Gold Nanoparticle-Based Artificial Antibodies as Stable Substitutes for Antibodies in the Immunoassay.

Sandwich enzyme-linked immunosorbent assay (ELISA) is a widely used powerful method to detect antigens in complicated environments, due to the high sensitivity and specificity of monoclonal antibodies. Yet, the intrinsic instability of antibodies limits the applications of sandwich ELISA. To overcome the shortcomings of antibodies, we previously demonstrated that a class of gold nanoparticle (AuNP)-based artificial antibody, named goldbody, can be created by "Goldization" technology, i.e., reconstructing the fragments of antibodies on AuNPs. Goldbody has the same binding specificity as the original antibody, but has a much better stability. However, it is still a big challenge to design matched goldbody pairs to develop a sandwich ELISA entirely based on goldbodies. Herein, an anti-EGFR goldbody is designed and synthesized by reconstructing ("Goldization") the "dimerization arm" fragment of EGFR on AuNPs. As expected, this new anti-EGFR goldbody binds to EGFR at a site far away from where the previously developed one binds, allowing the two anti-EGFR goldbodies to bind the same EGFR simultaneously and qualify as a matched pair. Subsequently, a goldbody-based sandwich ELISA is developed, and the goldbodies in the ELISA kit can be used for the detection of EGFR even after preheatment at 100 °C, demonstrating the excellent stability of goldbody.