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Aggregation-Induced Electrochemiluminescence Bioconjugates of Apoferritin-Encapsulated Iridium(III) Complexes for Biosensing Application

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journal contribution
posted on 21.12.2020, 20:14 by Lei Yang, Xu Sun, Dong Wei, Huangxian Ju, Yu Du, Hongmin Ma, Qin Wei
An intriguing aggregation-induced electrochemiluminescence (AIECL) bioconjugate was fabricated by encapsulating fac-tris­(2-phenylpyridine)­iridium­(III) complexes [Ir­(ppy)3] in the apoferritin (apoFt) cavity for biosensing application. Based on the unique pH-dependent disassembly/reassembly characteristic of apoFt, approximately 44.3 molecules of Ir­(ppy)3 aggregated in the single cavity through both intermolecular π–π-stacking interactions and hydrogen bonds that efficiently restricted the intramolecular motions to trigger the AIECL effect. Compared to monomers, Ir­(ppy)3 aggregates performed 5.3-fold-enhanced ECL emission using tri-n-propylamine (TPrA) as a coreactant. The fabricated Ir­(ppy)3@apoFt bioconjugate was flexibly labeled with a detection antibody to act as a transducer for the immunosensor construction. To further catalyze the ECL reaction between the reductive TPrA and the oxidative Ir­(ppy)3+• radicals, a conductive and electroactive substrate of Fe2N and gold nanoparticle-codecorated reduced graphene oxide (Fe2N/rGO/Au) was established to incubate the capture antibody. Therefore, a “signal on” immunosensor was developed for sensitive assay of cytokeratin 19 fragment 21–1 (CYFRA 21–1), in which good linearity ranging from 1 pg/mL to 50 ng/mL with a low detection limit of 0.43 pg/mL (S/N = 3) was obtained. This study shares with an inspiration of using apoFt to design iridium­(III)-based AIECL emitters, which will expand more possibilities of organic iridium­(III) complexes in establishing innovative ECL immunoassays.

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