Split-type electrochemiluminescence immunosensor for h-FABP: Performance enhancement through site-oriented antibody...

The analytical accuracy of immunoassays heavily depends on antibody-antigen recognition, but the random immobilization of antibodies on the sensing platform severely hinders recognition. This article introduces a recognition-detection split electrochemiluminescence (ECL) immunosensor with a cobalt-based metal-phenol network as a site-oriented immobilization platform. Cobalt ions enriched on gold-nanoparticle-modified magnetic beads play a significant role in anchoring the structural domains of the histidine-rich portion of the fragment crystallizable region in the antibody. Hence, the precise immobilization of the antibody and highly effective targeting of the antigen are achieved. In addition, luminescent metal-organic framework nanoreactors based on intra-reticular charge transfer mechanism are synthesized. The "two-in-one" nanoreactors integrating luminophores and co-reactants exhibit better intrinsic ECL efficiency and extrinsic ECL intensity than the luminophore alone. Magnetic-separation-based sandwich-type identification overcomes errors associated with solid-state heterogeneous incubation. The developed biosensor achieves a limit of detection of 0.3 pg/mL (S/N = 3) for heart-type fatty acid binding proteins in the detection range from 0.5 pg/mL to 100 ng/mL. The proposed "two-in-one" approach can guide the development of efficient ECL emitters, and identification based on the metal-phenol network provides an efficient route for sensing applications.