High-throughput and simultaneous inertial separation of tumor cells and clusters from malignant effusions using spiral-contraction-expansion channels

Tumor cell clusters are regarded as critical factors in cancer pathophysiology, and increasing evidence of their higher treatment resistance and metastasis compared to single tumor cells has been obtained. However, existing cell separation methods that are designed for single tumor cells cannot be used to simultaneously purify tumor cell clusters. To address this problem, we demonstrated a microfluidic approach for the high-throughput, continuous-flow ternary separation of single tumor cells, tumor cell clusters, and WBCs from clinical pleural or abdominal effusions by coupling slanted spiral channels and periodic contraction-expansion arrays. We first systematically explored the influence of particle size and flow rate on particle focusing. The separation performance indicated that 94.0% of WBCs were removed and more than 97% of MDA-MB-231 tumor cells were recovered at a high flow rate of 3500 µL/min. Moreover, more than 90% of tumor cell clusters were effectively preserved after separation. Finally, we successfully applied our device for the ternary separation of single tumor cells, tumor cell clusters, and WBCs from different malignant effusions collected from patients with metastatic cancer. Thus, our spiral-contraction-expansion device has potential as a sample pretreatment tool for the cytological diagnosis of malignant effusions.