Selection of DNA aptamer recognizing CD44 for high-efficiency capture of circulating tumor cells

Cancer stem cells play critical roles in cancer progression, cancer invasion and metastasis, and cancer recurrence. CD44 is known as a specific surface marker of cancer stem cells, which has been well-studied in cancer invasion and metastasis. Herein, we successfully selected the DNA aptamers for recognizing CD44+ cells using Cell-SELEX strategy, in which the engineered CD44 overexpression cells were used as target cells for selection. The optimized aptamer candidate C24S showed high binding affinity with the Kd value of 14.54 nM and good specificity. Then, the aptamer C24S was employed to prepare the functional aptamer-magnetic nanoparticles (C24S-MNPs) for CTC capture. To investigate the capture efficiency and sensitivity of C24S-MNPs, series of cell capture tests were performed using artificial samples with 10–200 of HeLa cells spiked into 1 mL PBS or PBMCs isolated from 1 mL peripheral blood, obtaining an efficiency of 95% and 90%, respectively. More importantly, we finally explored the facility of C24S-MNPs for CTC detection in blood samples from clinical cancer patients, indicating a potential and feasible strategy for cancer diagnostic technology in clinical applications.