An electrochemiluminescence biosensor for ultra-sensitive detection of exosomes

Researchers at Nanjing University have developed an ultrasensitive electrochemiluminescence (ECL) biosensor to detect exosomes down to single particles based on multiple signal amplification. In this strategy, NiFe-tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy)32+) 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)32+ 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.