Host-Guest Recognition-Mediated Supramolecular Aggregation-Induced Electrochemiluminescence of Iridium(III) Complexes for Nucleic Acid Bioassay

Currently reported aggregation-induced electroluminescence (AIECL) is usually based on the electrostatic integration of luminous monomers, and its application is still limited by the low ECL efficiency and poor structural stability of electrostatic integration-based AIECL emitters. Herein, host-guest recognition-mediated supramolecular AIECL was creatively developed to overcome the defects of electrostatic-integration-based AIECL. Cucurbit[8]uril (CB[8]) as the host recognized tris (2-phenylpyridine) iridium(III) [Ir(ppy)(3)] as the guest to form a novel supramolecular complex Ir-CB[8]. CB[8] can not only provide a large hydrophobic cavity to efficiently load Ir(ppy)(3) and enrich coreactant tripropylamine but also utilize its carbonyl-laced portals to form intramolecular hydrogen bonds to stabilize the supramolecular structure, so Ir-CB[8] revealed excellent AIECL performance. The AIECL emitter Ir-CB[8] coupled the efficient DNA walker to construct a sensing system for miRNA-16 detection. Au nanoparticles@norepinephrine (AuNPs@NE) trapped by single-strand S1 was developed to significantly quench the ECL emission of Ir-CB[8]. When the target microRNA-16 (miRNA-16) existed, H1 was opened and the sequential assembly from H2 to H7 was triggered, forming "windmill"-like DNA walker with six Pb2+-dependent leg DNA. The assembled DNA walker, which was centered on DNA structure, had high efficiency and biocompatibility and can cut S1 to keep the DNA fragment-carrying quencher AuNPs@NE away from the electrode surface, thus restoring the ECL emission of Ir-CB[8] and realizing ultrasensitive detection of miRNA-16. Supramolecular AIECL mediated by host-guest recognition provides a new way for constructing AIECL emitters with excellent structural stability and AIECL efficiency, and an Ir-CB[8] coupling "windmill"-like DNA walker builds a promising ECL-sensing system for bioassay.