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

Abstract

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.

Electronic Metal–Support Interactions for Electrochemiluminescence Signal Amplification

“…To better understand the origin of the enhanced electrocatalytic activity of Au/LDH-O v /ITO, electrochemically active surface area (ECSA) was measured via CV using [Fe­(CN) 6 ] 4–/3– as the redox indicator (Figures S12–S15 and B) . According to the Randles–Sevcik equation, the slop of Au/LDH-O v /ITO was higher than that of Au/LDH/ITO.…”

Aggregation-Induced Emission in Electrochemiluminescence: Advances and Perspectives

“…A very innovative approach has recently been shown by Wei et al that produced an AIECL fluorophore by confining molecules of fac-tris(2-phenylpyridine) iridium(III) (Ir(ppy) 3 ) [68]. The aggregation of around 44 molecules within the apoferritin (apoFt) cavity caused a 5.3-fold enhancement of the ECL emission compared to the monomer signal.…”

“…Copyright 2020 American Chemical Society LOD (0.43 pg mL −1 ). This type of bioconjugate approach can help to overcome the limited colloidal stability of some strongly insoluble AIECL luminogens [68].…”

Molecular Engineering of Polymer Dots for Electrochemiluminescence Emission

“…Electrochemiluminescence (ECL) is a light emission process from the excited state of luminophores generated during electrochemical reactions. − Generation of high-performance ECL is dependent on the synergism between the initial electrochemical excitation and the succedent chemiluminescence . A variety of novel enhancement strategies have been developed to improve the performance, for instance, self-enhanced ECL, crystallization-induced enhanced ECL (CIE-ECL), and aggregation-induced ECL (AIECL). − These strategies can be divided into two basic categories, namely, electron-transfer-based enhancement strategy and luminescence efficiency-based enhancement strategy. A self-enhanced ECL system adopts a short-range intramolecular electron-transfer strategy via the coassembly of luminophores and coreactants into the framework .…”