Hybrid microfluidic sorting of rare cells based on high throughput inertial focusing and high accuracy acoustic manipulation.

The ability to isolate rare circulating tumor cells (CTCs) from blood samples is essential to perform liquid biopsy as a routine diagnostic and prognostic test. Both label-free and surface biomarker-based cell sorting technologies have been developed to address the demand in high-integrity isolation of rare CTCs for cancer research. Label-free cell sorting mainly relies on the size difference between CTCs and blood cells; thus, it lacks sufficient sorting specificity. Surface biomarker-based cell sorting is highly specific; however, it requires expensive, labor-intensive, and time-consuming labeling due to the use of multiple sets of surface biomarkers. Because of the complex nature and high heterogeneity of tumorigenesis, it is difficult to rely on a single sorting process for high-integrity rare cell isolation. In this study, for the first time, we present a hybrid microfluidic cell sorting method combining high throughput size-dependent inertial focusing for size-based pre-enrichment and high accuracy fluorescence activated acoustic sorting for single cell isolation. After one single hybrid sorting process, we have demonstrated at least 2500-fold purity enrichment of MCF-7 breast cancer cells spiked in diluted whole blood samples with cell viability maintained at 91 ± 1% (viability before sorting was 94 ± 2%). This developed hybrid microfluidic cell sorting technique provides a promising solution for rare cell isolation needed in a variety of biological research and clinical applications.