Gibson Group News
Paper Published in ACS MacroLetters
Our latest work has been published in ACS Macroletters. This is a collaboration with Rachel O'Reillys group, and was undertaken by Lewis Blackman. Complex materials containing thermoresponsive polymers have been extensively studied. However, there are still conflicting reports on their transition temperatures and hysteresis values. Here we synthesised a range of polymeric micelles with a thermoresponsive corona. By changing the nature of the core forming block, we could vary the aggregation number (number of chains per micelle) and explore the effect of this on the responsive transitions. It was found that the actual transition temperature did not strongly vary with NAgg, but that the hysteseis was strongly affected. We hypothesise that the nature of the core (whcih was in some cases relatively hydrophilic) promoted solubilisation. Importantly, this shows that the nature of the macromolecular assembly, not just the chemical structure of the polymer, is a crucial parameter in predicting the properties of such materials
Read the paper here
Effect of Micellization on the Thermoresponsive Behavior of Polymeric Assemblies
Paper published in Polymer Chemistry
Or latest paper has been published in RSC Polymer Chemistry. This is a collaboration with Jon Rourke and Neil Wilson (physics). Since its discovery, a huge number of scientists (academic and industrial) have sought to investigate the applications of graphene, and its relatives carbon nanotubes. It's unique 2-D structure gives rise to intresting properties, but a key challenge lies in ensure it can be compatitablised - mixed - with other components. To acheive this polymer conjugation is a useful approach. This is normally acheived through complex multi-step procedures. Here we show that base-washed graphene oxide (an easy and scalable derivative of graphene) can be modified by RAFT-ed polymers by ring-opening of surface epoxides using the thiol-end group. This was proven using a range of high resolution analytical techniques, including solid state NMR, TEM and XPS. We beleive the simplicity of the method will enable more complex hybrid material to be developed.
Read the paper here
One-step grafting of polymers to graphene oxide"
http://pubs.rsc.org/en/content/articlelanding/2015/py/c5py01358e#!divAbstract
Paper Published in Biomacromolecules
Our latest work on antifreeze protein mimetic macromolecules has been published in ACS Biomacromolecules. We are seeking to understand and explain ice recystallisation inhibition - a unique property associated with antifreeze proteins which we have shown to be a useful property to enhance cryopreservation (see 2015, 51, 12977-12980 Chemical Communications or Nature Commun, 2014, 5, 3244). Few materials can produce this property. Here we built on previous observations that c-type lectins (carbohydrate binding proteins) had evolutionary relationships to AFPs, but by using non-homologous plant lectins. Interestingly, these only have activity in the presence of Ca2+, which is also required for sugar-binding, suggesting a relationship. Furthermore, we also show that a simple antibacterial peptide, Nisin A, also has ice inhibition activity, based on amphiphilicity. Whilst these were not as active as polymers we have previosly identified this provides a biological route to AFP mimetics, which offers many advantages.
Read the paper here.
Bethany Dean wins Award to Present Science in Australia
A Warwick Chemistry undergraduate researcher, Bethany Dean who has done several projects in our lab has won an award to allow her to travel to Australia (!) to attend the ICUR undergraduate reserach conference . She will present her work on understanding how synthetic polymers affect ice nucleation - A process which is still not understood despite its obvious important in process from cloud formation, to cryopreservation to making ice cream!
Read her paper on this topic here (with another undergrad student, Jamie Kasperczak-Wright);
Paper Published in Biomacromolecules
Our latest work on biochemically adaptable polymers has been accepted for publication in ACS Biomacromolecules, as part of a collaboration with Dr. Fran. Greco at Uni. Reading Pharmacy. There has been much interest in last decade in polymers with LCST behaviour (become less soluble when they are heated), and this responsive behaviour has been suggested to be useful for biomedical/nano-delivery applications. However, applying a raised temperature in vivo is pretty challenging, and not practical for most treatments. We have expanded the concept of an isothermal transition (see our review here) where we use a thermo-responsive polymer but 'train' it to respond to biochemical stimuli. In this work we synthesised polymers based on poly(oligoethyleneglycol methacylate) which can respond to alkaline phosphatase - a secreted enzyme found in most mammals. We showed that the polymer is stable under normal physiological conditions, but addition of the enzyme causes a rapid phase change - this can be considered to be a change in LogP; one of the key characteristic of a molecules pharmacokinetics.Read the paper here;
Paper Published in Biomacromolecules
Our latest paper on the interactions between ice and synthetic polymers has been published in ACS Biomacromolecules. This paper is our first study in ice nucleation - distinct from ice growth inhibition. Previous work has shown that PVA can inhibit ice nucleation, but this was studied using broad dispersity, partially acetylated commercial PVA. Using RAFT/MADIX we studied the effect of molecular weight on ice nucleation inhibition activity of PVA. This revealed clear molecular weight-dependant behaviour. Interesting, signficant activity require longer polymer chains than required for ice growth inhibition, which may help us understand these processes in the future. A range of other synthetic polymers were shown to have essentially no ice nucleation activity, highlighting (once again) the unique properties of PVA. Much of this work was conducted by undergraduate students, Bethany Dean and Jamie-Kasperzick Wright
Paper accepted in ACS Biomaterials Science and Enginnering
Our most recent cryopreservation/antifreeze protein mimetic paper has been accepted in the new ACS Journal, Biomaterials Science and Enginneering. In this work we sought to develop an 'all polymer' cryopreservation solution based upon ice recrystalisation inhibiting polymers. We have previously shown that PVA is a potent ice growth inhibitor and used this to preserve red blood cells. However, the total recovery using these polymers alone was not high enough for translation to real application. In this paper we used hydroxyethyl starch as a non-vitrifying cryopreservative, in tandem with our ice-modulating polymers. THis enabled us to recover far higher amounts of red blood cells, post freezing. Compared to glycerol (the current state of the art), this system was easier to use (no equilibration time issues) and all compounds are non-cell penetrating - meaning easy removal post thawing. A secondary benefit of an 'all polymer' system is the low molar concentration of cryoprotectants enabling us to succesfully store blood at - 20 C; a temperature where glycerol systems would still be liquid.
Read the paper here
MRC Innovation Grant Awarded
In collaboration with Dr. Elizabeth Fullam (Life Sciences), we have been awarded a grant from the Medical Research Council (MRC) from the Cross Council AMR Theme 1 Initiative (1 of only 8 awards made). This will seek to develop new tools for targetting the cell wall of Tuberculosis to validate new antibacterial and diagnostic agents. There is a 2 year postdoctoral position associated with this grant, so please contact us if interested.