Signal-enhanced electrochemiluminescence strategy using iron-based metal-organic frameworks modified with carboxylated Ru(II) complexes for neuron-specific enolase detection

The preparation of highly efficient electrochemiluminescence (ECL) illuminants is an effective method to improve the sensitivity and repeatability of ECL immunoassay. In this study, we prepared an ECL immunoassay for efficient and sensitive detection of neuron-specific enolase (NSE) by linking carboxylated Ru(bpy)32+ to an iron-based metal-organic framework (NH2-MIL-88 (Fe)) via an amide bond as an ECL signal probe. NH2-MIL-88 (Fe) possesses a large number of amino groups that can catalyze the co-reactant S2O82−, which generates abundant reaction intermediates SO4•- around Ru(dcbpy)32+, reduces the loss of material transport and energy transfer between SO4•- and Ru(dcbpy)32+, and significantly enhances the ECL signal. We used polyaniline-intercalating vanadium oxide (PVO) nanosheets as the substrates to capture NSE owing to the large specific surface area and extraordinary conductivity of the nanosheets. Similarly, PVO nanosheets also possess abundant amino groups, which can act as co-reaction promoters to catalyze the reaction of S2O82− to SO4•-, enhancing the ECL signal of the immunoassay. Therefore, we constructed a dual-enhanced ECL immunoassay with Ru(dcbpy)32+/NH2-MIL-88 (Fe) and PVO as the signal probe and substrate, respectively, which exhibited excellent sensitivity and selectivity for detecting NSE. This study offers an effective strategy for ultrasensitive detection of trace proteins using ECL immunoassays.