Ultrasensitive Electrochemiluminescence Biosensor Based on DNA-Bio-Bar-Code and Hybridization Chain Reaction Dual Signal Amplification for Exosomes Detection.

Exosomes have received considerable attention as potent reference markers for the diagnosis of various neoplasms due to their close and direct relationship with the proliferation, adhesion, and migration of tumor. The ultrasensitive detection of cancer-derived low-abundance exosomes is imperative, but still a great challenge. Herein, we report an electrochemiluminescence (ECL) biosensor based on the DNA-bio-bar-code and hybridization chain reaction (HCR)-mediated dual signal amplification for the ultrasensitive detection of cancer-derived exosomes. In this system, two types of aptamers were modified on the magnetic nanoprobe (MNPs) and gold nanoparticles (AuNPs) with numerous bio-bar-code DNA, respectively, which formed "sandwich" structures in the presence of specific target exosomes. The "sandwich" structures were separated under magnetic field, and the numerous bio-bar-code DNA were released by dissolving AuNPs. The released bio-bar-code DNA triggered the HCR procedure to produce a good deal of long DNA duplex structure for embedding in hemin, which generated strong ECL signal in the presence of coreactors for ultrasensitive detection of exosomes. Under the optimal conditions, it exhibited a good linearly of exosomes ranging from 10 to 10 exosomes particle μL with limit of detection down to 5.01 exosome particle μL. Furthermore, the high ratio of ECL signal and minor change of ECL intensity indicated the good specificity, stability, and repeatability of this ECL biosensor. Given the good performance for exosome analysis, this ultrasensitive ECL biosensor has a promising application in the clinical diagnosis of early cancers.