Proximity hybridization-regulated electrochemical stripping of silver nanoparticles via nanogold induced deposition for immunoassay

A simple and disposable electrochemical immunosensor was developed for sensitive and selective detection of a protein biomarker via target-induced proximity hybridization and electrochemical stripping analysis of silver nanoparticles (AgNPs). The immunosensor was prepared by assembling single-stranded DNA modified gold nanoparticles (ssDNA@AuNPs) on a graphene oxide modified disposable screen-printed carbon electrode (SPCE). In the presence of a target protein and two DNA-labeled antibodies, the proximate complex formed in homogeneous solution could hybridize with the assembled DNA to take away AuNPs, which decreased AuNP-catalyzed deposition of AgNPs on the immunosensor surface, and thus the anodic stripping signal. The proposed method avoided the interference of dissolved oxygen. Using the carcinoembryonic antigen (CEA) as a model analyte, this method showed a linear range of four magnitude orders with a detection limit down to 3.9 pg mL−1. The electrochemical immunosensor possessed preparation convenience, good stability and high sensitivity, and could be extended to sensitive biosensing of other analytes, showing potential application in point-of-care testing.