A one-step electrochemical strategy for rapid exosome detection using Cu²⁺-coordinated DNA nanoparticles

Stimulus-responsive nucleic acid nanomaterials are attractive for label-free electrochemical biosensing because their programmable structures enable target-triggered signal generation in homogeneous systems. Herein, we report a one-step electrochemical strategy for rapid and highly sensitive detection of ovarian cancer (OC)-derived exosomes based on target-responsive Cu²⁺-coordinated DNA nanoparticles (Cu²⁺@DNA-NPs). In this design, aptamer sequences are incorporated into Cu²⁺@DNA-NPs to endow the nanostructures with target-recognition capability, while the coordinated Cu²⁺ ions serve directly as intrinsic electrochemical reporters. Upon aptamer-mediated recognition of exosomal surface markers, the DNA structure switching may expose the initiator strands that trigger a localized hybridization chain reaction (HCR) within the nanoparticles, thereby promoting the nanoparticle disassembly and subsequent Cu²⁺ release for amplified electrochemical signal generation. Notably, this strategy enables label-free signal amplification in a homogeneous solution-phase format without electrode modification or additional redox labels. Moreover, the fabricated biosensor based on this strategy achieves rapid analysis within approximately 35 min, together with a low detection limit of 9 particles/mL, good selectivity against non-target exosomes and other interferents, as well as satisfactory stability and reproducibility. The biosensor has been further validated by using clinical samples, where it can clearly discriminate patients from healthy controls. Overall, this work establishes a rational and efficient electrochemical sensing strategy for rapid exosome analysis and the strategy-based biosensor may have potential utility in early OC diagnosis and metastasis monitoring.