Engineering of exosome-triggered enzyme-powered DNA motors for highly sensitive fluorescence detection of tumor-derived exosomes

Tumor-derived exosomes containing multiple proteins originating from parent cancer cells have emerged as biomarkers for cancer diagnosis. Herein, we propose a three-dimensional DNA motor-based exosome assay platform for the selective and sensitive detection of exosomes. The DNA motor used gold nanoparticle (GNP) tracks, consisting of fluorescein-labeled substrate strands and aptamer-locked motor strands. Recognition of the target protein on exosomes by its aptamer unlocked the motor strand and triggered the DNA motor process. Powered by restriction endonuclease , the motor strands autonomously walked along the GNP track. Each movement step cleaved one substrate strand and restored one fluorescein molecule. For exosome detection, the proposed method displayed a broad dynamic range acrossing 5 orders of magnitude with the detection limit as low as 8.2 particles/μL in PBS. The method also exhibited good selectivity among different tumor-derived exosomes and performed well in complex biological samples. The capability to profile exosomal surface proteins efficiently endowed our DNA motor great potential for developing a simple and cost-effective device for clinical diagnosis.