Gibson Group News
Review Article in ChemSocRev
We have published our latest review, with the O'Reilly Group. This review article discussed the effects of disperstiy on polymer self assembly processes, and applications. This covers the length scales from monomer sequence dispersity to the final self-assembled particles. This provides crucial discussion on if 'narrow dispersity' is needed, and how narrow is needed. The impact of the above on developments in controlled polymerizations is also made.
Read the article here in Chem. Soc. Rev.
Dispersity effects in polymer self-assemblies: a matter of hierarchical control
Paper Published in Polymer Chemistry
In this paper, two initiation methods in polymerization-induced self-assembly PISA were studied in depth in order to compare the morphological phase diagram outcomes of these processes.This is part of our ongoign interest in creating polymers and nanomaterials to mimic Nature's complexitiy - in this case, self assembly. The first process was light-mediated initiator-free PISA and the second was thermal initiation with the use of an azo- initiator. We found that light-mediated PISA (photo-PISA) formed structures that were generally of higher order to those formed by thermal initiation. The influence of the light intensity was studied as was the end group retention of the resulting polymers from each process. It was found that the end group fidelity decreased as a function of light intensity and irradiation time. The differences between the phase diagrams obtained by the two original processes were therefore attributed to a combination of the reaction kinetics and the degree of end group fidelity. Irradiating pre-formed nano-objects for extended periods of time was able to induce a worm-to-vesicle morphology transition by removal of the trithiocarbonate end group. It is anticipated that this work will further the understanding of photo-PISA in relation to thermal PISA, both of which have gained tremendous interest in recent years.
Read the paper here
Anti-Bacterial Polymers Published in Biomacromolecules
Our latest work, in collaboration with the Fullam group at the School of Life Sciences has been published in ACS Biomacromolecules. This is part of our larger collaboration, including an Innovation grant from the MRC, into new methods for addressing the challenge of antimicrobial resistance. Traditional antimicrobials function by targetting a specific enzyme/pathway, which often enables resistance to develop. We are interested in moving from single target/small molecule paradigm to more innovative targets. In this work, we wanted to evaluate cationic polymers as anti-mycobacterial agents. Cationic polymers are extremely well studied, but mostly against pathogenic gram-negative organisms. Mycobacteria, which are a unique class of gram positive micro-organisms, which include Mycobaterium Tuberculosis have not been studied. We found that poly(dimethyl aminoethyl methacrylate) was particularly potent against a non-pathogenic mycobacterium (M. smegmatis). Interestingly, the polymer did not appear to lyse the cell membranes, which is the assumed mode of action, but less active cationic polymers did. Electron microscopy analysis suggested the cell-walls were being stressed. We are currently investigating this in more detail.
Read the full paper here
Paper Published in British Journal of Pharmacology
Our recent work towards developing new antibacterial agents to treat tuberculosis has been published in the British Journal of Pharmacology. Tuberculosis is a major global health threat and is currently the leading cause of death from a single infectious agent worldwide. The current treatment regime requires a cocktail of antibiotics to be taken for at least 6 months with numerous side effects, and resistant forms are becoming more wide-spread; there is an urgent need for new drugs.
This project was lead by Dr Elizabeth Fullam from the School of Life Scieinces and investigated the antibacterial properties of a piperindol compound and its corresponding bis-Mannich base against Mycobacterium smegmatis (a model organism for Mycobacterium tuberculosis) and Gram-negative organisms. The two compounds were found to be selective for mycobacteria, rapidly killing, with a selectivity index of >30 fold. Spontaneous resistant mutants to the compounds were also generated to allow identification of the target of these compounds. Our results highlight the piperidinol moiety as an attractive compound class in the development of novel anti-tubercular agents.
Read the paper here
Identification of the anti-mycobacterial functional properties of piperidinol derivatives
Paper Published in Biomaterials Science
Our latest work from a collaboration with researchers at Johannes Gutenberg University in Mainz has been published in Biomaterial Science. This research stemmed from a research visit by Dr Christian Freese (the lead author) to the Gibson Lab, building on our previous collaborations.
In this work, cell culture models that more closely reproduce the in vivo environment were used to investigate the impact of PEGylated AuNPs on endothelial cells. The traditional static culture techniques that do not accurately represent the stretch and shear-stress that endothelial cells undergo continuously in vivo, were replaced by culturing the cells under flow and stretch conditions and the resulting cellular stress and function were probed. Due to no toxic effect, cell stress or inflammatory response being observed in these assays, is was concluded that PEGylated gold nanoparticles could be a useful tool for medical applications. Also using these models for cell viability studies could reduce animal experiments and drug development costs.
Read the paper here
Gold nanoparticle interactions with endothelial cells cultured under physiological conditions
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.
Read the paper here
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