Efficient DNA Walker Guided with Well-Regulated Interfacial Tracks for Ultrasensitive Electrochemiluminescence Biosensing.

Herein, highly efficient deoxyribonucleic acid (DNA) walking on electrode surfaces was realized by regulating DNA tracks, which was applied to construct an ultrasensitive electrochemiluminescent (ECL) biosensor for BCR/ABL fusion gene detection. The well-regulated DNA tracks were constructed supersandwich hybridization chain reaction of two DNA strands (L and L) to generate periodic linear dsDNA concatemers, where an exposed L domain closed with blocking strands (BS). The prepared DNA tracks were further assembled onto the surface of the Au nanoparticle-functionalized g-CN nanohybrid (Au@g-CN NHs)-modified electrode, achieving well-regulated interfacial tracks for the DNA walker. On this state, folic acid-labeled BS (FA-BS) were close to Au@g-CN NHs, performing a quenched ECL emission. With existence of the BCR/ABL fusion gene, the target combined two walking DNA strands (WD and WD) to form the bipedal DNA walkers, which walked on the well-regulated interfacial DNA tracks and replaced the FA-BS to light up the ECL emission, realizing DNA walker-based signal amplification. Compared to randomly constructed DNA tracks, the well-regulated DNA tracks reduced the kinetics barrier and fitted the step size of the DNA walker, thus promoting the DNA walking efficiency and decreasing the risk of interruption in the walking process. As a result, the designed DNA walker presented higher efficiency and capacity in signal amplification. Benefiting from this efficient DNA walker strategy, the ECL biosensor achieved sensitive detection of the BCR/ABL fusion gene with a detection limit of 0.18 fM. This smart strategy proposed a brief strategy to promote the working efficiency of the biosensor, which presented great application potential in clinical molecular diagnosis.