Fig 1. The principle of the conventional and in-house Eu⁺³-NP-based CA15-3 lectin assays.

In the conventional CA15-3 immunoassay, the capture and tracer mAbs bind to the protein and glycan epitopes of CA15-3. Alternatively, in the lectin assay, the CA15-3 is captured with mAbs and detected with lectins, which have been coated on the surface of Eu³⁺-NPs. This method allows multivalent binding of the tracer to the glycan moieties of BC-CA15-3.