Circulating tumor cells (CTCs) are tumor cells that are shed from cancerous tumors into the circulatory systems. CTCs are present in early-stage cancers and are reported to relate to disease prognosis. In recent years, CTCs have drawn increasing attention in both academic and industrial research, as they offer opportunities for the early detection, monitoring, treatment evaluation of cancer and its metastasis 1.
CTCs are challenging to capture, isolate and characterize in nature. First, CTCs are extremely rare in patients’ blood samples. One CTC usually exists among a background of millions of blood cells. Furthermore, CTCs are highly heterogeneous in physical characteristics and biological properties. No separation technology which is based on a single capture mechanism can produce pure and representative CTC subpopulations. In the traditional liquid biopsy, CTCs are isolated either by immunoaffinity strategies or by biophysical features differentiation. However, existing macro-scale isolation systems suffer important drawbacks, such as low capture efficiency, incomplete automation and low viability of captured CTCs 2. As a promising alternative, microfluidic technologies have gained tremendous interest in the field. Microfluidic technologies create devices that are at or smaller than the cellular length scale and enable accurate capturing and manipulation at single cell level. These technologies also offer precise control of fluid flow, which can greatly facilitate affinity reactions and physical separation. Moreover, on a microfluidic chip, CTC capturing and next-step analysis can be integrated to minimize intermediate sample handling and shorten the processing time. Above all, microfluidic approaches allow gentle isolation of live cells and thus enable many downstream analyses that rely on captured live CTCs 3. (more…)