Publications

Journal article

Xu Z, Seddon JM, Beales PA, Rappolt M, Tyler AIIet al., 2021,

Breaking Isolation to Form New Networks: pH-Triggered Changes in Connectivity inside Lipid Nanoparticles

, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 143, Pages: 16556-16565, ISSN: 0002-7863

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Citations: 10

Journal article

Lucey M, Ashik T, Marzook A, Wang Y, Goulding J, Oishi A, Broichhagen J, Hodson D, Minnion J, Elani Y, Jockers R, Briddon S, Bloom S, Tomas A, Jones Bet al., 2021,

Acylation of the incretin peptide exendin-4 directly impacts GLP-1 receptor signalling and trafficking

, Molecular Pharmacology, Vol: 100, Pages: 319-334, ISSN: 0026-895X

The glucagon-like peptide-1 receptor (GLP-1R) is a class B G protein-coupled receptor and mainstay therapeutic target for the treatment of type 2 diabetes and obesity. Recent reports have highlighted how biased agonism at the GLP-1R affects sustained glucose-stimulated insulin secretion through avoidance of desensitisation and downregulation. A number of GLP-1R agonists (GLP-1RAs) feature a fatty acid moiety to prolong their pharmacokinetics via increased albumin binding, but the potential for these chemical changes to influence GLP-1R function has rarely been investigated beyond potency assessments for cyclic adenosine monophosphate (cAMP). Here we directly compare the prototypical GLP-1RA exendin-4 with its C-terminally acylated analogue, exendin-4-C16. We examine relative propensities of each ligand to recruit and activate G proteins and β-arrestins, endocytic and post-endocytic trafficking profiles, and interactions with model and cellular membranes in HEK293 and HEK293T cells. Both ligands had similar cAMP potency but exendin-4-C16 showed ~2.5-fold bias towards G protein recruitment and a ~60% reduction in β-arrestin-2 recruitment efficacy compared to exendin-4, as well as reduced GLP-1R endocytosis and preferential targeting towards recycling pathways. These effects were associated with reduced movement of the GLP-1R extracellular domain measured using a conformational biosensor approach, and a ~70% increase in insulin secretion in INS-1 832/3 cells. Interactions with plasma membrane lipids were enhanced by the acyl chain. Exendin-4-C16 showed extensive albumin binding and was highly effective for lowering of blood glucose in mice over at least 72 hours. Our study highlights the importance of a broad approach to the evaluation of GLP-1RA pharmacology.

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Journal article

Mora NL, Findlay HE, Brooks NJ, Purushothaman S, Ces O, Booth PJet al., 2021,

The membrane transporter lactose permease increases lipid bilayer bending rigidity

, BIOPHYSICAL JOURNAL, Vol: 120, Pages: 3787-3794, ISSN: 0006-3495

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Citations: 3

Journal article

Ip T, Li Q, Brooks N, Elani Yet al., 2021,

Manufacture of multilayered artificial cell membranes through sequential bilayer deposition on emulsion templates.

, ChemBioChem: a European journal of chemical biology, Vol: 22, Pages: 2275-2281, ISSN: 1439-4227

Efforts to manufacture artificial cells that replicate the architectures, processes and behaviours of biological cells are rapidly increasing. Perhaps the most commonly reconstructed cellular structure is the membrane, through the use of unilamellar vesicles as models. However, many cellular membranes, including bacterial double membranes, nuclear envelopes, and organelle membranes, are multilamellar. Due to a lack of technologies available for their controlled construction, multilayered membranes are not part of the repertoire of cell-mimetic motifs used in bottom-up synthetic biology. To address this, we developed emulsion-based technologies that allow cell-sized multilayered vesicles to be produced layer-by-layer, with compositional control over each layer, thus enabling studies that would otherwise remain inaccessible. We discovered that bending rigidities scale with the number of layers and demonstrate inter-bilayer registration between coexisting liquid-liquid domains. These technologies will contribute to the exploitation of multilayered membrane structures, paving the way for incorporating protein complexes that span multiple bilayers.

Journal article

Ip T, Li Q, Brooks N, Elani Yet al., 2021,

Front Cover: Manufacture of Multilayered Artificial Cell Membranes through Sequential Bilayer Deposition on Emulsion Templates (ChemBioChem 13/2021)

, ChemBioChem, Vol: 22, Pages: 2182-2182, ISSN: 1439-4227

Journal article

Allen ME, Elani Y, Brooks NJ, Seddon Jet al., 2021,

The effect of headgroup methylation on polymorphic phase behaviour in hydrated N-methylated phosphoethanolamine: palmitic acid membranes

, Soft Matter, Vol: 17, Pages: 5763-5771, ISSN: 1744-683X

Mixtures of fatty acids and phospholipids can form hexagonal (HII) and inverse bicontinuous cubic phases, the latter of which are implicated in various cellular processes and have wide-ranging biotechnological applications in protein crystallisation and drug delivery systems. Therefore, it is vitally important to understand the formation conditions of inverse bicontinuous cubic phases and how their properties can be tuned. We have used differential scanning calorimetry and synchrotron-based small angle and wide angle X-ray scattering (SAXS/WAXS) to investigate the polymorphic phase behaviour of palmitic acid/ partially-methylated phospholipid mixtures, and how headgroup methylation impacts on inverse bicontinuous cubic phase formation. We find that upon partial methylation of the phospholipid headgroup (1 or 2 methyl substituents) inverse bicontinuous cubic phases are formed (of the Im3m spacegroup), which is not the case with 0 or 3 methyl substituents. This shows how important headgroup methylation is for controlling phase behaviour and how a change in headgroup methylation can be used to controllably tune various inverse bicontinuous phase features such as their lattice parameter and the temperature range of their stability.

Journal article

Salvador-Castell M, Brooks NJ, Winter R, Peters J, Oger PMet al., 2021,

Non-polar lipids as regulators of membrane properties in archaeal lipid bilayer mimics

, International Journal of Molecular Sciences, Vol: 22, Pages: 6087-6087, ISSN: 1422-0067

The modification of archaeal lipid bilayer properties by the insertion of apolar molecules in the lipid bilayer midplane has been proposed to support cell membrane adaptation to extreme environmental conditions of temperature and hydrostatic pressure. In this work, we characterize the insertion effects of the apolar polyisoprenoid squalane on the permeability and fluidity of archaeal model membrane bilayers, composed of lipid analogues. We have monitored large molecule and proton permeability and Laurdan generalized polarization from lipid vesicles as a function of temperature and hydrostatic pressure. Even at low concentration, squalane (1 mol%) is able to enhance solute permeation by increasing membrane fluidity, but at the same time, to decrease proton permeability of the lipid bilayer. The squalane physicochemical impact on membrane properties are congruent with a possible role of apolar intercalants on the adaptation of Archaea to extreme conditions. In addition, such intercalant might be used to cheaply create or modify chemically resistant liposomes (archeaosomes) for drug delivery.

Journal article

Chatzimichail S, Supramaniam P, Salehi-Reyhani SA, 2021,

Absolute quantification of protein copy number in single cells with immunofluorescence microscopy calibrated using single molecule microarrays

, Analytical Chemistry, Vol: 93, Pages: 6656-6664, ISSN: 0003-2700

Great strides toward routine single cell analyses have been made over the last decade, particularly in the field of transcriptomics. For proteomics, amplification is not currently possible and has necessitated the development of ultra-sensitive platforms capable of performing such analyses on single cells. These platforms are improving in terms of throughput and multiplexability but still fall short in relation to more established methods such as fluorescence microscopy. However, microscopy methods rely on fluorescence intensity as a proxy for protein abundance and are not currently capable of reporting this in terms of absolute copy number. Here, a microfluidic implementation of single molecule microarrays for single cell analysis is assessed in its ability to calibrate fluorescence microscopy data. We show that the equivalence of measurements of the steady-state distribution of protein abundance to single molecule microarray data can be exploited to pave the way for absolute quantitation by fluorescence and immunofluorescence microscopy. The methods presented have been developed using GFP but are extendable to other proteins and other biomolecules of interest.

Journal article

Seligman H, Zaman S, Pitcher DS, Shun-Shin MJ, Hepworth Lloyd F, Androschuk V, Sen S, Al-Lamee R, Miller DM, Barnett HW, Haji GS, Howard LS, Nijjer S, Mayet J, Francis DP, Ces O, Linton NWF, Peters NS, Petraco Ret al., 2021,

Reusable snorkel masks adapted as particulate respirators

, PLoS One, Vol: 16, Pages: 1-11, ISSN: 1932-6203

ntroductionDuring viral pandemics, filtering facepiece (FFP) masks together with eye protection form the essential components of personal protective equipment (PPE) for healthcare workers. There remain concerns regarding insufficient global supply and imperfect protection offered by currently available PPE strategies. A range of full-face snorkel masks were adapted to accept high grade medical respiratory filters using bespoke-designed 3D-printed connectors. We compared the protection offered by the snorkel to that of standard PPE using a placebo-controlled respirator filtering test as well as a fluorescent droplet deposition experiment. Out of the 56 subjects tested, 42 (75%) passed filtering testing with the snorkel mask compared to 31 (55%) with a FFP3 respirator mask (p = 0.003). Amongst the 43 subjects who were not excluded following a placebo control, 85% passed filtering testing with the snorkel versus to 68% with a FFP3 mask (p = 0.008). Following front and lateral spray of fluorescence liquid particles, the snorkel mask also provided superior protection against droplet deposition within the subject’s face, when compared to a standard PPE combination of FFP3 masks and eye protection (3.19x108 versus 6.81x108 fluorescence units, p<0.001). The 3D printable adaptors are available for free download online at https://www.ImperialHackspace.com/COVID-19-Snorkel-Respirator-Project/.ConclusionFull-face snorkel masks adapted as particulate respirators performed better than a standard PPE combination of FFP3 mask and eye protection against aerosol inhalation and droplet deposition. This adaptation is therefore a promising PPE solution for healthcare workers during highly contagious viral outbreaks.

Journal article

Zhang S, Contini C, Hindley J, Bolognesi G, Elani Y, Ces Oet al., 2021,

Engineering motile aqueous phase-separated droplets via liposome stabilisation

, Nature Communications, Vol: 12, Pages: 1-11, ISSN: 2041-1723

There are increasing efforts to engineer functional compartments that mimic cellular behaviours from the bottom-up. One behaviour that is receiving particular attention is motility, due to its biotechnological potential and ubiquity in living systems. Many existing platforms make use of the Marangoni effect to achieve motion in water/oil (w/o) droplet systems. However, most of these systems are unsuitable for biological applications due to biocompatibility issues caused by the presence of oil phases. Here we report a biocompatible all aqueous (w/w) PEG/dextran Pickering-like emulsion system consisting of liposome-stabilised cell-sized droplets, where the stability can be easily tuned by adjusting liposome composition and concentration. We demonstrate that the compartments are capable of negative chemotaxis: these droplets can respond to a PEG/dextran polymer gradient through directional motion down to the gradient. The biocompatibility, motility and partitioning abilities of this droplet system offers new directions to pursue research in motion-related biological processes.

Journal article

Elani Y, 2021,

Interfacing living and synthetic cells as an emerging frontier in synthetic biology

, Angewandte Chemie International Edition, Vol: 60, Pages: 5602-5611, ISSN: 1433-7851

The construction of artificial cells from inanimate molecular building blocks is one of the grand challenges of our time. In addition to being used as simplified cell models to decipher the rules of life, artificial cells have the potential to be designed as micromachines deployed in a host of clinical and industrial applications. The attractions of engineering artificial cells from scratch, as opposed to re‐engineering living biological cells, are varied. However, it is clear that artificial cells cannot currently match the power and behavioural sophistication of their biological counterparts. Given this, many in the synthetic biology community have started to ask: is it possible to interface biological and artificial cells together to create hybrid living/synthetic systems that leverage the advantages of both? This article will discuss the motivation behind this cellular bionics approach, in which the boundaries between living and non‐living matter are blurred by bridging top‐down and bottom‐up synthetic biology. It details the state of play of this nascent field and introduces three generalised hybridisation modes that have emerged.

Journal article

Elani Y, 2021,

Interfacing Living and Synthetic Cells as an Emerging Frontier in Synthetic Biology.

, Angew Chem Weinheim Bergstr Ger, Vol: 133, Pages: 5662-5671, ISSN: 0044-8249

The construction of artificial cells from inanimate molecular building blocks is one of the grand challenges of our time. In addition to being used as simplified cell models to decipher the rules of life, artificial cells have the potential to be designed as micromachines deployed in a host of clinical and industrial applications. The attractions of engineering artificial cells from scratch, as opposed to re-engineering living biological cells, are varied. However, it is clear that artificial cells cannot currently match the power and behavioural sophistication of their biological counterparts. Given this, many in the synthetic biology community have started to ask: is it possible to interface biological and artificial cells together to create hybrid living/synthetic systems that leverage the advantages of both? This article will discuss the motivation behind this cellular bionics approach, in which the boundaries between living and non-living matter are blurred by bridging top-down and bottom-up synthetic biology. It details the state of play of this nascent field and introduces three generalised hybridisation modes that have emerged.

Journal article

Paez-Perez M, Lopez-Duarte I, Vysniauskas A, Brooks NJ, Kuimova MKet al., 2021,

Imaging non-classical mechanical responses of lipid membranes using molecular rotors

, Chemical Science, Vol: 12, Pages: 2604-2613, ISSN: 2041-6520

Lipid packing in cellular membranes has a direct effect on membrane tension and microviscosity, and plays a central role in cellular adaptation, homeostasis and disease. According to conventional mechanical descriptions, viscosity and tension are directly interconnected, with increased tension leading to decreased membrane microviscosity. However, the intricate molecular interactions that combine to build the structure and function of a cell membrane suggest a more complex relationship between these parameters. In this work, a viscosity-sensitive fluorophore (‘molecular rotor’) is used to map changes in microviscosity in model membranes under conditions of osmotic stress. Our results suggest that the relationship between membrane tension and microviscosity is strongly influenced by the bilayer's lipid composition. In particular, we show that the effects of increasing tension are minimised for membranes that exhibit liquid disordered (Ld) – liquid ordered (Lo) phase coexistence; while, surprisingly, membranes in pure gel and Lo phases exhibit a negative compressibility behaviour, i.e. they soften upon compression.

Journal article

Pilkington CP, Seddon JM, Elani Y, 2021,

Microfluidic technologies for the synthesis and manipulation of biomimetic membranous nano-assemblies.

, Physical Chemistry Chemical Physics, Vol: 23, Pages: 3693-3706, ISSN: 1463-9076

Microfluidics has been proposed as an attractive alternative to conventional bulk methods used in the generation of self-assembled biomimetic structures, particularly where there is a desire for more scalable production. The approach also allows for greater control over the self-assembly process, and parameters such as particle architecture, size, and composition can be finely tuned. Microfluidic techniques used in the generation of microscale assemblies (giant vesicles and higher-order multi-compartment assemblies) are fairly well established. These tend to rely on microdroplet templation, and the resulting structures have found use as comparmentalised motifs in artificial cells. Challenges in generating sub-micron droplets have meant that reconfiguring this approach to form nano-scale structures is not straightforward. This is beginning to change however, and recent technological advances have instigated the manufacture and manipulation of an increasingly diverse repertoire of biomimetic nano-assemblies, including liposomes, polymersomes, hybrid particles, multi-lamellar structures, cubosomes, hexosomes, nanodiscs, and virus-like particles. The following review will discuss these higher-order self-assembled nanostructures, including their biochemical and industrial applications, and techniques used in their production and analysis. We suggest ways in which existing technologies could be repurposed for the enhanced design, manufacture, and exploitation of these structures and discuss potential challenges and future research directions. By compiling recent advances in this area, it is hoped we will inspire future efforts toward establishing scalable microfluidic platforms for the generation of biomimetic nanoparticles of enhanced architectural and functional complexity.

Journal article

Chatzimichail S, Rahimi F, Saifuddin A, Surman A, Taylor-Robinson S, Salehi-Reyhani SAet al., 2021,

Hand-portable HPLC with broadband spectral detection enables analysis of complex polycyclic aromatic hydrocarbon mixtures

, Communications Chemistry, Vol: 4, ISSN: 2399-3669

Polycyclic aromatic hydrocarbons (PAHs) are considered priority hazardous substances due to their carcinogenic activity and risk to public health. Strict regulations are in place limiting their release into the environment, but enforcement is hampered by a lack of adequate field-testing procedure, instead relying on sending samples to centralised analytical facilities. Reliably monitoring levels of PAHs in the field is a challenge, owing to the lack of field-deployable analytical methods able to separate, identify, and quantify the complex mixtures in which PAHs are typically observed. Here, we report the development of a hand-portable system based on high-performance liquid chromatography incorporating a spectrally wide absorption detector, capable of fingerprinting PAHs based on their characteristic spectral absorption profiles: identifying 100% of the 24 PAHs tested, including full coverage of the United States Environmental Protection Agency priority pollutant list. We report unsupervised methods to exploit these new capabilities for feature detection and identification, robust enough to detect and classify co-eluting and hidden peaks. Identification is fully independent of their characteristic retention times, mitigating matrix effects which can preclude reliable determination of these analytes in challenging samples. We anticipate the platform to enable more sophisticated analytical measurements, supporting real-time decision making in the field.

Journal article

Strutt R, Hindley JW, Gregg J, Booth PJ, Harling JD, Law RV, Friddin MS, Ces Oet al., 2021,

Activating mechanosensitive channels embedded in droplet interface bilayers using membrane asymmetry

, Chemical Science, Vol: 12, Pages: 2138-2145, ISSN: 2041-6520

Droplet microcompartments linked by lipid bilayers show great promise in the construction of synthetic minimal tissues. Central to controlling the flow of information in these systems are membrane proteins, which can gate in response to specific stimuli in order to control the molecular flux between membrane separated compartments. This has been demonstrated with droplet interface bilayers (DIBs) using several different membrane proteins combined with electrical, mechanical, and/or chemical activators. Here we report the activation of the bacterial mechanosensitive channel of large conductance (MscL) in a dioleoylphosphatidylcholine:dioleoylphosphatidylglycerol DIB by controlling membrane asymmetry. We show using electrical measurements that the incorporation of lysophosphatidylcholine (LPC) into one of the bilayer leaflets triggers MscL gating in a concentration-dependent manner, with partial and full activation observed at 10 and 15 mol% LPC respectively. Our findings could inspire the design of new minimal tissues where flux pathways are dynamically defined by lipid composition.

Journal article

Heide C, Buldum G, Moya-Ramirez I, Ces O, Kontoravdi K, Polizzi Ket al., 2021,

Design, development and optimisation of a functional mammalian cell-free protein synthesis platform

, Frontiers in Bioengineering and Biotechnology, Vol: 8, ISSN: 2296-4185

In this paper, we describe the stepwise development of a cell-free protein synthesis (CFPS) platform derived from cultured Chinese hamster ovary (CHO) cells. We provide a retrospective summary of the design challenges we faced, and the optimized methods developed for the cultivation of cells and the preparation of translationally active lysates. To overcome low yields, we developed procedures to supplement two accessory proteins, GADD34 and K3L, into the reaction to prevent deactivation of the translational machinery by phosphorylation. We compared different strategies for implementing these accessory proteins including two variants of the GADD34 protein to understand the potential trade-offs between yield and ease of implementation. Addition of the accessory proteins increased yield of turbo Green Fluorescent Protein (tGFP) by up to 100-fold depending on which workflow was used. Using our optimized protocols as a guideline, users can successfully develop their own functional CHO CFPS system, allowing for broader application of mammalian CFPS.

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Book chapter

Conn CE, Seddon JM, 2021,

Structures of Lipid Membranes: Cubic and Inverse Hexagonal Phases

, Handbook of Lipid Membranes Molecular Functional and Materials Aspects, Pages: 49-64

Non-lamellar phases of lipids are of interest due to their relevance to understanding the driving forces behind curvature and topological transformations in biomembranes. In addition, they have a great potential in applications such as drug or gene delivery to cells. In this chapter, the interactions driving the formation of phases having curved interfaces are first briefly reviewed, leading to a description of the underlying engineering design principles for producing a given lipid phase. For biomedical applications, it is generally necessary to disperse the bulk lipid phases in the form of nanoparticles (cubosomes or hexosomes). The role of hydrostatic pressure in controlling lipid phase behaviour is poorly understood and yet is of great importance, for example in marine biology. In vivo there is increasing evidence that cubic phases carry out specific functions in a variety of species and also play a role during fat digestion. Finally, the use of lipid cubic phases for the crystallization of membrane proteins is discussed.

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Journal article

Potter M, Najer A, Kloeckner A, Zhang S, Holme MN, Nele V, Che J, Penders J, Saunders C, Doutch JJ, Edwards A, Ces O, Stevens Met al., 2020,

Controlled dendrimersome nanoreactor system for localised hypochlorite-induced killing of bacteria

, ACS Nano, Vol: 14, Pages: 17333-17353, ISSN: 1936-0851

Antibiotic resistance is a serious global health problem necessitating new bactericidal approaches such as nanomedicines. Dendrimersomes (DSs) have recently become a valuable alternative nanocarrier to polymersomes and liposomes due to their molecular definition and synthetic versatility. Despite this, their biomedical application is still in its infancy. Inspired by the localized antimicrobial function of neutrophil phagosomes and the versatility of DSs, a simple three-component DS-based nanoreactor with broad-spectrum bactericidal activity is presented. This was achieved by encapsulation of glucose oxidase (GOX) and myeloperoxidase (MPO) within DSs (GOX-MPO-DSs), self-assembled from an amphiphilic Janus dendrimer, that possesses a semipermeable membrane. By external addition of glucose to GOX-MPO-DS, the production of hypochlorite (−OCl), a highly potent antimicrobial, by the enzymatic cascade was demonstrated. This cascade nanoreactor yielded a potent bactericidal effect against two important multidrug resistant pathogens, Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa), not observed for H2O2 producing nanoreactors, GOX-DS. The production of highly reactive species such as –OCl represents a harsh bactericidal approach that could also be cytotoxic to mammalian cells. This necessitates the development of strategies for activating –OCl production in a localized manner in response to a bacterial stimulus. One option of locally releasing sufficient amounts of substrate using a bacterial trigger (released toxins) was demonstrated with lipidic glucose-loaded giant unilamellar vesicles (GUVs), envisioning, e.g., implant surface modification with nanoreactors and GUVs for localized production of bactericidal agents in the presence of bacterial growth.

Journal article

Shimolina LE, Gulin AA, Paez-Perez M, Lopez-Duarte I, Druzhkova IN, Lukina MM, Gubina M, Brooks NJ, Zagaynova E, Kuimova MK, Shirmanova Met al., 2020,

Mapping cisplatin-induced viscosity alterations in cancer cells using molecular rotor and fluorescence lifetime imaging microscopy

, Journal of Biomedical Optics, Vol: 25, Pages: 1-16, ISSN: 1083-3668

Significance: Despite the importance of the cell membrane in regulation of drug activity, the influence of drug treatments on its physical properties is still poorly understood. The combination of fluorescence lifetime imaging microscopy (FLIM) with specific viscosity-sensitive fluorescent molecular rotors allows the quantification of membrane viscosity with high spatiotemporal resolution, down to the individual cell organelles.Aim: The aim of our work was to analyze microviscosity of the plasma membrane of living cancer cells during chemotherapy with cisplatin using FLIM and correlate the observed changes with lipid composition and cell’s response to treatment.Approach: FLIM together with viscosity-sensitive boron dipyrromethene-based fluorescent molecular rotor was used to map the fluidity of the cell’s membrane. Chemical analysis of membrane lipid composition was performed with time-of-flight secondary ion mass spectrometry (ToF-SIMS).Results: We detected a significant steady increase in membrane viscosity in viable cancer cells, both in cell monolayers and tumor spheroids, upon prolonged treatment with cisplatin, as well as in cisplatin-adapted cell line. ToF-SIMS revealed correlative changes in lipid profile of cisplatin-treated cells.Conclusions: These results suggest an involvement of membrane viscosity in the cell adaptation to the drug and in the acquisition of drug resistance.

Journal article

Rowlands LJ, Marks A, Sanderson JM, Law Ret al., 2020,

<SUP>17</SUP>O NMR spectroscopy as a tool to study hydrogen bonding of cholesterol in lipid bilayers

, CHEMICAL COMMUNICATIONS, Vol: 56, Pages: 14499-14502, ISSN: 1359-7345

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Citations: 15

Journal article

Contini C, Hindley J, Macdonald T, Barritt J, Ces O, Quirke Net al., 2020,

Size dependency of gold nanoparticles interacting with model membranes

, Communications Chemistry, Vol: 3, Pages: 1-12, ISSN: 2399-3669

The rapid development of nanotechnology has led to an increase in the number and variety of engineered nanomaterials in the environment. Gold nanoparticles (AuNPs) are an example of a commonly studied nanomaterial whose highly tailorable properties have generated significant interest through a wide range of research fields. In the present work, we characterise the AuNP-lipid membrane interaction by coupling qualitative data with quantitative measurements of the enthalpy change of interaction. We investigate the interactions between citrate-stabilised AuNPs ranging from 5 to 60 nm in diameter and large unilamellar vesicles acting as a model membrane system. Our results reveal the existence of two critical AuNP diameters which determine their fate when in contact with a lipid membrane. The results provide new insights into the size dependent interaction between AuNPs and lipid bilayers which is of direct relevance to nanotoxicology and to the design of NP vectors.

Journal article

Rahimi F, Chatzimichail S, Saifuddin A, Surman A, Taylor-Robinson S, Salehi-Reyhani SAet al., 2020,

A review of portable high-performance liquid chromatography: the future of the field?

, Chromatographia, Vol: 83, Pages: 1165-1195, ISSN: 0009-5893

There is a growing need for chemical analyses to be performed in the field, at the point of need. Tools and techniques often found in analytical chemistry laboratories are necessary in performing these analyses, yet have, historically, been unable to do so owing to their size, cost and complexity. Technical advances in miniaturisation and liquid chromatography are enabling the translation of these techniques out of the laboratory, and into the field. Here we examine the advances that are enabling portable liquid chromatography (LC). We explore the evolution of portable instrumentation from its inception to the most recent advances, highlighting the trends in the field and discussing the necessary criteria for developing in-field solutions. While instrumentation is becoming more capable it has yet to find adoption outside of research.

Working paper

Zhang S, Contini C, Hindley J, Bolognesi G, Elani Y, Ces Oet al., 2020,

Engineering motile aqueous phase-separated droplets via liposome stabilisation

<title>Abstract</title> <p>There are increasing efforts to engineer functional compartments that mimic aspects of cellular behaviour in a drive to construct an artificial cell from the bottom-up. One behaviour that is receiving particular attention is motility, due to its biotechnological potential and the fact that movement of discrete cells is a ubiquitous feature of living systems. Many existing platforms make use of the Marangoni effect to achieve motion in water/oil (w/o) droplet systems. However, most of these systems are unsuitable for biological applications due to issues with biocompatibility caused by the presence of oil phases. Here we report a biocompatible all aqueous (w/w) PEG/dextran Pickering-like emulsion system consisting of liposome-stabilized cell-sized droplets, where the stability can be easily tuned by adjusting liposome composition and concentration. We demonstrate that the compartments are capable of negative chemotaxis: if water is introduced into the emulsion system, these droplets can respond through directional motion away from PEG in the continuous phase and down to the polymer gradient with a velocity change proportional to the rearrangement of liposome stabilisers in the PEG/dextran interface. The biocompatibility, motility and partitioning abilities of this novel droplet system offers new directions to pursue research in motion-related biological processes.</p>

Journal article

Carter JW, Gonzalez MA, Brooks NJ, Seddon JM, Bresme Fet al., 2020,

Flip-flop asymmetry of cholesterol in model membranes induced by thermal gradients

, Soft Matter, Vol: 16, Pages: 5925-5932, ISSN: 1744-683X

Lipid asymmetry is a crucial property of biological membranes and significantly influences their physical and mechanical properties. It is responsible for maintaining different chemical environments on the external and internal surfaces of cells and organelles and plays a vital role in many biological processes such as cell signalling and budding. In this work we show, using non-equilibrium molecular dynamics (NEMD) simulations, that thermal fields can induce lipid asymmetry in biological membranes. We focus our investigation on cholesterol, an abundant lipid in the plasma membrane, with a rapid flip-flop rate, significantly influencing membrane properties. We demonstrate that thermal fields induce membrane asymmetry with cholesterol showing thermophobic behaviour and therefore accumulating on the cold side of the membrane. This work highlights a possible experimental route to preparing and controlling asymmetry in synthetic membranes.

Journal article

Mann SK, Devgan MK, Franks WT, Huband S, Chan CL, Griffith J, Pugh D, Brooks NJ, Welton T, Pham TN, McQueen LL, Lewandowski JR, Brown SPet al., 2020,

MAS NMR Investigation of Molecular Order in an Ionic Liquid Crystal

, JOURNAL OF PHYSICAL CHEMISTRY B, Vol: 124, Pages: 4975-4988, ISSN: 1520-6106

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Citations: 14

Journal article

Haylock S, Friddin M, Hindley J, Rodriguez E, Charalambous K, Booth P, Barter L, Ces Oet al., 2020,

Membrane protein mediated bilayer communication in networks of droplet interface bilayers

, Communications Chemistry, Vol: 3, ISSN: 2399-3669

Droplet interface bilayers (DIBs) are model membranes formed between lipid monolayer-encased water droplets in oil. Compared to conventional methods, one of the most unique properties of DIBs is that they can be connected together to generate multi-layered ‘tissue-like’ networks, however introducing communication pathways between these compartments typically relies on water-soluble pores that are unable to gate. Here, we show that network connectivity can instead be achieved using a water-insoluble membrane protein by successfully reconstituting a chemically activatable mutant of the mechanosensitive channel MscL into a network of DIBs. Moreover, we also show how the small molecule activator can diffuse through an open channel and across the neighbouring droplet to activate MscL present in an adjacent bilayer. This demonstration of membrane protein mediated bilayer communication could prove key toward developing the next generation of responsive bilayer networks capable of defining information flow inside a minimal tissue.

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Journal article

Weatherby S, Seddon JM, Ceroni P, 2020,

Luminescent silicon nanostructures and COVID-19

, FARADAY DISCUSSIONS, Vol: 222, Pages: 8-9, ISSN: 1359-6640

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Citations: 3

Journal article

Tascini AS, Wang S, Seddon JM, Bresme F, Chen Ret al., 2020,

Fats’ love–hate relationships: a molecular dynamics simulation and hands-on experiment outreach activity to introduce the amphiphilic nature and biological functions of lipids to young students and the general public

, Journal of Chemical Education, Vol: 97, Pages: 1360-1367, ISSN: 0021-9584

Lipids are fundamental components of biological organisms and have important applications in the pharmaceutical, food, and cosmetics industries. Thus, it is important that young students and the general public properly understand the basic properties of lipids and how these relate to their biological and industrial roles. Here, we use molecular dynamics computer simulations and a simple, safe, and inexpensive popular hands-on activity, to communicate to participants why and how lipid molecules play a fundamental role in all living organisms and in our bodies. The activity is called “Fats’ Love–Hate Relationships”, to highlight how the different parts of amphiphilic lipids interact with water. This “love–hate relationship” is vital to the biological functions of lipids and drives the formation of lipid structures that can be visualized at molecular scale with the computer simulations. The participants were encouraged to investigate the interactions between milk lipids and soap surfactants, creating beautiful complex artwork that they could then take home. The hands-on activity was accompanied by a video of a molecular simulation that illustrates milk–soap interactions at a molecular scale and helps to explain how the amphiphilicity of lipids creates the beautiful artwork at a molecular level. The outreach activity has been performed in science festivals and in classrooms and has been well received by participants of all ages with multiple learner comprehension levels (primary and secondary school students and the general public). By combining molecular simulation, explanations of the amphiphilic structure of the lipids, and an engaging hands-on activity, we explained how lipids interact with water and surfactants and inspired discussions on the link between the structure of the lipids and their biological function, namely, their structural and protective roles as a key component of cell membranes.

Journal article

Hindley JW, Law RV, Ces O, 2020,

Membrane functionalization in artificial cell engineering

, SN Applied Sciences, Vol: 2, ISSN: 2523-3963

Bottom-up synthetic biology aims to construct mimics of cellular structure and behaviour known as artificial cells from a small number of molecular components. The development of this nascent field has coupled new insights in molecular biology with large translational potential for application in fields such as drug delivery and biosensing. Multiple approaches have been applied to create cell mimics, with many efforts focusing on phospholipid-based systems. This mini-review focuses on different approaches to incorporating molecular motifs as tools for lipid membrane functionalization in artificial cell construction. Such motifs range from synthetic chemical functional groups to components from extant biology that can be arranged in a ‘plug-and-play’ approach which is hard to replicate in living systems. Rationally designed artificial cells possess the promise of complex biomimetic behaviour from minimal, highly engineered chemical networks.

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Structures of Lipid Membranes: Cubic and Inverse Hexagonal Phases

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