The system consists of a two-phase laminar flow following droplet formation and is thermally controlled to allow for interphase diffusion of water into the organic phase. We developed a mathematical model to show that preconcentration of cells is possible by dehydrating picoliter aqueous droplets in an organic phase in a microfluidic channel by reducing the exposure time to CPAs, eliminating the multistep CPA loading-diluting procedures, and avoiding the mechanical and osmotic stresses caused by large concentration differences. An alternative approach for safer cryopreservation is to modify the protocols to control the loading and concentration of CPAs in and around the cell prior to freezing. Vitrification by rapid cooling requires the employment of carbohydrate based cryoprotectant agents (CPAs) to accommodate for the ultrafast cooling rates and to prevent intra- and extra-cellular crystallization by increasing the glass transition temperature at the cost of toxicity.
Freezing at cryo temperatures by slow cooling causes cell injury due to ice formation and cell dehydration. Cells contain about 80% cytoplasmic water by volume, which requires cooling rates faster than 1,000,000 C/s to transform into glass, and respond atypically to osmotic fluctuations. Cryopreservation by conventional slow freezing and by vitrification below freezing temperatures are the most effective biopreservation methods compared to in vitro culture at physiological temperatures and hypothermic storage at low temperatures above the freezing point. Safe preservation of mammalian cells for long term is essential for medical and pharmaceutical industries.