An electrochemiluminescent aptasensor for amplified detection of exosomes from breast tumor cells (MCF-7 cells) based on G-quadruplex/hemin DNAzymes.

Exosomes are non-invasive biomarkers for cancer diagnosis. Herein, we describe an electrochemiluminescent (ECL) aptasensor for the detection of exosomes from breast tumor cells. Mercaptopropionic acid (MPA)-modified Eu³⁺-doped CdS nanocrystals (MPA-CdS:Eu NCs) and H₂O₂ were used as ECL emitters and coreactant, respectively. The exosomes are recognized and captured by the CD63 aptamer, and then form a G-quadruplex/hemin DNAzyme, which efficiently catalyzes the decomposition of H₂O₂, resulting in the decreased ECL signal of MPA-CdS:Eu NCs. The exosomes from breast tumor cells (MCF-7 cells) can be detected in the range of 3.4 × 10⁵ to 1.7 × 10⁸ particles per mL. The limit of detection (LOD) was estimated to be 7.41 × 10⁴ particles per mL at a signal-to-noise ratio of 3. The aptasensor has been successfully used to detect exosomes in the serum.