Integrated Viscoelastic Microfluidics for Label-Free Separation and Concentration of Circulating Tumor Cells.

Developing advanced instrumentation systems for the automated, precise isolation of target circulating tumor cells (CTCs) from blood, followed by molecular marker analysis, stands as a pivotal trend in the field of liquid biopsy. However, current isolation technologies typically rely on subsequent centrifugation steps to enrich CTC samples for downstream assays, such as single-cell western blotting (scWB), creating challenges for developing integrated systems. Here, we present an integrated viscoelastic microfluidic system (IVEM) that leverages viscoelastic fluids to automatically separate and concentrate CTCs. The IVEM includes a CTC separation module (CSM) for high-purity isolation and a CTC concentration module (CCM) to remove excess cell suspension. To clarify the working mechanism, particle migration behavior is systematically analyzed through theoretical modeling and numerical simulations and validated by polystyrene (PS) particle experiments. The performance of the IVEM is evaluated through separation experiments using blood samples spiked with MCF-7 cells. The processing throughput, purity, recovery rate, and concentration factor of MCF-7 cells reach 1.82 mL·h-1, 82.13 ± 2.87, 81.30 ± 4.72, and 4.26 ± 0.92%, respectively. The IVEM enables label-free, continuous on-chip enrichment of separated CTCs without additional off-chip processing. This integration facilitates future incorporation of other functional modules, such as high performance single-cell capture, into liquid biopsy systems, thereby further enhancing the clinical applicability of technologies such as scWB.