Colorimetric assay of rare disseminated tumor cells in real sample by aptamer-induced rolling circle amplification on cell surface

The identification of tumor cells disseminating in body fluids plays a critical role in the accurate diagnosis of cancer. Herein, a simple and pragmatic colorimetric strategy has been developed for ultrasensitive detection of tumor cells based on aptamer-induced rolling circle amplification (RCA) on cell surface. An Epithelial Cell Adhesion Molecule (EpCAM)-targeted aptamer was selected as recognition agent to specifically recognize and bind with tumor cells. Following, the aptamer-induced RCA performed in situ, presenting numerous G-quadruplexes sequences on the cell surface. G-quadruplex/hemin DNAzyme then formed and catalyzed colorimetric reaction for tumor cells detection. The proposed aptamer-induced RCA strategy displayed remarkable signal amplification performance and high specificity. The designed colorimetric assay could distinguish as low as 10 cancer cells in 10000 times of benign cells mixture, showing very high sensitivity and selectivity. Moreover, it has been successfully verified that the established strategy could directly identify tumor cells disseminated from various primary sites in multiple types of clinical body fluid samples. Thus this proposed strategy provided a simple, handy and powerful platform for ultrasensitive detection of tumor cells and had great potential for clinical application in convenient assay of rare disseminated tumor cells in body fluid samples for early cancer screening.