Gibson Group News
Paper published in Biomacromolecules
Our latest work investigating the role of regiochemistry in the design of synthetic ice recrystallisation inhibiting materials has been published in Biomacromolecules. We have previously shown that poly(ampholytes) (mixed positive and negative charges) are an exciting class of synthetic materials which display IRI activity while also being highly tuneable, compared to poly(vinyl alcohol), the only other potent polymer IRI. In this work we overcame two challenges of making ampholytes by conventional polymerization; Obtaining an exact 1:1 ratio of the charges and ensuring a perfectly alternating structure. This was achieved by using maleic anhydride copolymers, which has a propensity to cross propagate. This level of sequence control is unusual for most polymerisation reactions and can only be achieved through specific monomer combinations. The activity of these polymers with a range of comonomers and pendant amine groups was investigated and increasingly hydrophobic side chains (but not backbones) increased activity.
These polymers were then compared to a structurally similar polymer in which the charged groups are randomly incorporated, which had less activity, demonstrating for the first time that polymer sequence actually has a large impact on this property.
Read the paper here
Paper published in Journal of Polymer Science Part A
Our latest work has been published in the Journal of Polymer Science Part A. In this work we have synthesised and characterised gold nanoparticles coated with RAFT-synthesised polymer chains. We describe how the two different polymer coatings effect the properties of the nanoparticles, in the context of grafting density, buffer stability, and in a lectin binding assay. We found that poly(oligoethylene glycol methacrylates), despite being widely used particle coatings, lead to low grafting densities which in turn resulted in lower stability in biological buffers. In comparison poly(vinylpyrrolidones) resulted in stable particles with higher grafting densities due to the compact size of each monomer unit. This work forms a link between our previous studies on the polymer coating of gold nanoparticles and the surface grafting of polymers onto gold and glass supports. These results will guide the development of new nanoparticle biosensors with enhanced specificity, affinity, and stability both within our research group and the wider scientific community.
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Paper published in Antonie van Leeuwenhoek
Our latest work, in collaboration with Michela Corsaro in Naples has been published. We are very interested in identifying new biological macromolecules which can interact with ice, or act as cryoprotecants for cells (or organisms) in extreme environments, as new targets for synthetc mimics. In this work, the Corsaro group synthesised sulphated polysaccharides, related to previously identified cryoprotecant polysaccharides. Detailed structural chracteriseation was undertaken. Surprisingly, it was found to have far weaker ice recrystalisation activity than the polysaccharide extracted from the extremophile organism (Colwellia psychrerythraea) indicating that some other structural features are involved in its function.
Read the paper here
New Paper in European Polymer Journal
Our latest work investigating how the architecture (shape) of synthetic ice growth inhibitors affects their function is now online in the European Polymer Journal. We have previously shown that poly(vinyl alcohol) is a potent inhibitor of ice crystal growth; a proeprty normally only found in antifreeze (glyco) proteins from polar fish species. We have also found that inhibiting ice growth lets us enhance the cryopreservation of donor cells, for regenerative medicine. However, we are still not certain of how this polymer functions. In this work, we developed a new tri-functional RAFT (or MADIX) agent to enable us to make 3-arm, star branched polymers. We foudn that the third arm was essentiall non-active, having the same activity as a 2-arm star (i.e. linear polymer). This suggests that hydrodynamic volume, not valancy (number of potental binding sites) is the key marker of activity and might suggest that the mode of action is not entirely due to direct ice binding
Read the paper here
Synthesis of Star-Branched Poly(vinyl alcohol) and Ice Recrystallization Inhibition Activity
Paper Published in Biomacromolecules
Our latest work has been published in ACS Biomacromolecules. This paper describes our latest progress in the design, understanding and application of synthetic polymers to mimic the function of antifreeze proteins. We have previously identified that poly(vinyl alcohol), PVA, is an excellent inhibitor of ice growth and can aid in the cryopreservation of cells. However, we do not really understand why it works so well, compared to other similar polymers. To address this, we made use of block copolymerization with a non-antifreeze active hydrophilic second polymer. This is a major advantage of using polymers, not proteins, in that macromolecular architecture can be easily changed. Here we find that addition of very large second blocks have essentially no effect of the antifreeze proteins of the PVA - even with block co-polymers where 90% is non-active polymer the activity is retained. This is a surprise and we believe (but cannot prove yet) that this indicates our PVAs do not bind the ice, but rather limit transfer of water at the quasi-liquid interface.
Read the paper here!
Paper Published in Journal of Materials Chemistry B
Our latest work has been published in the RSC Journal of Materials Chemistry B. This work forms part of our long standing interest in responsive nanomaterials - materials which can respond to biochemical (or external) triggers to promote a useful interaction. In particular we are interested in gold nanoparticles with responsive coronas. We have previously observed that the size of the particle core has a huge impact on the observed transition temperature of the hybrid particle. In this paper we investigated in detail the effect of mixing different sizes of particles, or identical particles with different polymers on them as a route to fine-tune the transition temperature; this is improtant as it removes the need to screen lots of polymers to obtain the desired response, as two 'master' batches can simply be mixed. In particular we found evidence for interaction betwen large/small particels with different transition temperatures, suggesting they have some cooperative aggregation behaviour. This, in particular, has applications and implications in the design of nanoparticle biosensors
Read the paper here
Post-Doc Vacancy
We have a vacancy for an ambitious and talented post-doc to joint our interdisciplinary team. The project will focus on using recombinant (bacterial expression) methods to generate protein-based biomaterials as new mimics of antifreeze proteins. The global aim of this work is to improve methods for the cryopreservation of donor cells and tissue for regenerative medicine.
Paper published in Nanotoxicology
Our latest work, as part of a long term collaboration with JGU Mainz, has been published in the leading toxicology journal Nanotoxicology. Despite the huge interest in nanomedicine and drug delivery, succesful (clinically relevant) strategies to deliver across complex barriers, especially the blood brain barrier (BBB) are still missing. Here, we used a combinatorial synthethetic strategy (see here) to make a small library of polymer-coated gold nanoparticles as model nanoparticles to probe their interaction with the human BBB. Rather than just simply testing for cytoxicity (i.e. concentration to cause cell death) a detailed study was undertaken at low concentrations to look for other markers of toxicity. It was found that certain nanoparticle formulations lead to upregulation of pro-inflammatory markers. It was also possible to rule out ER (endoplasmic reticulum) stress, which can lead to apoptosis (programmed cell death). The versatile synthetic methodology, and unique properties of gold (SPR band) and ability to quantify cell uptake usign ICP was crucial to this. Read the full paper here.