RESUMEN
This study considers the use of a two-stream microfluidic device for extraction of dimethyl sulphoxide (DMSO) from a cryopreserved cell suspension. The DMSO diffuses from a cell suspension stream into a neighboring wash stream flowing in parallel. The model of Fleming et al.[14] is employed to determine and discuss optimal geometry and operating conditions for a case requiring removal of 95% DMSO from suspension streams with volumetric flow rates up to 2.5 ml/min. The effects of Peclet number, flow rate fraction, and cell volume fraction are analyzed, and expansion of the analysis to other applications is discussed.
RESUMEN
Cells are routinely cryopreserved in dimethyl sulfoxide (DMSO), a cryoprotective agent, for medical applications. Infusion of a DMSO-laden cell suspension results in adverse patient reactions, but current DMSO extraction processes result in significant cell losses. A diffusion-based numerical model was employed to characterize DMSO extraction in fully developed channel flow containing a wash stream flowing parallel to a DMSO-laden cell suspension. DMSO was allowed to diffuse across cell membranes as well as across the channel depth. A variety of cases were considered with the ultimate goal of characterizing the optimal geometry and flow conditions to process clinical volumes of cell suspension in a reasonable time (2-3 ml/min). The results were dependent on four dimensionless parameters: depth fraction of the DMSO-laden stream, Peclet number, cell volume fraction in the DMSO-laden stream, and cell membrane permeability parameter. Smaller depth fractions led to faster DMSO extraction but channel widths that were not practical. Higher Peclet numbers led to longer channels but smaller widths. For the Peclet values and channel depths considered (>or=500 microm) and appropriate permeability values, diffusion across cell membranes was significantly faster than diffusion across the channel depth. Cell volume fraction influenced the cross-stream diffusion of DMSO by limiting the fluid volume fraction available in the contaminant stream but did not play a significant role in channel geometry or operating requirements. The model was validated against preliminary experiments in which DMSO was extracted from suspensions of B-lymphoblast cells. The model results suggest that a channel device with practical dimensions can remove a sufficient level of contaminant within a mesoscale volume of cells in the required time.