Influence of natural deep eutectic systems in water thermal behavior and their applications in cryopreservation

Natural deep eutectic systems (NADES), which have applications as solvents for both engineering and life sciences, are mainly composed of sugars, aminoacids or organic acids. In this work NADES composed by glucose, urea and proline (G:U:P in a molar ratio of 1:1:1) and proline and glucose (P:G 5:3) were prepared and added in different mass fractions to water. By differential scanning calorimetry it was verified as the crystallization tendency of water is modified even for low fraction of NADES added. This is also observed by polarized optical microscopy which allowed following the formation of crystals with different crystalline morphologies as bulk water. Calorimetric data also shown as the crystallization temperature decreases for all P:G mixtures and this shift is more accentuated for weight fraction of NADES higher than 0.5. Crystallization is totally suppressed for NADES fraction higher than 0.7. NADES/water mixtures cytotoxicity was evaluated in vitro, revealing that they are less toxic as compared with the commonly used cryoprotective additives as dimethyl sulfoxide (DMSO). Additionally, cell viability tests with cell lines cryopreserved using DMSO and both the prepared NADES showed comparable viability. This work combines thermophysical data on NADES and evaluates it's in vitro performance, providing cues for their use in cryopreservation applications.