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

Project description:Ice formation is a ubiquitous process that poses serious challenges for many areas. Nature has evolved a variety of different mechanisms to regulate ice formation. For example, many cold-adapted species produce antifreeze proteins (AFPs) and/or antifreeze glycoproteins (AFGPs) to inhibit ice recrystallization. Although several synthetic substitutes for AF(G)Ps have been developed, the fundamental principles of designing AF(G)P mimics are still missing. In this study, we explored the molecular dynamics of ice recrystallization inhibition (IRI) by poly(vinyl alcohol) (PVA), a well-recognized ice recrystallization inhibitor, to shed light on the otherwise hidden ice-binding mechanisms of chain polymers. Our molecular dynamics simulations revealed a stereoscopic, geometrical match between the hydroxyl groups of PVA and the water molecules of ice, and provided microscopic evidence of the adsorption of PVA to both the basal and prism faces of ice and the incorporation of short-chain PVA into the ice lattice. The length of PVA, i.e., the number of hydroxyl groups, seems to be a key factor dictating the performance of IRI, as the PVA molecule must be large enough to prevent the joining together of adjacent curvatures in the ice front. The findings in this study will help pave the path for addressing a pressing challenge in designing synthetic ice recrystallization inhibitors rationally, by enriching our mechanistic understanding of IRI process by macromolecules.

| S-EPMC8606117 | biostudies-literature

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

Project description:Antifreeze (glyco)proteins (AF(G)Ps) have potent ice recrystallisation inhibition (IRI) activity - a desirable phenomenon in applications such as cryopreservation, frozen food and more. In Nature AF(G)P activity is regulated by protein expression levels in response to an environmental stimulus; temperature. However, this level of regulation is not possible in synthetic systems. Here, a synthetic macromolecular mimic is introduced, using supramolecular assembly to regulate activity. Catechol-terminated poly(vinyl alcohol) was synthesised by RAFT polymerization. Upon addition of Fe3+, larger supramolecular star polymers form by assembly with two or three catechols. This increase in molecular weight effectively 'switches on' the IRI activity and is the first example of external control over the function of AFP mimetics. This provides a simple but elegant solution to the challenge of external control of AFP-mimetic function.

| S-EPMC5166974 | biostudies-literature

Thermal conductivity enhancement in electrospun poly(vinyl alcohol) and poly(vinyl alcohol)/cellulose nanocrystal composite nanofibers.

Project description:The thermal conductivity enhancement of neat poly(vinyl alcohol) and poly(vinyl alcohol) (PVA)/cellulose nanocrystal (CNC) composite was attempted via electrospinning. The suspended microdevice technique was applied to measure the thermal conductivity of electrospun nanofibers (NFs). Neat PVA NFs and PVA/CNC NFs with a diameter of approximately 200 nm showed thermal conductivities of 1.23 and 0.74 W/m-K, respectively, at room temperature, which are higher than that of bulk PVA by factors of 6 and 3.5, respectively. Material characterization by Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis confirmed that the thermal conductivity of the PVA/CNC NFs was enhanced by the reinforcement of their backbone rigidity, while that of the neat PVA NFs was attributed to the increase in their crystallinity that occurred during the electrospinning.

| S-EPMC6395720 | biostudies-literature

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

Project description:Poly(vinyl alcohol) (PVA) is the most active synthetic mimic of antifreeze proteins and has extremely high ice recrystallization inhibition (IRI) activity. Addition of PVA to cellular cryopreservation solutions increases the number of recovered viable cells due to its potent IRI, but it is intrinsically nondegradable in vivo. Here we report the synthesis, characterization, and IRI activity of PVA containing degradable ester linkages. Vinyl chloroacetate (VClAc) was copolymerized with 2-methylene-1,3-dioxepane (MDO) which undergoes radical ring-opening polymerization to install main-chain ester units. The use of the chloroacetate monomer enabled selective deacetylation with retention of esters within the polymer backbone. Quantitative IRI assays revealed that the MDO content had to be finely tuned to retain IRI activity, with higher loadings (24 mol %) resulting in complete loss of IRI activity. These degradable materials will help translate PVA, which is nontoxic and biocompatible, into a range of biomedical applications.

| S-EPMC5792090 | biostudies-literature

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.

| S-EPMC5718289 | biostudies-other

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.

Project description:Poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) named further PVBA was investigated as a protective coating for copper corrosion in 0.9% NaCl solution using electrochemical measurements such as, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization associated with atomic force microscopy (AFM). The PVBA coating on the copper surface (Cu-PVBA) was modeled in methanol containing PVBA. Its inhibitory properties against corrosion was comparatively discussed with those of the copper sample treated in methanol without polymer (Cu-Me) and of untreated sample (standard copper). A protective performance of PVBA coating of 80% was computed from electrochemical measurements, for copper corrosion in NaCl solution. Moreover, AFM images designed a specific surface morphology of coated surface with PVBA, clearly highlighting a polymer film adsorbed on the copper surface, which presents certain deterioration after corrosion, but the metal surface was not significantly affected compared to those of untreated samples or treated in methanol, in the absence of PVBA.

| S-EPMC7037414 | biostudies-literature

The relevance of nanoscale biological fragments for ice nucleation in clouds.

Project description:Most studies of the role of biological entities as atmospheric ice-nucleating particles have focused on relatively rare supermicron particles such as bacterial cells, fungal spores and pollen grains. However, it is not clear that there are sufficient numbers of these particles in the atmosphere to strongly influence clouds. Here we show that the ice-nucleating activity of a fungus from the ubiquitous genus Fusarium is related to the presence of nanometre-scale particles which are far more numerous, and therefore potentially far more important for cloud glaciation than whole intact spores or hyphae. In addition, we quantify the ice-nucleating activity of nano-ice nucleating particles (nano-INPs) washed off pollen and also show that nano-INPs are present in a soil sample. Based on these results, we suggest that there is a reservoir of biological nano-INPs present in the environment which may, for example, become aerosolised in association with fertile soil dust particles.

| S-EPMC4308702 | biostudies-literature

Poly(ethylene glycol)-poly(vinyl alcohol)-adamantanate: synthesis and stimuli-responsive micelle properties.

Project description:A pH-sensitive amphiphilic polymer based on poly(vinyl alcohol) (PVA), modified with poly(ethylene glycol) (PEG) and adamantane (Ad) pendant groups, has been synthesized and the self-assembly properties of this PEG-PVA-Ad construct investigated. PEG-PVA-Ad polymer forms micelles via self-assembly at concentrations as low as 26 mg L-1. These polymer micelles can be destroyed by low pH or the addition of ?-CD.

| S-EPMC6906925 | biostudies-literature

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