Target induced framework nucleic acid nanomachine with doxorubicin-spherical nucleic acid tags for electrochemical determination of human telomerase activity

A stable and enzyme-free method is described for highly sensitive determination of telomerase activity. It is based on the use of a framework nucleic acid (FNA) nanomachine and doxorubicin-spherical nucleic acid (DSNA) tags. Upon incubation with telomerase, the primer-tetrahedron becomes elongated to form the handed swing arm. The extended swing arm autonomously moves along the predefined track consisting of entropy-tetrahedron by consecutive strand displacement under the aid of fuel-tetrahedron. As a result, many (entropy-tetrahedron)-(fuel-tetrahedron) complexes are assembled for combining the DSNA tags. This results in an amplified electrochemical signal, typically measured at around −0.63 V (Ag/AgCl). The use of an enzyme-free FNA nanomachine and of DSNA tags warrants outstandingly high stability and sensitivity. The method shows a broad dynamic correlation of telomerase activity in cell extracts. The analytical range extends from 10 to 1.0 × 10 4 HeLa cells mL −1 with a lower detection limit of 2 cells mL −1 . The differences in telomerase activity between different cancer cells can be easily evaluated. The method was further verified by quantifying telomerase activity of cancer cells in accumulated normal cells. Therefore, the sensing method has great potential for clinical application. Graphical abstract Schematic representation of the electrochemical biosensor based on target induced framework nucleic acid nanomachine with doxorubicin-spherical nucleic acids (DSNA) tags, which can be used to the determination of telomerase activity in accumulated normal cells. dNTP: Deoxynucleotide triphosphates; FT: Fuel-tetrahedron.