The atomistic details of the ice recrystallisation inhibition activity of PVA

Abstract

Understanding the ice recrystallisation inhibition (IRI) activity of antifreeze biomimetics is crucial to the development of the next generation of cryoprotectants. In this work, we bring together molecular dynamics simulations and quantitative experimental measurements to unravel the microscopic origins of the IRI activity of poly(vinyl)alcohol (PVA)—the most potent of biomimetic IRI agents. Contrary to the emerging consensus, we find that PVA does not require a “lattice matching” to ice in order to display IRI activity: instead, it is the effective volume of PVA and its contact area with the ice surface which dictates its IRI strength. We also find that entropic contributions may play a role in the ice-PVA interaction and we demonstrate that small block co-polymers (up to now thought to be IRI-inactive) might display significant IRI potential. This work clarifies the atomistic details of the IRI activity of PVA and provides novel guidelines for the rational design of cryoprotectants.

Ice Recrystallization Inhibition by Amino Acids: The Curious Case of Alpha- and Beta-Alanine

“…For AFPs, the size of the molecule or area of its ice binding site is known to correlate strongly with antifreeze activity. 43 , 44 Our previous work 38 also revealed that, for the flexible polymer PVA, the effective volume and contact area with the ice surface can also determine the strength of IRI. Therefore, we first computed the volume and solvent-accessible surface area (SASA) occupied by these two molecules throughout the course of the simulations.…”

Chemical approaches to cryopreservation

“…Molecular modelling techniques offer an opportunity to probe processes that cannot be visualized experimentally due to limits in spatial and temporal resolution, such as capturing rates of water crystallization that lead to homogeneous nucleation 187 . Modelling also offers the chance to explore the structure–function relationships of cryoprotectants and their interactions with ice, such as probing the ice recrystallization inhibition mechanism of PVA and synthetic copolymers using molecular dynamic simulations 188 and assessing the ice nucleation abilities of crystalline surfaces 189 . Properties of small-molecule cryoprotectants have also been investigated, including the interaction of DMSO with model lipid membranes 190 , as well as the hydrogen-bonding networks of water with glycerol 191 .…”

Natural Cryoprotective and Cytoprotective Agents in Cryopreservation: A Focus on Melatonin

“…In this context, ice recrystallization is an important process to control during cryopreservation in order to prevent cold-induced damages. This is a form of Ostwald ripening, where larger ice crystals are formed at the expense of smaller ones, which causes osmotic stress and even cell death (reviewed elsewhere in [ 36 ]). NPA can be used to prevent the damage of ice recrystallization, including for example polyvinyl alcohols and polyampholyte-based CPAs, which are synthetic polymers of different sizes and levels of biocompatibility.…”