High-yield purification of rare blood cells by immunospecific size enhancement in an inertial microfluidic device

Abstract

Circulating rare cells in blood provide valuable information and their separation can open opportuni-ties for biological studies. Separation of circulating tumor cells (CTCs) in specific can be used as a non-invasive liquid biopsy and biomarker for cancer diagnosis and screening purposes. CTCs are generally larger than white blood cells (WBCs) and many size-based separation methods utilizing inertial microfluidics for high throughput separation have been developed in recent years. However, due to the overlap in size distribu-tions between WBCs and CTCs, it has been difficult to separate with both high recovery rate and purity. In this study, to overcome the limitation of size-based inertial separation of CTCs from WBCs, immunospecific size enhancement was applied to eliminate that size overlap. To demonstrate improved separation, mi-crobeads are attached to CTCs by antigen-antibody binding to enhance their sizes, and then separated from WBCs in an inertial microfluidic separating device that consists of a series of contraction-expansion arrays (CEA). In addition, the dimensions of CEA device were systematically varied for optimal separation performance and computational fluid dynamics simulations were performed to characterize the secondary flows in the device. Breast cancer and monocyte cancer cell lines were chosen to model CTCs and WBCs inertial migration in the optimized device, respectively, and then breast cancer cells were labeled with beads to compare the separation performance. The device separates unlabeled CTCs from WBCs with 74% recovery rate and 76% WBC rejection ratio at 0.88 ml/h. However, increased recovery rate of 97.6% and 95% WBC rejection ratio at 0.88 ml/h was demonstrated by labeling the CTCs with 5 μm beads. With increased recovery rate and purity provided by increased WBC rejection ratio, inertial separation of bead-labeled CTCs not only has the potential to improve the clinical diagnostic, prognostic and screening results, but also to ...