Dual Recognition Strategy-Based Ratiometric Electrochemical Assay for Ultrasensitive and Accurate Detection of Specific Circulating Tumor Cells

Sensitive, specific, and accurate detection of circulating tumor cells (CTCs) is of great importance in the diagnosis and prognosis of cancer. Herein, an ultrasensitive ratiometric electrochemical biosensor was designed with a dual recognition strategy for highly specific and accurate detection of circulating MCF-7 human breast cancer cells based on gold film-modified porous organic cages loaded with ferrocene (Au/Fc@POCs) as the substrate and methylene blue-encapsulated covalent organic frameworks (MB@COFs) as the label material, producing two independent electrochemical signals from the Fc and MB probes, respectively. As the concentration of MCF-7 cells increases, the electrochemical signal of MB enhances significantly while the oxidation signal of Fc decreases remarkably. Under optimal experimental conditions, the ratios (