In situ amplification based on assembly of aptamer sandwiches on nanochannels for ultrasensitive detection of exosomes

Exosomes hold tremendous potential as promising biomarkers for the early diagnosis of cancer. The urgent need for sensitive identification of cancer cell-derived exosomes has emphasized the importance of fabricating innovative approaches. In this work, we propose a novel in situ amplification strategy for ultrasensitive detection of cancer cell-derived exosomes based on the assembly of aptamer sandwiches on nanochannels. Specifically, the nanochannels are functionalized with aptamers targeting the transmembrane receptor protein CD63 to enable selective capture of exosomes. Meanwhile, the aptamers specific to membrane protein EpCAM are employed as anchors for binding with the targeted exosomes. This orchestrated interaction leads to the assembly of aptamer sandwiches, initiating a TdT-mediated polymerization reaction, thereby facilitating in situ amplification. Consequently, ultrasensitive, highly specific, and accurate detection of exosomes can be achieved, with a linear detection range from 2.06 x 103 to 2.06 x 108 particles/mL and a detection limit as low as 6.87 x 102 particles/ mL. Moreover, the method shows satisfactory anti-interference capacity for the detection of exosomes in real serum samples, indicating potential applications in early clinical diagnosis of cancer.