Rapid and cost-efficient enumeration of rare cancer cells from whole blood by low-loss centrifugo-magnetophoretic purification under stopped-flow conditions.

We present a substantially improved design and functionality of a centrifugo-magnetophoretic platform which integrates direct immunoseparation and cost-efficient, bright-field detection of cancer cells in whole blood. All liquid handling takes place in a disposable cartridge with geometry akin to a conventional compact disc (CD). The instrumentation required to process such a "lab-on-a-disc" cartridge can be as simple and cost-efficient as the rotor on a common optical disc drive. In a first step, target cells in a blood sample are specifically bound to paramagnetic microbeads. The sample is then placed into the disc cartridge and spun. In the second step, magnetically tagged target cells are separated by a co-rotating, essentially lateral magnetic field from the background population of abundant blood cells, and also from unbound magnetic beads. A stream of target cells centrifugally sediments through a stagnant liquid phase into a designated detection chamber. The continuous, multiforce immunoseparation proceeds very gently, i.e. the mechanical and hydrodynamic stress to the target cells is minimized to mitigate the risk of cell loss by collective entrapment in the background cells or vigorous snapping against a wall. We successfully demonstrate the extraction of MCF7 cancer cells at concentrations as low as 1 target cell per μl from a background of whole blood, with capture efficiencies of up to 88%. Its short time-to-answer is a notable characteristic of this system, with 10% of target cells collected in the first minute after their loading to the system and the remainder captured within the following 10 min. All the above-mentioned factors synergetically combine to leverage the development of a prospective point-of-care device for CTC detection.