Sandwich-type immunosensor based on COF-LZU1 as the substrate platform and graphene framework supported nanosilver as probe for CA125 detection

CA125 is a tumor marker which mainly exists in ovarian, the detection for it with high sensitivity is conducive to improve the effectiveness of tumor prevention and control at early state. Multi-layer graphene oxide derivatives from graphene, and has poor conductivity and high stacked properties that limit its further application. Multi-layer reduced graphene oxide frame (MrGOF) was composed of single-layer graphene sheet and exhibited 3D structure with good dispersion, better conductivity and electrochemical properties after multi-layer graphene oxide underwent alkaline peeling and thermally reduction, the modified graphene are easy to load and combine functional groups and metal nanoparticles. Covalent organic frameworks (COFs) presents a stable frame and through covalent bond connection and has porous properties to adsorb biomolecules, which allows the immobilization of antibody molecules by the porosity and improve the sensitivity of the detection in sensing field. Through the adsorption of COFs for antibody and the probe labeled with functional graphene, we constructed a sandwich type immunosensor with the new material COF-LZU1 as the platform to anchor the CA125 first-antibody and MrGOF combined with amino group and loaded with silver nanoparticles (AgNPs) as the probe to detect tumor marker CA125. The linear range of detection was from 0.001 U/mL to 40 U/mL, with the detection limit was calculated to be 0.00023 U/mL (S/N =3). The prepared immunosensor showed a good application ability for real human serum, which can be attributed to the adsorption of COF-LZU1 for the CA125 first-antibody, and ability to deliver electrons and signal amplification of AgNPs anchored on the sheet structure of MrGOF.