A Host-Guest Interaction-Based and Metal-Organic Gel-Based Biosensor with Aggregation-Induced Electrochemiluminescence Enhancement for Methyltransferase Assay.

Metal-organic gels (MOGs) are new soft materials with the characteristics of high colloidal stability, superb luminescence properties, and facile synthesis. Herein, we develop for the first time a host-guest interaction-based and MOG-based biosensor with aggregation-induced electrochemiluminescence (ECL) enhancement for M.SssI methyltransferase (M.SssI MTase) assay. This biosensor employs a MOG as the luminophor and potassium persulfate as the coreactant, and the formation of the Ag-MOG from the aggregation of silver nanoclusters can induce significant ECL enhancement. Two complementary single-stranded DNAs (ssDNAs, i.e., biotinylated DNA-1 and Fc-labeled DNA-2) that contain specific recognition sequence 5'-CCGG-3' can form a double-stranded DNA (dsDNA) probe. In the absence of M.SssI MTase, the dsDNA probe will be digested by restriction endonuclease HpaII, leading to the release of Fc from magnetic beads (MBs). The β-CD can specifically recognize the released Fc through guest-host interaction, resulting in the quenching of an ECL signal. In contrast, the presence of M.SssI MTase enables the formation of fully methylated dsDNA, which cannot be cleaved by HpaII, making Fc remain on the MB surface and consequently generating an improved ECL signal. This biosensor can specifically detect M.SssI MTase with a linear range of 0.05-100 U mL and a limit of detection of 3.5 × 10 U mL, and it enables accurate detection of M.SssI MTase in human serum. In addition, it can be used for inhibitor screening, with wide applications in drug discovery and disease diagnosis.