A catalytic molecule machine-driven biosensing method for amplified electrochemical detection of exosomes

Nowadays, exosomes that carry abundant information have attracted increasing attention as potent biomarkers of liquid biopsy and ideal candidates for early diagnosis and treatment of cancers. In this work, we propose a "principle-of-proof" biosensing method for amplified electrochemical detection of exosomes by using HepG2-derived exosomes as models. Specifically, target exosomes are enriched on anti-CD63-functionalized immunobeads and then recognized by a DNA chain containing CD63 aptamer region, which subsequently initiates a catalytic molecule machine that relies on cascade toehold-mediated strand displacement reaction. Benefiting from high efficiency of the molecule machine, the method shows a linear range from 1 × 10⁵ to 5 × 10⁷ particles/mL and a detection limit of 1.72 × 10⁴ particles/mL toward target exosomes, better than most existing detection methods. Moreover, the method demonstrates a high specificity even in serum samples and suggests a potential use in clinic, which may provide sufficient information for disease diagnosis, especially early detection and prognosis monitoring of tumors.