title: Characterization and resolution of evaporation-mediated osmolality shifts that constrain microfluidic cell culture in poly(dimethylsiloxane) devices.
abstract: Evaporation is a critical problem when handling submicroliter volumes of fluids. This paper characterizes this problem as it applies to microfluidic cell culture in poly(dimethylsiloxane) (PDMS) devices and provides a practical solution. Evaporation-mediated osmolality shifts through PDMS membranes with varying thicknesses (10, 1, 0.2, or 0.1 mm) were measured over 96 h. Even in humidified cell culture incubators, evaporation through PDMS and associated shifts in the osmolality of culture media was significant and prevented mouse embryo and human endothelial cell growth and development. A simple diffusion model, where the measured diffusion coefficient for PDMS matches reported values of approximately 10-9 m2/s, accounts for these evaporation and osmolality shifts. To overcome this problem, a PDMS-parylene-PDMS hybrid membrane was developed that greatly suppresses evaporation and osmolality shifts, yet possesses thinness and the flexibility necessary to interface with deformation-based microfluidic actuation systems, maintains the clarity for optical microscopy, and enables the successful development of single-cell mouse embryos into blastocysts under static conditions and culture of human endothelial cells under dynamic recirculation of submicroliter volumes of media. These insights and methods demonstrated specifically for embryo and endothelial cell studies will be generally useful for understanding and overcoming evaporation-associated effects in microfluidic cell cultures.
authors.affiliation: Department of Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Yun Seok
authors.initials: YS
authors.lastname: Heo
authors.forename: Lourdes M
authors.initials: LM
authors.lastname: Cabrera
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Song
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Futai
authors.forename: Yi-Chung
authors.initials: YC
authors.lastname: Tung
authors.forename: Gary D
authors.initials: GD
authors.lastname: Smith
authors.forename: Shuichi
authors.initials: S
authors.lastname: Takayama
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques / Q000295:instrumentation / Q000379:methods*; D003584:Cytological Techniques; D004058:Diffusion; D004129:Dimethylpolysiloxanes; D004622:Embryo, Mammalian; D042783:Endothelial Cells; D006801:Humans; D008567:Membranes, Artificial; D051379:Mice; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods*
chemical_list: D004129:Dimethylpolysiloxanes; D008567:Membranes, Artificial