Electrochemical aptasensor based on multidirectional hybridization chain reaction for detection of tumorous exosomes

Abstract

Exosomes-based liquid biopsy is an anticipated application, in which high sensitivity detection with good selectivity is an important determinant of assay quality. Herein, we propose an electrochemical aptasensor for the selective and sensitive detection of tumorous exosomes. It is based on multidirectional hybridization chain reaction (mHCR) for signal amplification. The aptamers are first immobilized on gold electrode surface to capture exosomes by binding to the exosomal membrane proteins. After target capture, cholesterol-modified H shape-like DNA unit 1 (cH1) is capable of plunging cholesterol into the exosomal lipid bilayer and anchoring on the exosomal membrane. The mHCR is therefore carried out at cH1 in the presence of H shape-like DNA unit 1 (H1) and H shape-like DNA unit 2 (H2) to form a large DNA nanostructure, which enables to recruit multiple signal molecules for electrochemical signal amplification. Under the optimal conditions, the electrochemical aptasensor exhibits high sensitivity with a low limit of detection (LOD) of 285 exosomes/μL. In addition, it shows selective discrimination between tumorous and non-tumorous exosomes from cells and serum samples. Overall, the proposed aptasensor shows potential value for exosomes detection in the early diagnosis and screening of cancers.