Circulating tumor cells (CTCs) have been utilized in the diagnosis and prognosis of tumor. However, the CTC concentration is extremely low to be detected in peripheral blood. Many existing methods suffer from either expensive labeling or complex operation. In this study, we constructed a label-and enzyme-free and sensitive method to detect the breast cancer CTCs. First of all, a probe containing a breast cancer cell-specific aptamer and a complementary single-stranded DNA (trigger DNA P1) were designed. When the target cells are present, the aptamer binds to the CTCs and releases P1 which triggers the strand displacement amplification. This process generates three-way junction structure DNA, the specific translocation signals of which are identified by nanopore assay. The detection limit of tumor cells is 5 in the current experimental setup and can be further reduced. Furthermore, the method is demonstrated in a clinical sample test with high recovery rate and accuracy. Our results suggest that this method could be applied to early diagnosis of metastatic recurrence and prognosis determination.

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