Antioxidant Cascade Modulated Electrochemiluminescence by a Biomimetic Metal–Organic Framework with Dual Enzymatic Activity for Disease Marker Immunoassays

High-performance electrochemiluminescence is a significant approach for the examination of disease biomarkers, and the utilization of innovative electrochemiluminescence detection systems represents a viable strategy to enhance the efficacy of ECL analysis. In this work, the biomimetic engineering metal-organic framework (MOF-818) has realized the ultrasensitive ECL immunoassay of disease markers based on the guidance of the free radical scavenging strategy provided by the antioxidant cascade. Initially, we synthesized a hydrogen-bonded organic framework (HOF) consisting of luminol and three active ligands based on simple room-temperature self-assembly. The luminol-HOF (L-HOF) showed more stable and brighter ECL luminescence activity than the monomer due to the nano-confinement enhancement of the coordinated luminol units. Subsequently, MOF-818 with biomimetic superoxide dismutase (SOD) and catalase (CAT) activities were recruited for the first time as quenching agents for sandwich immunoassay mode. The enzyme activity leads to the reverse transformation of superoxide anion radicals (O2-) and further antioxidant decomposition, decreasing in the responsiveness of luminol ECL signals. Using carcinoembryonic antigen (CEA) as an analytical model, a detection limit of 0.457 pg/mL was obtained within a detection range of 0.001-50 ng/mL. We believe that this novel sandwich sensing model based on enzyme activity provides a meaningful potential tool for precise detection, expanding the broader application of nanoenzymes in analysis.