Antifreeze (Glyco)protein Mimetic Behavior of Poly(vinyl alcohol): Detailed Structure Ice Recrystallization Inhibition Activity Study

Abstract

This manuscript reports a detailed study on the ability of poly(vinyl alcohol) to act as a biomimetic surrogate for antifreeze(glyco)proteins, with a focus on the specific property of ice-recrystallization inhibition (IRI). Despite over 40 years of study, the underlying mechanisms that govern the action of biological antifreezes are still poorly understood, which is in part due to their limited availability and challenging synthesis. Poly(vinyl alcohol) (PVA) has been shown to display remarkable ice recrystallization inhibition activity despite its major structural differences to native antifreeze proteins. Here, controlled radical polymerization is used to synthesize well-defined PVA, which has enabled us to obtain the first quantitative structure-activity relationships, to probe the role of molecular weight and comonomers on IRI activity. Crucially, it was found that IRI activity is "switched on" when the polymer chain length increases from 10 and 20 repeat units. Substitution of the polymer side chains with hydrophilic or hydrophobic units was found to diminish activity. Hydrophobic modifications to the backbone were slightly more tolerated than side chain modifications, which implies an unbroken sequence of hydroxyl units is necessary for activity. These results highlight that, although hydrophobic domains are key components of IRI activity, the random inclusion of addition hydrophobic units does not guarantee an increase in activity and that the actual polymer conformation is important.

RAFT Polymerization of Vinyl Esters: Synthesis and Applications

“…VPr [72] VBu [3,4] VPiv [4,6,30,31,68,69] VOc [4] VNDec [69][70][71] VSt [70] VBz [30,31,67] VClAc [34,73] VTFAc [7,9] iPAc [74] CF 3 VAc [8] The halogenated esters vinyl chloroacetate (VClAc) [34,73] and VTFAc [7,9] are more susceptible to hydrolysis than VAc. Block copolymers of these monomers with VAc allow the preparation of PVA-PVAc block copolymers by selective hydrolysis [9,34].…”

“…The isopropenyl esters isopropenyl acetate (iPAc) [74] and 1-(trifluoromethyl)vinyl acetate (CF 3 VAc) [8] have been copolymerized with VAc. Addition of 10% iPAc or CF 3 VAc to a VAc polymerization had no effect on the control of the polymerization.…”

Influence of Polymer Chain Architecture of Poly(vinyl alcohol) on the Inhibition of Ice Recrystallization

“…[ 14 ] Furthermore, minor changes in the confi guration of the sugar moiety, and the presence of acetyl or methyl groups can signifi cantly alter the antifreeze activity. [ 15,16 ] The effect of molecular weight on the ice recrystallization inhibition (IRI) activity of PVA has been well described by Congdon et al [ 6 ] One unexplored research direction is the effect of main chain architecture on the IRI activity of PVA. Over the past two decades, advances in polymer sciences in living/controlled radical polymerization techniques have led to the design and synthesis of novel macromolecular architectures, such as block copolymers, branched and dendritic polymers, molecular bottlebrushes, etc.…”

“…[1][2][3] PVA has furthermore been found to adhere to ice-surfaces and inhibit the recrystallization processes of ice, which withholds great potential in the development of innovative cryopreservation and anti-icing technologies. [4][5][6][7] The effi cient cryopreservation of human red blood cells by addition of only 0.1 wt% PVA was recently reported, which attained a signifi cant increase in cell recovery. [ 8 ] Compared to biological antifreeze polymers such as antifreeze glycoproteins (AFGPs), PVA has the advantage that it is inexpensive and can be produced in large quantities.…”

Combining Biomimetic Block Copolymer Worms with an Ice‐Inhibiting Polymer for the Solvent‐Free Cryopreservation of Red Blood Cells

“…To evaluate whether the PGMA 56 ‐PHPMA 155 worms exhibited IRI behavior, they were assayed using the standard “splat” test and compared to poly(vinyl alcohol) (PVA), which is a potent IRI‐active polymer 14. Briefly, this assay involves creating a 10 μm thick wafer of small ice crystals, which are then annealed at −6 °C for 30 min before determining the mean largest grain size (MLGS) of the ice crystals (with smaller ice crystals indicating higher activity).…”