Multiple signal amplification electrochemiluminescence biosensor for ultra-sensitive detection of exosomes

Here, an ultrasensitive electrochemiluminescence (ECL) biosensor was developed to detect exosomes down to single particles based on multiple signal amplification. In this strategy, NiFe-tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy) 3 2+ ) on the electrode exhibited an excellent catalytic effect on the ECL reaction, significantly enhancing the ECL signal by approximately six-fold. In addition, the high affinity between the aptamer and CD 63 protein on the exosome surface released the RNA assembled into the DNA-RNA heteroduplex on the electrode. Duplex-specific nucleases activated DNA cleavage on DNA-RNA heteroduplex and initiated RNA recycling. Consequently, massive ferrocene (Fc)-DNA was detached from the electrode surface to recover the ECL emission of the NiFe-Ru(bpy) 3 2+ emitter. Benefiting from the multiple signal amplification, the fabricated ECL biosensor achieved a limit of detection for exosomes as low as 5 particles/μL and was successfully used for exosomes determination in serum. This sensor fabrication strategy will provide a universal and sensitive nano-platform for exosomes detection and enable the early diagnosis of related diseases. • An ultrasensitive electrochemiluminescence (ECL) biosensor is developed for detection of exosomes down to single particles. • NiFe-Ru(bpy) 3 2+ on electrode exhibits good catalytic effect in ECL system, effectively increasing the ECL signal by approx. 6 fold. • Due to the multiple signal amplification, a small amount of RNA can detach abundant Fc-DNA, leading to high sensitivity and low detection limit.