Immunosensing of carbohydrate antigen 19–9 based on covalent organic framework loaded Prussian blue as signal amplification platform

Immunosensing of carbohydrate antigen 19–9 (CA 19–9) by using covalent organic framework (COF) loaded Prussian blue (PB) as signal amplification platform was developed. Firstly, two-dimensional (2D) vinyl-rich COFTAGH-Dva (TAGH, triaminoguanidine hydrochloride; Dva, 1,4-benzenedicarboxaldehyd) was prepared to load PB, and further the Ab2 was assembled through the "click" reaction between –SH of Ab2 and vinyl of COFTAGH-Dva to construct the beacon complex of PB/COFTAGH-Dva/Ab2. Another 2D COFTp-BD (Tp, 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde; BD, benzidine) rich in –NH- groups was combined with AuNPs to form AuNPs/COFTp-BD by in-situ reduction method, and then Ab1 was assembled through Au-S bond. In the process of electrochemical immunosensing, AuNPs/COFTp-BD was first assembled on glassy carbon electrode (GCE) to form AuNPs/COFTp-BD/GCE, which then adsorbed Ab1 by Au-S bond, and specifically and quantitatively captured CA 19–9 and the beacon complex of PB/COFTAGH-Dva/Ab2. With the increase of antigen CA 19–9, the redox peak signal of Fe2+/Fe3+ derived from PB in the beacon complex of PB/COFTAGH-Dva/Ab2 gradually increased. The linear range of the electrochemical immunosensor was 0.01–150 U/mL (U/mL represents the concentration of CA 19–9, which is the number of units of CA 19–9 per 1 mL volume) and the detection limit was 0.003 U/mL. This work provides a reference for constructing high-performance electrochemical immunosensor probes by using good biocompatibility and electroactive materials loaded on non electroactive COFs.