Method of purifying tumor cells using shear stress

A method for purifying a fluid sample comprising

• contacting viable cancerous cells, viable normal cells and extracellular calcium with a micro fluidic device comprising:
• (a) a conduit configured to contain the fluid sample;
• and
• (b) a motorized pump operably coupled to the conduit, the motorized pump configured to pass the fluid sample through the conduit at a flow rate,
• wherein the conduit and the motorized pump are configured to apply an initial pulse of fluid shear stress to the fluid sample in vitro, said initial pulse of fluid shear stress sufficient to induce a fluid shear stress resistance in the viable cancerous cells such that the magnitude of shear stress required to kill the viable cancerous cells is greater than the magnitude of shear stress required to kill the viable normal cells;
• and
• wherein the conduit and the motorized pump are configured to subsequently apply one or more additional pulses of fluid shear stress to the fluid sample in vitro, said fluid shear stress sufficient to selectively kill the viable normal cells relative to the viable cancerous cells such that a ratio of the viable cancerous cells to the viable normal cells is increased;
• applying an initial pulse of fluid shear stress to the fluid sample, wherein the initial pulse of fluid shear stress induces a fluid shear stress resistance in the viable cancerous cells such that the magnitude of shear stress required to kill the viable cancerous cells is greater than the magnitude of shear stress required to kill the viable normal cells;
• and
• subsequently applying one or more additional pulses of fluid shear stress to the fluid sample comprising the fluid shear stress-resistant viable cancerous cells, said fluid shear stress sufficient to selectively kill the viable normal cells relative to the viable cancerous cells, whereby the ratio of viable cancerous cells to viable normal cells in the preparation is increased.