A fluorescent immunosensor for determination and imaging of circulating tumor cells based on a bifunctional DNA nanomachine

A fluorescent platform was developed for the determination and visualization of circulating tumor cells by a toehold-mediated bifunctional DNA nanomachine. In the presence of target tumor cells, the DNA nanomachine was activated. Multiple DNA products were formed, including dendritic DNA products and double-strand DNA products. Dendritic DNA products bound to their target cells for the visualization, while double-strand DNA products were released for the determination of tumor cells. At fluorescence excitation and emission wavelengths of 530 and 550 nm, this method could detect as low as 43 cells/mL (S/N = 3) with a linear range of 100 to 10,000 cells/mL. In clinical hydrothorax samples, this platform exhibited high reliability with a recovery of 93 to 116%. At the fluorescence excitation and emission wavelengths of 490 and 515 nm, the specificity and biocompatibility of this method were further verified by tumor cells imaging. Furthermore, the robustness of the toehold-mediated bifunctional DNA nanomachine was demonstrated by the specific gene mutation detection in single-cell analysis.