Facile preparation of iridium-based AIE polymer dots for sensitive electrochemiluminescence immunoassay of CD44 protein

초록

The development of aggregation-induced emission (AIE) luminophores is a fascinating and promising topic in electrochemiluminescence (ECL) bioanalysis. Herein, the AIE-active but water-insoluble [Ir(bt)₂(acac)] (bt = 2-phenylbenzothiazole, acac = acetylacetonate) was encapsulated within poly(styrene-maleic anhydride) (PSMA) using a simple nanoprecipitation method. This encapsulation strategy could effectively limit the free motion of Ir(bt)₂(acac) and trigger the aggregation-induced electrochemiluminescence (AIECL) effect. The water dispersibility and ECL intensity of Ir(bt)₂(acac)-polymer dots (IrPdots) were greatly improved compared to equivalent amounts of Ir(bt)₂(acac) alone. More importantly, unlike Ir(bt)₂(acac), the IrPdots possess carboxyl groups, allowing them to be conjugated with biomolecules for bioanalytical applications. Consequently, a sandwich ECL immunosensor for the sensitive detection of CD44 was constructed using the prepared IrPdots-labeled detection antibody (Ab2) as the ECL probe and polyaniline nanorods (PANI NRs) as the substrate that provided a large electroactive surface for immobilizing capture antibody (Ab1). Under optimized experimental conditions, a good linear relationship was observed between the logarithm of ECL intensity and the CD44 concentration, ranging from 0.1 pg/mL to 50 ng/mL, with a detection limit as low as 77 fg/mL. This work introduces a method for the preparation of Pdots containing AIE-active cyclometallated iridium complexes, potentially broadening the application of these water-insoluble but highly AIE-active iridium complexes in aqueous bioassays. © 2025 Elsevier B.V.

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