In Situ Reduction of Porous Copper Metal–Organic Frameworks for Three-Dimensional Catalytic Click Immunoassay

In this work, the reduced metal–organic frameworks (MOFs) that can function as a three-dimensional catalytic nanoreactor for copper-catalyzed azide–alkyne cycloaddition (CuAAC) click reaction have been fabricated for development of the immunoassay. In our design, MOFs with well-defined porosity are accessible to the substrates of CuAAC, while the substrates can diffuse in the pore channel. Moreover, the high-ordered structural alignments of MOFs are beneficial for integration of copper ions into the three-dimensional lattice. Therefore, upon exposure to reduction, the copper nodes in MOFs are transformed from Cu^II to Cu^I in situ to achieve spatiotemporal control, eliminating the primarily dissolution procedure. Furthermore, the reduced MOFs can serve as a powerful catalyst to facilitate the CuAAC click reaction, which can greatly reduce time and improve the reaction efficiency. In addition, the proposed immunoassay shows high analytical performance for hepatitis B virus surface antigen (HBsAg) quantification in the linear range of 0.03–2.0 ng mL^–1 with a detection limit down to 11.2 pg mL^–1. The new immunoassay has also been challenged in detection of clinical serum sample, and a good consistency can be found with the time-resolved fluorescence immunoassay (TRFIA) in clinics, signifying its promising potential in clinical diagnosis.