A specific identification platform based on biscuit-like bismuth nanosheets for label-free electrochemical immunosensor.

A label-free electrochemical immunosensor based on the biscuit-like bismuth nanosheets (BiNSs) and multi-wall carbon nanotubes-chitosan-gold nanoparticles (MWCNTs-Chit-AuNPs) was constructed for the detection of human immunoglobulin G (hIgG). The biscuit-like BiNSs prepared by one-step aqueous phase reduction method had a large electroactive surface area, 1.7 times that of bare glassy carbon electrode (GCE), which could load more antibodies and were used as a larger platform for the specific identification of antigens and antibodies. In addition, MWCNTs and AuNPs with good conductivity could be used to regulate the sensing interface, which promoted electron transfer greatly. Moreover, the AuNPs could stably anchor anti-hIgG by the affinity interaction between amine group of antibody and AuNPs, which greatly increased the number of anti-hIgG attached to the sensing platform. Under the optimal conditions, the proposed immunosensor exhibited excellent analytical performance for hIgG with a wide linear response of 0.01-1000 ng/mL and a low detection limit of 4.26 pg/mL. The electrochemical immunosensor exhibited favorable reproducibility, excellent specificity and high storage stability. Additionally, the immunosensor could be applied to determining hIgG in human serum samples as well. Considering these advantages, the electrochemical immunosensor has the potential application in clinical diagnosis.