In this configuration, only the small proportion of the sample in contact with the cold wall was initially undercooled to any significant degree. In metallurgy this mode of solidification is referred to as progressive or parallel solidification [26] and we shall refer to this as PS when considering ice formation. In order to develop protocols rapidly and efficiently for the cryopreservation of large volumes it is necessary to develop and validate a scale down method to emulate the process of ice formation

that occurs within a large volume in comparison to that within a standard cryovial. This approach allows multiple samples to be tested within the same run, and also the effects of thawing to be de-coupled from the freezing step which produces either PS or NS. We also designed a technique to reliably produce PS in small volumes, removing the compounding

factor of sample volume XL184 on the ice solidification process. In this study, we examined the viability and cell function of ELS (where we have extensive previous experience of post-cryopreservation functional assessment) [15], [16] and [17] following either PS or NS. In addition we determined, by CryoSEM, the structure of the ice crystal networks and the residual freeze concentrated matrix following water to ice phase transition by these two methods. The techniques for producing ELS have been described previously in detail [4]. HepG2 cells (human-derived hepatocyte cell-line) were grown in monolayer U0126 ic50 culture for 7 days and passaged at 80–90% confluence. Selleckchem Abiraterone Culture medium composed of alpha-MEM medium, supplemented with 50 U/ml penicillin, 50 μg/ml streptomycin (Invitrogen plc.), and 10% FCS (Hyclone Thermo Scientific). A suspension of 3.5 × 106 cells/ml in culture medium mixed 1:1 with 2% aqueous alginate solution (FMC bio-polymers), was passed through a jetcutter system (GeniaLab), resulting in spherical droplets with a diameter of 500–550 μm, which were polymerised by ejection

into a buffer with 0.204 M CaCl2. These (ELS) were grown in culture medium at a ratio of beads to medium of 1:32 in static culture (T175 flasks) in a 5% CO2 humidified incubator at 37 °C for 11 days, with medium changed every 2–3 days, where they proliferated to approximately 1 × 107 cells/ml. For typical PS in a true large volume experiment, a prototype of the cylindrical BAL cassette constructed out of polycarbonate and containing 2000 ml of a 10% glycerol in water (v/v) solution as an ELS thermal mimic was cooled on its side on a modified VIAFreeze controlled rate freezer (Asymptote, Cambridge, UK). Good thermal contact was achieved via a curved plate attached to the cassette (Fig. 2). To ensure good thermal contact between the cassette and the sample plate a film of low temperature silicone oil (Sigma, 85409) was applied to the sample plate.