Analysis of coupled water and dimethyl sulfoxide transport in algae

Summary form only. Cryopreservation of living cells requires the addition of a cryoprotective agent (CPA) to avoid injury during freezing and thawing. However, addition/removal of the CPA can induce damaging osmotic stresses transmembrane. Thus, optimal design of cryopreservation protocols requires quantitative understanding of water and CPA transport over the operating temperature range. A model is presented for fluid transport through a cell membrane as a function of water and permeable solute fluxes. The experimental procedure to determine key model parameters involves perfusion of spherical Chlorococcum texanum fresh-water algae cells with concentrated sucrose solution, followed by exposure to an equally concentrated CPA/sucrose solution. Interaction with the sucrose solution, to which the membrane is impermeable, causes an osmotic response reducing cell volume. The CPA/sucrose solution in turn partially reestablishes the cell volume as the CPA diffuses into the cell. Analysis of osmotic response to methanol CPA has been completed, and current research investigates permeability properties to dimethyl sulfoxide (DMSO), a more common CPA. Early results show that methanol diffuses through the algae membrane more than twice as quickly as DMSO, resulting in reduced osmotic stress