Electrochemiluminescence resonance energy transfer system fabricated by quantum state complexes for cardiac troponin I detection

•Quantum state complexes Au NCs-GQDs were successfully prepared.•Au NCs-GQDs produce higher ECL response benefit from ECL-RET.•The prepared Co3O4 NAs can accelerate the electron transfer.•A novel ECL biosensor for cTnI determination was designed.•The ECL biosensor exhibited a low detection limit and wide linear range. Electrochemiluminescence resonance energy transfer (ECL-RET) as an energy transfer model is used to explain signal quenching or enhancement phenomena. Establishing this model requires specific conditions including efficient electrochemiluminescence (ECL) emitters and energy donors with highly overlapping spectra and sufficient distance to complete the energy transfer. In this work, a novel ECL-based biosensor was proposed by utilizing graphene quantum dots (GQDs)-coupled gold nanoclusters (Au NCs) nanocomposites supported on a well-ordered Co3O4 nanoarrays (NAs) sensing substrate as signal labels. The as-synthesized Au NCs with controllable size by using glutathione as ligand showed stable ECL signal in triethylamine (TEA) aqueous solution. After coupling with GQDs, the obtained quantum state complexes (Au NCs-GQDs) are compact in space relation, and benefiting from resonance energy transfer and synergetic effect, thus producing higher ECL response. The prepared Co3O4 NAs exhibit consistent density orientation, which can not only work as an ideal substrate for capturing more immune molecules, but also act as a conductor to accelerate electron transport. This rational designed biosensor has been constructed for detecting cardiac troponin I (cTnI), a pivotal biomarker of acute myocardial infarction (AMI). Under optimal conditions, the biosensor showed a good ECL response of cTnI with a satisfactory linear range from 500 fg/mL to 20 ng/mL and an ultralow limit of detection of 354.2 fg/mL. With the excellent repeatability and stability, this method provides a clue for the expansion of the enhance-type ECL-RET model.