High-Sensitive Electrochemiluminescence C-Peptide Biosensor via the Double Quenching of Dopamine to the Novel Ru(II)-Organic Complex with Dual Intramolecular Self-Catalysis.

Here, a novel Ru(II)-organic complex (Ru-PEI-ABEI) with high electrochemiluminescence (ECL) efficiency was proposed to construct a sensitive quenching-typed ECL biosensor for C-peptide (C-P) measurement based on the double quenching effect of dopamine (DA). The high ECL efficiency of Ru-PEI-ABEI was originated from the dual intramolecular self-catalysis including intramolecular coreaction between polyethylenimine (PEI) and Ru(bpy)(mcbpy), and intramolecular ECL resonance energy transfer (ECL-RET) from N-(aminobutyl)-N-(ethylisoluminol) (ABEI) to Ru(bpy)(mcbpy), which would generate a strong initial ECL signal. Through sandwiched immunoreaction and 3D DNA walking machine, a certain amount of target C-P was converted to a large amount of intermediate DNA that could further trigger hybridization chain reaction (HCR) to introduce into massive DA which not only could quench the ECL of Ru(bpy)(mcbpy), but also quench the ECL of ABEI. Thus, the double quenching effect of DA would effectively quench the ECL of Ru-PEI-ABEI, leading to an obviously decreased final ECL signal. Thus, a sensitive quenching-typed ECL biosensor was constructed for C-P detection with a linear range from 50 fg mL to 16 ng mL and an estimated detection limit of 16.7 fg mL. The dual intramolecular self-catalyzed strategy and the double quenching strategy based on one quencher to the same luminous reagent proposed in this work would provide new thought in both ECL signal enhancement and quenching efficiency improvement.