Toward Microfluidic Label-Free Isolation and Enumeration of Circulating Tumor Cells from Blood Samples

The isolation, analysis, and enumeration of circulating tumor cells (CTCs) from cancer patient blood samples are a paradigm shift for cancer patient diagnosis, prognosis, and treatment monitoring. Most methods used to isolate and enumerate these target cells rely on the expression of cell surface markers, which varies between patients, cancer types, tumors, and stages. Here, we propose a label-free high-throughput platform to isolate, enumerate, and size CTCs on two coupled microfluidic devices. Cancer cells were purified through a Vortex chip and subsequently flowed in-line to an impedance chip, where a pair of electrodes measured fluctuations of an applied electric field generated by cells passing through. A proof-of-concept of the coupling of those two devices was demonstrated with beads and cells. First, the impedance chip was tested as a stand-alone device: (1) with beads (mean counting error of 1.0%, sizing information clearly separated three clusters for 8, 15, and 20 um beads, respectively) as well as (2) with cancer cells (mean counting error of 3.5%). Second, the combined setup was tested with beads, then with cells in phosphate-buffered saline, and finally with cancer cells spiked in healthy blood. Experiments demonstrated that the Vortex HT chip enriched the cancer cells, which then could be counted and differentiated from smaller blood cells by the impedance chip based on size information. Further discrimination was shown with dual high-frequency measurements using electric opacity, highlighting the potential application of this combined setup for a fully integrated label-free isolation and enumeration of CTCs from cancer patient samples. © 2019 International Society for Advancement of Cytometry.