supersandwich-type assembly on a porous electrode via the DNA hybridization process. Furthermore, compared with the traditional sandwich immunoassay (the ratio of target-to-signal probe is 1 : 1), the supersandwich construction can introduce a large number of signal probes, thus resulting in a highly improved sensitivity. The proposed ECL immunosensor exhibits an excellent performance in a concentration range from 0.01 fg mL−1 to 1 μg mL−1 with an ultralow detection limit of 0.001 fg mL−1 (S/N = 3) and excellent selectivity. This sensing strategy could be developed into a real-time assay for the disease-related molecular targets, with many practical applications in biotechnology and life science. Graphitic carbon nitride (g-C3N4) nanosheets are employed to create a supersandwich-type assembly on a porous electrode via the DNA hybridization. Compared with the traditional sandwich immunoassay (the ratio of target-to-signal probe is 1 : 1), the supersandwich construction can introduce a high number of signal probes, thus resulting in a highly enhanced ECL signal (∼20 times). [Display omitted] •An ECL immunosensor with 1: Nn amplification ratio was developed.•A porous Au electrode provides plenty bonding sites for enriching target molecules.•The supersandwich immunosensor showed 20-fold increase in ECL signal.•The supersandwich sensing strategy exhibited outstanding selectivity.