Catalytic hairpin assembly-triggered DNA walker for electrochemical sensing of tumor exosomes sensitized with Ag@C core-shell nanocomposites.

The detection of a small number of exosomes provides the possibility for early cancer diagnosis and prognosis. Here, a multi-signal amplified electrochemical sensing platform was explored for the ultrasensitive detection of tumor exosomes relying on catalytic hairpin assembly-triggered DNA walker, entropy beacon-based DNA assembly and Ag@C core-shell nanocomposites. In this work, the utilization of Ag@C nanocomposites as electrode interface effectively enhanced functional active sites and electron transfer capability. By designing a target-assisted entropy beacon-based DNA assembly, single exosome initiated the release of multiple special DNA sequences, which could be separated conveniently by magnet and then hybridize with the blocking DNA to liberate swing arm. DNA walker was activated with the assistance of catalytic hairpin assembly, introducing extensive electroactive methylene blue (MB) to electrode surface. Thus, the detection of exosomes was transferred into the measurement of the MB current, with a good liner range from 100 to 75 000 particles/μL. Furthermore, this constructed sensing system displayed acceptable reproducibility, long-term stability, favorable selectivity, and highlighting application potential in real samples.