Label-assisted chemical adsorption triggered conversion of electroactivity of sensing interface to achieve the Ag/AgCl process for ultrasensitive detection of CA 19-9.

Efficient strategies in enhancing sensitivity are pivotal to ultrasensitive detection of tumor markers. In this work, based on the strategy of label-assisted chemical adsorption triggered conversion of electroactivity of sensing interface, a Ag/AgCl process was achieved to enhance sensitivity of the constructed sandwich-type amperometric immunosensor for ultrasensitive detection of carbohydrate antigen 19–9 (CA19-9). Briefly, polydopamine-Ag nanoparticles (PDA-Ag NPs), as signal precursor, combined with labeling antibody were served as labels and graphene oxide-melamine (GO-MA) substrate with chemical absorption capacity was applied as smart sensing interface. After successfully incubating labels, there was primitively no current response due to the poor conductivity between labels and electrode. However, in the presence of H 2 O 2 , Ag NPs from labels can be etched into Ag ions, which were adsorbed by GO-MA to form GO-MA-Ag as electroactive substrate. Then, the substrate exhibited a sharp and stable electrochemistry peak of solid-state Ag/AgCl process in the buffer containing KCl. The sensitivity toward detection of CA19-9 was notably enhanced based on the appearance of sharp peak. Under optimum conditions, the designed immunosensor demonstrated a wide working range from 0.0001 to 100 U mL−1 and an ultralow detection limit 0.032 mU mL−1. Thus, utilizing this strategy to construct immunosensor was highly promising in clinical diagnosis for ultrasensitive detection of tumor makers. Image 1 • GO-MA composite for chemosorption of Ag+ was used as smart sensing interface. • Ag/AgCl electrochemical process was realized via label-assisted chemosorption. • The immunosensor showed ultralow limit of detection 0.032 mU mL−1 for CA19-9. [ABSTRACT FROM AUTHOR]