Poly(ethylene oxide) Concentration Gradient-Based Microfluidic Isolation of Circulating Tumor Cells

Circulating tumor cells (CTCs) have emerged as promising circulating biomarkers for non-invasive cancer diagnosis and management. Isolation and detection of CTCs in clinical samples are challenging due to the extreme rarity and high heterogeneity of CTCs. Here, we describe a poly(ethylene oxide) (PEO) concentration gradient-based microfluidic method for rapid, label-free, highly efficient isolation of CTCs directly from whole blood samples. Stable concentration gradients of PEO were formed within the microchannel by co-injecting the side fluid (blood sample spiked with 0.025% PEO) and center fluid (0.075% PEO solution). The competition between the elastic lift force and the inertial lift force enabled size-based separation of large CTCs and small blood cells based on their distinct migration patterns. The microfluidic device could process 1 mL of blood sample in 30 min, with a separation efficiency of >90% and an enrichment ratio of >700 for tumor cells. The isolated CTCs from blood samples were enumerated by immunofluorescence staining, allowing for discrimination of breast cancer patients from healthy donors with an accuracy of 84.2%. The concentration gradient-based microfluidic separation provides a powerful tool for label-free isolation of CTCs for a wide range of clinical applications.

Automated summary

In this study, a microfluidic method based on poly(ethylene oxide) (PEO) concentration gradient was developed for rapid, label-free, and highly efficient isolation of circulating tumor cells (CTCs) from whole blood samples. By co-injecting blood sample spiked with 0.025% PEO as the side fluid and 0.075% PEO solution as the center fluid, stable concentration gradients of PEO were formed within the microchannel. The competition between elastic lift force and inertial lift force enabled size-based separation of CTCs and blood cells, with a processing capacity of 1 mL of blood sample in 30 min, separation efficiency >90%, and enrichment ratio >700 for tumor cells. Immunofluorescence staining of the isolated CTCs allowed for accurate discrimination of breast cancer patients from healthy donors with an accuracy of 84.2%. The concentration gradient-based microfluidic separation provides a powerful tool for label-free isolation of CTCs for various clinical applications.