Poly(l-Ala-co-l-Lys) Exhibits Excellent Ice Recrystallization Inhibition Activity

Abstract

The control of ice recrystallization is very important in cryo-technological fields such as the food industry, biopharmaceuticals, and cell storage. Ice recrystallization inhibition (IRI) compounds are therefore designed to limit the growth of ice crystals, decrease the crystal size, and control the crystal shape. To improve the IRI activity of cryo-systems, various synthetic polymers such as biomimetic polypeptides from polar fish, facially amphiphilic polymers, polyampholytes, poly­(vinyl alcohol) derivatives, and block copolymers with hydrophilic–hydrophobic balance have been developed. Except for graphene oxide, poly­(vinyl alcohol) has thus far exhibited the best performance among these polymers. Herein, poly­(l-alanine-co-l-lysine) (PAK) was shown to exhibit a similar IRI activity to that of poly­(vinyl alcohol). Moreover, in contrast to the needle-shaped ice crystals generated by the aqueous PVA solution, the PAK solution was shown to generate cubic-to-spherical shaped ice crystals. Furthermore, neither poly­(l-alanine-co-l-aspartic acid) (PAD) nor poly­(ethylene glycol) (PEG) with a similar molecular weight provided any significant IRI activity. Examination by FTIR and circular dichroism spectroscopies indicated that the PAK forms α-helices, whereas the PAD forms random coils in water. Further, a dynamic ice shaping study suggested that PAK strongly interacts with ice crystals, whereas PAD and PEG only weakly interact. These results suggest that PAK is an important compound with superior IRI activity and that this activity is dependent upon the functional groups and secondary structure of the polypeptides.

Poly(l-alanine-co-l-lysine)-g-Trehalose as a Biomimetic Cryoprotectant for Stem Cells

“…The above data confirm that preincubation of PEG-PAK T significantly improves the cell recovery rate only when the concentrations of PEG-PAK T and trehalose are in a certain range. Recently, we reported PAK as an IRI-active polymer . The polymer was used for ice crystal control of ice cream.…”

Bioinspired Cryoprotectants Enabled by Binary Natural Deep Eutectic Solvents for Sustainable and Green Cryopreservation

“…Ice recrystallization is always a vexing problem in cryotechnological areas because it causes irreversible damage to cryopreserved cells or tissues . Hence, cryoprotectants showing the ability to limit the ice crystal growth, decrease the crystal size, and control the crystal shape are highly pursued nowadays . After evaluating the antifreezing capacity, the ice recrystallization inhibition activity of each cryoprotectant was further investigated through optical microscopy (Figure A), showing that the cryoprotectants could possess different recrystallization temperatures, among which DMSO (−31 °C) and glycerol (−28 °C) showed lower ones than the NADESs (−20––18 °C), indicating that the NADESs could be more effective to resist the temperature variations during cryopreservation.…”

“…64 Hence, cryoprotectants showing the ability to limit the ice crystal growth, decrease the crystal size, and control the crystal shape are highly pursued nowadays. 7 After evaluating the antifreezing capacity, the ice recrystallization inhibition activity of each cryoprotectant was further investigated through optical microscopy (Figure 6A), showing that the cryoprotectants could possess different recrystallization temperatures, among which DMSO (−31 °C) and glycerol (−28 °C) showed lower ones than the NADESs (−20−−18 °C), indicating that the NADESs could be more effective to resist the temperature variations during cryopreservation. After maintaining the corresponding temperatures for 30 min, the profiles of ice crystals in their initial and final stages were compared, exhibiting a tendency of increasing crystal size but decreasing crystal number in different degrees due to the fact that smaller ice crystals showing larger surface-to-volume ratios would be thermodynamically unstable and would tend increase their size to decrease the surface energy, 3 finally resulting in the less but bigger crystals.…”

“…Utilizing the phase transition of water and controlling the nucleation and growth of ice crystals, a series of pivotal freezing techniques have been invented and brought into human horizons, − bringing convenience to modern human life and adding value to various mega-industries . While in more hidden microworlds, cryotechnologies also play crucial roles in keeping the normal running of the human society and scientific research in many branches broadly involving biomedicine, clinical medicine, embryo and tissue engineering, cell and gene therapy, and so on. − For all these areas, cryopreservation is an indispensable technique, which can maintain the cellular life and keep activity for a long term by slowing down biochemical processes at subzero temperature …”

Plasmonic CuxS Nanocages for Enhanced Solar Photothermal Cell Warming

“…Cell freezing techniques are used to preserve cells with cryoprotectants below the freezing point. − However, cell resuscitation still remains a challenge due to the low cell viability after the thawing process. ,, The traditional water bath recovery method often leads to ice recrystallization of cell sap near the equilibrium point, and the cell will be dehydrated during its resuscitation process. − Although studies have shown that certain types of cell preservation medium are helpful in cryopreservation, − in order to obtain a satisfying survival rate of cells, high temperature elevation rate should be applied to escape the recrystallization zone. ,, …”