Mechanical Low-Pass Filtering of Cells for Detection of Circulating Tumor Cells in Whole Blood

The detection of circulating tumor cells (CTCs) from liquid biopsies using microfluidic devices is attracting a considerable amount of attention as a new, less-invasive cancer diagnostic and prognostic method. One of the drawbacks of the existing antibody-based detection systems is the false negatives for epithelial cell adhesion molecule detection of CTCs. Here we report a mechanical low-pass filtering technique based on a microfluidic constriction and electrical current sensing system for the novel CTC detection in whole blood without any specific antigen-antibody interaction or biochemical modification of the cell surface. The mechanical response of model cells of CTCs, such as HeLa, A549, and MDA-MB-231 cells, clearly demonstrated different behaviors from that of Jurkat cells, a human T-lymphocyte cell line, when they passed through the 6-μm wide constriction channel. A 6-μm wide constriction channel was determined as the optimum size to identify CTCs in whole blood with an accuracy greater than 95% in tens of milliseconds. The mechanical filtering of cells at a single cell level was achieved from whole blood without any pretreatment (e.g., dilution of lysing) and prelabeling (e.g., fluorophores or antibodies).