Triggered hairpin switch and in situ nonlinear hybridization chain reaction enabling label-free electrochemiluminescent detection of BCR/ABL fusion gene

Herein, a highly specific and ultrasensitive strategy is presented for label-free electrochemiluminescent (ECL) detection of BCR/ABL fusion gene via triggered hairpin switch and in situ nonlinear hybridization chain reaction (HCR) signal amplification. A droplet of mixture containing nonlinear HCR system is dropped on the gold electrode surface modified with capture probes, in which a trigger DNA in the hairpin switch initiates self sustained assembly of double-stranded substrates into dendritic nanostructures. The presence of BCR/ABL fusion gene leads to the open of hairpin switch and the growth of dendritic nanostructures onto electrode surface. The dsDNA grooves of the nanostructures bind with numerous ECL signal indicators Ru(phen)(3)(2+), resulting in exponential amplification of ECL signal output. The developed biosensor achieves a low detection limit of 5.49 fM towards BCR/ABL fusion gene, and can distinguish single base-mismatched target. And the biosensor further applied in complex matrix without the decline of analytical performance. In addition, this method has the advantages of enzyme-free and label-free assay system. These advantages make the sensor be a promising candidate in the determination of fusion gene for medical diagnostics.