Silver deposition directed by self-assembled gold nanorods for amplified electrochemical immunoassay

•An ultrasensitive nonenzymatic electrochemical immunosensor for HIgG detection was developed.•AuNRs were used to catalyze the deposition of silver.•Detection signal was greatly amplified by self-assembly of AuNRs and the subsequent silver enhancement.•This immunosensor exhibited a extremely low detection limit.

A novel electrochemical immunoassay was developed based on the signal amplification strategy of silver deposition directed by gold nanorods (AuNRs), which was in-situ assembled on the sandwich immunocomplex. The superstructure formed by the self-assembly of AuNRs provided abundant active sites for the nucleation of silver nanoparticles. In this pathway, the stripping current of silver was greatly enhanced. Using human immunoglobulin G (HIgG) as a model analyte, the ultrasensitive immunoassay showed a wide linear range of six orders of magnitude from 0.1 fg mL−1 to 100 pg mL−1, with the low detection limit down to 0.08 fg mL−1. The practicality of this electrochemical immunoassay for detection of HIgG in serum was validated with the average recovery of 93.9%. In addition, this enzyme-free immunoassay also has the advantages of acceptable reproducibility and specificity, and thus this immunosensing protocol can be extended to the detection of other low-abundant protein biomarkers.

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