Label-free tri-luminophores electrochemiluminescence sensor for microRNAs detection based on three-way DNA junction structure

A label-free microRNAs (miRNAs) electrochemiluminescence sensor was developed based on the synergistically enhanced ECL signal using novel ECL nanomaterial assembled by tri-luminophores perylenetetracarboxylic acid (PTCA) graphite-like carbon nitride nanosheet (g-C3N4 NS) and graphene carbon quantum dots (GQDs). The ECL intensity of our proposed nanocomposites increased significantly, by taking advantages of the synergistic promotion ECL mechanism of PTCA g-C3N4 and GQDs. Meanwhile, a three-way junction (TWJ) structure was introduced into the sensor design, whose conformation can be specifically induced in the presence of target miRNA. Thus, the formation of TWJ structure can hinder the contact between the co-reactant Na2S2O8 in the solution phase and the luminescent substrate, which produce a quenched ECL signal. Our proposed ECL biosensor provided a highly sensitive detection of miRNA-21 with a detection limit of 96 aM ranging from 100 aM to 1 nM. Furthermore, this ECL sensing system was able to successfully distinguish the target RNA from its homologous family and presented a promising response in human real samples. With excellent properties, the proposed ECL biosensor provided an efficient and ultrasensitive method for miRNAs detection.