Biobarcode and sequence-responsive DNA nanocapsules for label-free and sensitive electrochemical detection of circulating tumor cells

Monitoring trace circulating tumor cells (CTCs) in whole blood is important for early diagnosis and treatment of cancers. Whereas, it remains a major difficulty for detecting CTCs because of their extremely low contents in blood. Herein, by coupling biobarcode amplification method with sequence-responsive and enzyme-embedded DNA nanocapsules , we report a highly sensitive, label-free and specific electrochemical sensing assay to detect CTCs in blood. The target CTCs are selectively isolated from sample solutions by aptamer-conjugated magnetic beads and biobarcode DNA-functionalized polystyrene beads. Subsequent release of the biobarcode DNA can trigger the liberation of lots of enzymes from the nanocapsules, further leading to drastically enhanced catalytic current on the sensor electrode for detecting CTCs at the detection limit of 8 cell mL −1 in a non-label approach. Moreover, whole blood-spiked target CTCs can also be detected by the developed strategy, offering it the great promise for the monitoring of different rare CTCs in complex samples for various biomedical applications .