Highly sensitive enumeration of circulating tumor cells in lung cancer patients using a size-based filtration microfluidic chip

• We developed a simple, low-cost and efficient size-based CTC isolation microchip.
• The chip used an array of filtration channels to isolate the larger CTCs from blood.
• The capability of the chip was investigated by isolating CTCs from spiked blood.
• The chip showed a highly efficient isolation of CTCs from whole blood.
• The chip was clinically validated by isolating CTCs from 59 lung cancer patients.

Circulating tumor cells (CTCs) in the peripheral blood could serve as a surrogate marker for the diagnosis of cancer metastasis and for therapeutic evaluation. However, the separation and characterization of CTCs is technically challenging owing to the extremely low number of CTCs present. Here we developed a size-based and high-throughput microfluidic chip, which exploits filtration microchannels to isolate the relatively larger CTCs from the rest of the blood constituents. High isolation efficiency of our microfluidic chip was demonstrated with three lung cancer cell lines spiked in blood samples at an optimal flow rate of 0.4 mL/h. The average recovery rates of 96%, 95% and 92% were obtained for A549, SK-MES-1, and H446, respectively. To clinically validate the chip, we also employed it to isolate CTCs from 59 lung cancer patients. CTCs were detected in 96.7% of patients with the mean number of 18.6 cells/mL, which was significantly higher than normal controls (P<0.05). The work here indicates that the size-based microfluidic platform with the advantage of capturing tumor cells without reliance on cell surface expression markers can provide a novel, inexpensive and effective tool for CTC detection and evaluation of cancer status.