A numerical study on the loading of cryoprotectant cocktails-on-a-chip.Part Ⅱ: The cellular experience

摘要

We present a numerical investigation of the simultaneous loading of a cocktail of propanediol and dimethyl sulfoxide into human sperm cells inside of a Microchannel. The Microchannel simulated has one central upstream inlet for cells, two upstream sheath inlets with one of the cryoprotective agents, and two downstream sheath inlets with the other cryoprotective agent. Of primary interest is how the complicated viscosity and velocity profiles caused by the viscous and miscible fluids affects the cells, both in terms of strain rate and cryoprotective agent mass transport. Despite the characteristic time scale of the trans-membrane mass transport being small, at certain flow rates, the high Peclet number flow inside of the Microchannel limits the extracellular cryoprotectant concentration available to the cells. At low flow rates, the intracellular concentrations of both components will reach those of the perfectly mixed values. Increasing to moderate flow rates (near 1 μL/min), the intracellular concentration of the upstream cryoprotective agent will exceed the perfectly mixed value, "super-loading", while there is still appreciable loading of the downstream cryoprotectant. Increasing the flow rate towards 10 (μL/min, a large distribution of the upstream cryoprotectant is seen across the cells while minimal downstream cryoprotectant enters the cells. The utility of such a model to aid in the optimization of cryopreservation protocols for a range of cells and cryoprotective cocktails is discussed.