Homogenous Electrochemical Method for Ultrasensitive Detection of Tumor Cells Designed by Introduction of Poly(A) Tails onto Cell Membranes.

Rapid and efficient detection of tumor cells is one of the central challenges for modern analytical technology. In this paper, we report a polyadenine (poly(A)) tail-based strategy for ultrasensitive detection of tumor cells in aqueous solution with an electrochemical technique. Specifically, tumor cell-specific EpCAM aptamers without any modification can tightly bind on cell membranes and facilitate the subsequent introduction of multiple poly(A) tails via programmable terminal deoxynucleotidyl transferase (TdT)-mediated elongation. Meanwhile, since tumor cells bearing poly(A) tails can be easily adsorbed onto the surface of gold electrodes through a strong interaction between adenosines and gold, a highly amplified electrochemical signal can be obtained. Thus, by virtue of poly(A) tails, the proposed method allows the detection of as low as 3 cells mL. Compared with the previously reported methods for tumor cells detection, this poly(A)-based homogeneous electrochemical method needs just one enzyme and one aptamer without any modification and avoids the complex and time-consuming modification process of the working electrode, which holds great potential application in the future.