Layer-by-layer self-assembly of 2D graphene nanosheets, 3D copper oxide nanoflowers and 0D gold nanoparticles for ultrasensitive electrochemical detection of alpha fetoprotein

In this work, a novel and ultrasensitive label-free electrochemical immunosensor was developed for the quantitative detection of alpha fetoprotein (AFP). Thanks to the simple and versatile layer-by-layer self-assembly technology, the facile and firm immobilization of 2D graphene nanosheets (GS), 3D copper oxide nanoflowers (CuO NFs) and 0D gold nanoparticles (Au NPs) was achieved in the fabrication of the proposed immunosensor. A synergic effect amongst the electrocatalytic activity, conductivity and biocompatibility of GS, CuO NFs and Au NPs could provide high sensitivity for the label-free electrochemical immunosensor. The detection mechanism was based on monitoring of the electrocatalytic current response change towards the reduction of hydrogen peroxide (H2O2) when an immunoreaction occurred on the surface of the GS–CuO NFs–Au NPs modified electrode. Under optimal conditions, the designed immunosensor exhibited a wide linear range from 10−5 ng mL−1 to 102 ng mL−1 with a low detection limit of 5.3 fg mL−1 for AFP. It also displayed an electrochemical performance with good reproducibility, selectivity and stability, which could provide potential application in the clinical diagnosis of other tumor markers.