Gibson Group News
Potent ice recrystallisation inhibitors based on Phenyl Alanine Published
We are very interested in understand how ice binding proteins function, but also discovering the design rules to let us obtain synthetic mimics. Macromolecular mimics are now established, but obtaining structure-function relationships is challenging due to e.g. dispersity, and the computation cost of modelling large flexible polymers. In our latest work, as part of our collaboration with the Sosso Group, we discover that phenyl alanine (the amino acid) is a potent ice recrystallisaiton inhibitor. Modification of different parts of the molecule helped us identify the key motifs, including the need for hydrophobicity.
This work is published in ChemComm and is can be read here:
Slowing the growth of ice with amino acids
Ice binding proteins have been widely studied, and we have a large research program into macromolecular (polymer) cryoprotectants. There has been less work on the study of small molecules which can modulate ice formation and growth, however. In our latest work with the Sosso GroupLink opens in a new window we show that simple amino acids can reduce ice recrystallisation. L-alanine could inhibit, whereas beta-alanine did not. Modelling suggests incompatability with the ice lattice explains the activity, rather than intrinisic ice binding affinity. This work shows that the design and discovery of small molecules to control ice growth is possible.
Read the paper here
Detecting SARS-COV-2 Using Plasmonic Nanoparticles
Working with colleagues at UHCW, we have demonstrated the detection of SARS-COV-2 virus using liquid samples. Our team in 2020, discovered that SARS-COV-2 spike protein could bind sialic acids Link opens in a new window(specialised sugars) and developed this for lateral-flow and flow-through detection as the first example of a glyco-assay, Link opens in a new windowrather than more established anti-body based detection. In this present work, the team show a solution-phase assay which can be conducted in multiwell plates and is hence suitable for automation. The key design of this was rod-shaped gold nanoparticles, with a synthetic polymer tether connecting the sugars. The rod-shaped particles' longitudinal SPR band is very sensitive to binding changes, and at 800 nm, is not subject to interference from e.g. background media. We showed function using a recombinent spike protein (the N-terminal domain specifically) and also using primary swab samples.
Phage Cryopreservation Published.
With our partners at Cytivia (who host Prof Gibson as a Royal Society Industry fellow) and the Sagona Group (School of life sciences) we have investigated how polymers can be used to cryopreserve bacteriophages. Methods to freeze cells have attracted huge interest of late, for application in cell based therapies and biotechnology.We have, for example, developed macromolecular cryoprotectants which can control ice growth/formation and/or protect cells during freezing. However, virus storage is less explored. Viruses are essential from as vaccines, to vectors to engineer cells. Bacteriophages (phage) are specific bacterial viruses and several are used already to remove bacterial infections and they may have application in the future as therapies, or diagnostics. In this work, we observed (surprisingly) that just adding a small amount of PEG (poly(ethyleneglycol) protected phage during several freeze/thaw cycles at both -80 and -20 C. The mechanism of this was not clear, but ice growth (and its inhibition) was ruled out. We are continuing to study this, and to evaluate the use of polymers in many cryopreservation scenarios.
Read the paper here
Lateral Flow Glyco-Assay Demonstration of Concept Published
With our partners Iceni Diagnostics, we have been exploring lateral flow diagnostics (LFDs), and in particular replacing the need for antibodies with glycans and polymers. We have previously demonstrated that glycans can be used for detection, and in a flow-through device but we had not constructed a complete device with glycans on the stationary phase (the paper) AND mobile phase (gold nanoparticles). Our latest work, published in Advanced Healthcare Materials, shows a proof of concept that a 'lateral flow glyco assay', where only glycans are used for detection is possible. We fine-tune the polymer linkers and nanoparticle size, showing how these can modulate the signal outputs, without needing to tune the 'binder' (the glycan) - this is a significant benefit, when trying to ensure devices are selective. We show this using two lectins (carbohydrate binding proteins) and assemble complete devices for lectin detection. We think this has huge potential spanning pandemic preparedness to tools for fundamental glycoscience.
Read the paper here
Polymeric-Test Line for Lateral Flow Devices Published
Our latest work into how we can re-engineer lateral flow tests with polymeric components is published! Lateral flow tests (LFDs) are widely used for home pregnancy tests, to monitor the spread of COVID-19. A typical LFD uses antibodies on a gold nanoparticle (which makes the red colour) and forms a 'sandwich' with the analyte and another anti-body immobilised onto the paper-surface of the device. We have recently shown how synthetic polymers can be used on the gold nanoparticle surface to anchor targetting ligands which are not antibodies (e.g. glycans). In this work we explored using polymers to immobilise onto the test line (i.e. onto the paper). The current methods to immobilise non-antibody ligands is to chemically conjugate ligands onto polymeric carriers, which is non-trivial. We show here that poly(vinyl pyrrolidone) can be immobilised onto the paper, due to its ability to be dissolved in water (essential for printing) but being sufficiently hydrophobic to be retained. We install biotin and N-acetyl galactosamine as model capture units, showing that the PVP test line can be used. This is the first step towards making a robust and versatile polymeric capture agent to expand the scope of LFDs beyond antibodies.
Read the paper here:
End-Functionalized Poly(Vinyl Pyrrolidone) for Ligand Display in Lateral Flow Device Test Lines
COVID-19 detection in a rapid glycan-based diagnostic device
Our latest work, investigating SARS-COV-2 glycan interactions, and translation to diagnostic technology has been published in ACS sensors. Last year we discovered that the SARS-COV-2 spike protein could bind sialic acids (glycans found on cell surfaces and in the respiratory tract) using our glyconanoparticle platform. With our partners at Iceni Diagnostics and UHCW (Coventry Hospital) we integrated this into a flow-through device - similar to a lateral flow device - where the sample is dried, rather than captured on a test line. Using this, we show that primary swab samples of positive/negative patients can be identified correctly by this technology, and demonstrating the principle that rapid (eg lateral flow) devices that currently use antibodies as the detection agents, can be modified to use glycans instead. We also show that the spike proteins from variants of concern can still be detected in this format. Whilst still a prototype and this shows that glycan recognition can be deployed for infection monitoring and we are actively pursuing this technology.
Read the paper here; <span class="hlFld-Title">Glycan-Based Flow-Through Device for the Detection of SARS-COV-2</span>
Press release here. https://warwick.ac.uk/newsandevents/pressreleases/alternative_to_antibodies
Selectively targetting cancerous cells with nanoparticles by glycan metabolic labelling
We have a large program to explore the use of glycans for sensing and delivery applications. All mammalian cells are covered with glycans (the glycocalyx) which is responsible for a huge range of roles, from signalling to sites for pathogen-binding. We have previously explored how we can use metabolic oligosaccharide engineering to install non-natural glycans (sugars) onto cell surfaces, allowing us to 'do chemistry' on the cell surface in a bio-orthogonal manner. In this work, led by Prof Ben Boyd (Monash University), we explore how different cell types take up and display a cyclo-alkene (suitable for 'click' chemistry) bearing glycan, and use these differences to capture nanoparticles (with azides) onto the surface of the cells, leading to internalisation. Cells with the fastest growth rate processed the glycan faster, and hence lead to more nanoparticle capture. As cancerous cells are often characterized by increased metabolic rates, this may offer an opportunity to improve the targetting of nano-therapeutics by the highly selective formation of a covalent bond, rather than relying on unspecific physicochemical properties or targetting ligands.
Read the work here!