Capturing rare cells from blood using a packed bed of custom-synthesized chitosan microparticles

We describe batch generation of uniform multifunctional chitosan microparticles for isolation of rare cells, such as circulating tumor cells (CTCs), from a sample of whole blood. The chitosan microparticles were produced in large numbers using a simple and inexpensive microtubing arrangement. The particles were functionalized through encapsulation of carbon black, to control autofluorescence, and surface attachment of streptavidin, to enable interactions with biotinylated antibodies. These large custom modified microparticles (≈164 μm diameter) were then packed into a microfluidic channel to demonstrate their utility in rare cell capture. Blood spiked with breast cancer (MCF-7) cells was first treated with a biotinylated antibody (anti-EpCAM, which is selective for cancer cells like MCF-7) and then pumped through the device. In the process, the cancer cells were selectively bound to the microparticles through non-covalent streptavidin-biotin interactions. The number density of captured cells was determined by fluorescence microscopy at physiologically relevant levels. Selective capture of the MCF-7 cells was characterized, and compared favorably with previous approaches. The overall approach using custom synthesized microparticles is versatile, and can allow researchers more flexibility for rare cell capture through simpler and cheaper methods than are currently employed.