Calixarene-based porous coordination compound as microreactors: Enrichment-enhanced electrochemiluminescence of iridium(III) complex for bioanalysis

Abstract

Improving the electrochemiluminescence (ECL) efficiency of iridium complexes such as Ir(ppy)3 is still valuable for expanding their applications in the ECL field. Herein, a calixarene-based porous coordination compound (referred to SWU-1) with ordered pore structure and large porosity was innovatively developed as microreactors, which not only acted as a carrier to efficiently load Ir(ppy)3 on its surface and further achieve aggregation-induced ECL (AIECL) of Ir(ppy)3, but also enriched coreactant tripropylamine (TPrA) in its hydrophobic cavity. As a result, the prepared Ir@SWU-1 NCYLs exhibited a significantly improved ECL efficiency and aqueous dispersion as compared to Ir(ppy)3. The complex of Ir@SWU-1 NCYLs and polyethyleneimine (PEI) was used to modify the electrode for assembling Pt nanoparticles and further capturing hairpin H2·H2O2 was introduced into test solution to quench the ECL emission from Ir@SWU-1 NCYLs/TPrA system, leading to a signal-off state. When the target amyloid-β oligomers (AβO) existed, amounts of single-strand S1 were released from the target cycle, triggering the strand displacement amplification (SDA) on the magnetic beads. The single-strand ST output from the SDA reaction would open hairpin H2 on the electrode surface and initiate the rolling circle amplification (RCA) reaction so that scores of long chains rich in G bases were generated and further captured hemin to form hemin/G-quadruplex. With the consumption of H2O2 by hemin/G-quadruplex, the ECL signal was recovered, thus achieving the sensitive detection of AβO. This work developed novel ECL microreactors to load Ir(ppy)3 and enrich coreactant TPrA. The Ir@SWU-1 NCYLs with high ECL efficiency and excellent dispersity provided a fascinating ECL sensing platform for bioanalysis, expanding the application of iridium(III) complexes in ECL field.