An electrochemical biosensor to detect exosomes based on their assembly with silver nanoparticles and multifunctional peptides.

Exosomes have been valuable biomarkers for disease diagnosis, however their low abundance still presents challenge for clinical application. In this paper, we report an electrochemical biosensor that enables sensitive and specific detection of exosomes without the requirement of pretreatment steps and signal amplification. In this study, the designed multifunctional peptides are firstly conjugate with silver nanoparticles (AgNPs) through sulfhydryl groups to form Pep-AgNPs, and subsequently combine with exosomes via the targeting sequence. Under acidic conditions, protonation of the peptide termini induces electrostatic interactions with exosomal surfaces, driving the assembly of Pep-AgNPs@Exo-clusters. The loaded AgNPs then generate high electrochemical signals, while the enrichment of exosomes and AgNPs may further enhance detection sensitivity, affording a wide linear range (102-107 particles/μL) and an ultralow detection limit (44 particles/μL). The proposed biosensor has been successfully implemented in clinical serum samples from breast cancer patients and healthy individuals, demonstrating its potential for early diagnosis of the cancer.