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Probing the Biomimetic Ice Nucleation Inhibition Activity of Poly(vinyl alcohol) and Comparison to Synthetic and Biological Polymers.

ABSTRACT: Nature has evolved many elegant solutions to enable life to flourish at low temperatures by either allowing (tolerance) or preventing (avoidance) ice formation. These processes are typically controlled by ice nucleating proteins or antifreeze proteins, which act to either promote nucleation, prevent nucleation or inhibit ice growth depending on the specific need, respectively. These proteins can be expensive and their mechanisms of action are not understood, limiting their translation, especially into biomedical cryopreservation applications. Here well-defined poly(vinyl alcohol), synthesized by RAFT/MADIX polymerization, is investigated for its ice nucleation inhibition (INI) activity, in contrast to its established ice growth inhibitory properties and compared to other synthetic polymers. It is shown that ice nucleation inhibition activity of PVA has a strong molecular weight dependence; polymers with a degree of polymerization below 200 being an effective inhibitor at just 1 mg.mL(-1). Other synthetic and natural polymers, both with and without hydroxyl-functional side chains, showed negligible activity, highlighting the unique ice/water interacting properties of PVA. These findings both aid our understanding of ice nucleation but demonstrate the potential of engineering synthetic polymers as new biomimetics to control ice formation/growth processes.

SUBMITTER: Congdon T

PROVIDER: S-EPMC4577968 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Poly(vinyl alcohol) Molecular Bottlebrushes Nucleate Ice.

Project description:Ice binding proteins (IBP) have evolved to limit the growth of ice but also to promote ice formation by ice-nucleating proteins (INPs). IBPs, which modulate these seemingly distinct processes, often have high sequence similarities, and molecular size/assembly is hypothesized to be a crucial determinant. There are only a few synthetic materials that reproduce INP function, and rational design of ice nucleators has not been achieved due to outstanding questions about the mechanisms of ice binding. Poly(vinyl alcohol) (PVA) is a water-soluble synthetic polymer well known to effectively block ice recrystallization, by binding to ice. Here, we report the synthesis of a polymeric ice nucleator, which mimics the dense assembly of IBPs, using confined ice-binding polymers in a high-molar-mass molecular bottlebrush. Poly(vinyl alcohol)-based molecular bottlebrushes with different side-chain densities were synthesized via a combination of ring-opening metathesis polymerization (ROMP) and reversible addition-fragmentation chain-transfer (RAFT) polymerization, using "grafting-to" and "grafting-through" approaches. The facile preparation of the PVA bottlebrushes was performed via selective hydrolysis of the acetate of the poly(vinyl acetate) (PVAc) side chains of the PVAc bottlebrush precursors. Ice-binding polymer side-chain density was shown to be crucial for nucleation activity, with less dense brushes resulting in colder nucleation than denser brushes. This bio-inspired approach provides a synthetic framework for probing heterogeneous ice nucleation and a route toward defined synthetic nucleators for biotechnological applications.

| S-EPMC9748936 | biostudies-literature

Molecular Dynamics at the Interface between Ice and Poly(vinyl alcohol) and Ice Recrystallization Inhibition.

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| S-EPMC8606117 | biostudies-literature

Activation of Ice Recrystallization Inhibition Activity of Poly(vinyl alcohol) using a Supramolecular Trigger.

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Synthesis of Degradable Poly(vinyl alcohol) by Radical Ring-Opening Copolymerization and Ice Recrystallization Inhibition Activity.

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Water absorption dependence of the formation of poly(vinyl alcohol)-iodine complexes for poly(vinyl alcohol) films.

Project description:Poly(vinyl alcohol) (PVA) films annealed at different temperatures are used to explore the effects of the water absorption on the formation of PVA-iodine complexes. It's found that the higher the annealing temperature, the stronger the interaction force between PVA segments, and the smaller the free volume of the PVA films. These mainly lead to the reduction of the amount of PVA segments with a moderate degree of hydration (i.e., PVA segments with moderate mobility), which are the major segments participating in the formation of PVA-iodine complexes. Therefore, PVA films with higher water absorption not only possess faster complexation speed and form more PVA-iodine complexes, but also increase the proportion of polyiodide ions with a longer length. Moreover, the complexation restricts the PVA segments with high mobility, resulting in the formation of the intermolecular ordered structure. The water absorption dependence may guide the dyeing process to obtain PVA polarizers with excellent optical performance.

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Ultra-Low Dispersity Poly(vinyl alcohol) Reveals Significant Dispersity Effects on Ice Recrystallization Inhibition Activity.

Project description:Polymer mimics of antifreeze proteins are emerging as an exciting class of macromolecular cryoprotectants for the storage of donor cells and tissue. Poly(vinyl alcohol), PVA, is the most potent polymeric ice growth inhibitor known, but its mode of action and the impact of valency (DP) are not fully understood. Herein, tandem RAFT polymerization and column chromatography are used to isolate oligomers with dispersities <1.01 to enable the effect of molecular weight distribution, as well as length, to be probed. It is found that polymers with equal number average molecular weight, but lower dispersity, have significantly less activity, which can lead to false positives when identifying structure-property relationships. The minimum chain length for PVA's unique activity, compared to other non-active poly-ols was identified. These results will guide the design of more active inhibitors, better cryopreservatives and a deeper understanding of synthetic and biological antifreeze macromolecules.

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Influence of Block Copolymerization on the Antifreeze Protein Mimetic Ice Recrystallization Inhibition Activity of Poly(vinyl alcohol).

Project description:Antifreeze (glyco) proteins are produced by many cold-acclimatized species to enable them to survive subzero temperatures. These proteins have multiple macroscopic effects on ice crystal growth which makes them appealing for low-temperature applications-from cellular cryopreservation to food storage. Poly(vinyl alcohol) has remarkable ice recrystallization inhibition activity, but its mode of action is uncertain as is the extent at which it can be incorporated into other high-order structures. Here the synthesis and characterization of well-defined block copolymers containing poly(vinyl alcohol) and poly(vinylpyrrolidone) by RAFT/MADIX polymerization is reported, as new antifreeze protein mimetics. The effect of adding a large second hydrophilic block is studied across a range of compositions, and it is found to be a passive component in ice recrystallization inhibition assays, enabling retention of all activity. In the extreme case, a block copolymer with only 10% poly(vinyl alcohol) was found to retain all activity, where statistical copolymers of PVA lose all activity with very minor changes to composition. These findings present a new method to increase the complexity of antifreeze protein mimetic materials, while retaining activity, and also to help understand the underlying mechanisms of action.

| S-EPMC5022065 | biostudies-literature

Design and evaluation of nano-hydroxyapatite/poly(vinyl alcohol) hydrogels coated with poly(lactic-co-glycolic acid)/nano-hydroxyapatite/poly(vinyl alcohol) scaffolds for cartilage repair.

Project description:BackgroundPoly(vinyl alcohol) (PVA) hydrogels have been widely used in synthetic cartilage materials. However, limitations of PVA hydrogels such as poor biomechanics and limited cell ingrowth remain challenges in this field.MethodsThis work aimed to design novel nano-hydroxyapatite (nano-HA)/poly(vinyl alcohol) (PVA) hydrogels coated with a poly(lactic-co-glycolic acid) (PLGA)/nano-HA/PVA scaffold to counter the limitations of PVA hydrogels. The core, comprising nano-HA/PVA hydrogel, had the primary role of bearing the mechanical load. The peripheral structure, composed of PLGA/nano-HA/PVA, was designed to favor interaction with surrounding cartilage.ResultsThe double-layer HA/PVA hydrogel coated with PLGA/HA/PVA scaffold was successfully prepared using a two-step molding method, and the mechanical properties and biocompatibility were characterized. The mechanical properties of the novel PLGA/HA/PVA scaffold modified HA/PVA hydrogel were similar to those of native cartilage and showed greater sensitivity to compressive stress than to tensile stress. Rabbit chondrocytes were seeded in the composites to assess the biocompatibility and practicability in vitro. The results showed that the peripheral component comprising 30 wt% PLGA/5 wt% HA/15 wt% PVA was most conducive to rabbit chondrocyte adhesion and proliferation.ConclusionsThe study indicated that the double-layer HA/PVA hydrogel coated with PLGA/HA/PVA scaffold has the potential for cartilage repair.

| S-EPMC6916227 | biostudies-literature

Poly (Vinyl Butyral-Co-Vinyl Alcohol-Co-Vinyl Acetate) Coating Performance on Copper Corrosion in Saline Environment.

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| S-EPMC7037414 | biostudies-literature

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