An electrochemical aptasensor for exosomes based on strand displacement amplification and hybridization chain reaction amplification

Exosomes are lipid bilayer vesicles, relating to the happening and progress of cancer. However, exploring reliable, convenient and sensitive exosomes detection methods in early cancer diagnosis is still challenging. Here, an electrochemical aptasensor based on both signal amplifications of strand displacement amplification (SDA) and hybridization chain reaction (HCR) was developed to sensitively detect tumor exosomes. Firstly, exosomes were recognized by CD63 aptamer, and converted into DNA concentration by chain replacement reaction and magnetic separation. A produced DNA fragment (P) was obtained by SDA，then P was captured at the modified gold electrode and amplified using HCR. Abundant horseradish peroxidase (HRP) attached to DNA concatemers and catalyzed the oxidation of o-phenylenediamine (OPD). The reduction current of 2,3-diaminopenazine (DAP) was measured and the exosomes were quantized. Under the optimal conditions, the DPV response showed a great linear relationship with exosomes concentration range of 44 ∼ 8.8 × 10⁶ particle/μL. The limit of detection was 18 particle/μL. Experimental results show that this is an alternative method to detect exosomes and other tumor markers.