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  • Journal article
    Barlow N, Kusumaatmaja H, Salehi-Reyhani A, Brooks N, Barter LMC, Flemming AJ, Ces Oet al., 2018,

    Measuring bilayer surface energy and curvature in asymmetric droplet interface bilayers

    , Journal of the Royal Society Interface, Vol: 15, ISSN: 1742-5662

    For the past decade, droplet interface bilayers (DIBs) have had an increased prevalence in biomolecular and biophysical literature. However, much of the underlying physics of these platforms is poorly characterized. To further our understanding of these structures, lipid membrane tension on DIB membranes is measured by analysing the equilibrium shape of asymmetric DIBs. To this end, the morphology of DIBs is explored for the first time using confocal laser scanning fluorescence microscopy. The experimental results confirm that, in accordance with theory, the bilayer interface of a volume-asymmetric DIB is curved towards the smaller droplet and a lipid-asymmetric DIB is curved towards the droplet with the higher monolayer surface tension. Moreover, the DIB shape can be exploited to measure complex bilayer surface energies. In this study, the bilayer surface energy of DIBs composed of lipid mixtures of phosphatidylgylcerol (PG) and phosphatidylcholine are shown to increase linearly with PG concentrations up to 25%. The assumption that DIB bilayer area can be geometrically approximated as a spherical cap base is also tested, and it is discovered that the bilayer curvature is negligible for most practical symmetric or asymmetric DIB systems with respect to bilayer area.
  • Journal article
    Girvan P, Teng X, Brooks NJ, Baldwin GS, Ying Let al., 2018,

    Redox Kinetics of the Amyloid-β-Cu Complex and Its Biological Implications

    , BIOCHEMISTRY, Vol: 57, Pages: 6228-6233, ISSN: 0006-2960
  • Journal article
    Trantidou T, Dekker L, Polizzi K, Ces O, Elani Yet al., 2018,

    Functionalizing cell-mimetic giant vesicles with encapsulated bacterial biosensors

    , Interface Focus, Vol: 8, ISSN: 2042-8901

    The design of vesicle microsystems as artificial cells (bottom-up synthetic biology) has traditionally relied on the incorporation of molecular components to impart functionality. These cell mimics have reduced capabilities compared with their engineered biological counterparts (top-down synthetic biology), as they lack the powerful metabolic and regulatory pathways associated with living systems. There is increasing scope for using whole intact cellular components as functional modules within artificial cells, as a route to increase the capabilities of artificial cells. In this feasibility study, we design and embed genetically engineered microbes (Escherichia coli) in a vesicle-based cell mimic and use them as biosensing modules for real-time monitoring of lactate in the external environment. Using this conceptual framework, the functionality of other microbial devices can be conferred into vesicle microsystems in the future, bridging the gap between bottom-up and top-down synthetic biology.
  • Journal article
    Chatzimichail S, Supramaniam P, Ces O, Salehi-Reyhani Set al., 2018,

    Micropatterning of planar metal electrodes by vacuum filling microfluidic channel geometries

    , Scientific Reports, Vol: 8, ISSN: 2045-2322

    We present a simple, facile method to micropattern planar metal electrodes defined by the geometry of a microfluidic channel network template. By introducing aqueous solutions of metal into reversibly adhered PDMS devices by desiccation instead of flow, we are able to produce difficult to pattern “dead end” or discontinuous features with ease. We characterize electrodes fabricated using this method and perform electrical lysis of mammalian cancer cells and demonstrate their use as part of an antibody capture assay for GFP. Cell lysis in microwell arrays is achieved using the electrodes and the protein released is detected using an antibody microarray. We show how the template channels used as part of the workflow for patterning the electrodes may be produced using photolithography-free methods, such as laser micromachining and PDMS master moulding, and demonstrate how the use of an immiscible phase may be employed to create electrode spacings on the order of 25 – 50 μm, that overcome the current resolution limits of such methods. This work demonstrates how the rapid prototyping of electrodes for use in total analysis systems can be achieved on the bench with little or no need for centralized facilities.
  • Journal article
    Jia J, White ER, Clancy AJ, Rubio N, Suter T, Miller TS, McColl K, McMillan PF, Brázdová V, Corà F, Howard CA, Law RV, Mattevi C, Shaffer MSPet al., 2018,

    Fast exfoliation and functionalisation of two-dimensional crystalline carbon nitride by framework charging

    , Angewandte Chemie, Vol: 57, Pages: 12656-12660, ISSN: 1521-3757

    Two-dimensional (2D) layered graphitic carbon nitride (gCN) nanosheets offer intriguing electronic and chemical properties. However, the exfoliation and functionalisation of gCN for specific applications remain challenging. We report a scalable one-pot reductive method to produce solutions of single- and few-layer 2D gCN nanosheets with excellent stability in a high mass yield (35 %) from polytriazine imide. High-resolution imaging confirmed the intact crystalline structure and identified an AB stacking for gCN layers. The charge allows deliberate organic functionalisation of dissolved gCN, providing a general route to adjust their properties.
  • Journal article
    Trantidou T, Friddin M, Salehi-Reyhani S, Ces O, Elani Yet al., 2018,

    Droplet microfluidics for the construction of compartmentalised model membranes

    , Lab on a Chip, Vol: 18, Pages: 2488-2509, ISSN: 1473-0189

    The design of membrane-based constructs with multiple compartments is of increasing importance given their potential applications as microreactors, as artificial cells in synthetic-biology, as simplified cell models, and as drug delivery vehicles. The emergence of droplet microfluidics as a tool for their construction has allowed rapid scale-up in generation throughput, scale-down of size, and control over gross membrane architecture. This is true on several levels: size, level of compartmentalisation and connectivity of compartments can all be programmed to various degrees. This tutorial review explains and explores the reasons behind this. We discuss microfluidic strategies for the generation of a family of compartmentalised systems that have lipid membranes as the basic structural motifs, where droplets are either the fundamental building blocks, or are precursors to the membrane-bound compartments. We examine the key properties associated with these systems (including stability, yield, encapsulation efficiency), discuss relevant device fabrication technologies, and outline the technical challenges. In doing so, we critically review the state-of-play in this rapidly advancing field.
  • Journal article
    Holme MN, Rana S, Barriga H, Kauscher U, Brooks NJ, Stevens MMet al., 2018,

    A robust liposomal platform for direct colorimetric detection of sphingomyelinase enzyme and inhibitors

    , ACS Nano, Vol: 12, Pages: 8197-8207, ISSN: 1936-0851

    The enzyme sphingomyelinase (SMase) is an important biomarker for several diseases such as Niemann Pick’s, atherosclerosis, multiple sclerosis, and HIV. We present a two-component colorimetric SMase activity assay that is more sensitive and much faster than currently available commercial assays. Herein, SMase-triggered release of cysteine from a sphingomyelin (SM)-based liposome formulation with 60 mol % cholesterol causes gold nanoparticle (AuNP) aggregation, enabling colorimetric detection of SMase activities as low as 0.02 mU/mL, corresponding to 1.4 pM concentration. While the lipid composition offers a stable, nonleaky liposome platform with minimal background signal, high specificity toward SMase avoids cross-reactivity of other similar phospholipases. Notably, use of an SM-based liposome formulation accurately mimics the natural in vivo substrate: the cell membrane. We studied the physical rearrangement process of the lipid membrane during SMase-mediated hydrolysis of SM to ceramide using small- and wide-angle X-ray scattering. A change in lipid phase from a liquid to gel state bilayer with increasing concentration of ceramide accounts for the observed increase in membrane permeability and consequent release of encapsulated cysteine. We further demonstrated the effectiveness of the sensor in colorimetric screening of small-molecule drug candidates, paving the way for the identification of novel SMase inhibitors in minutes. Taken together, the simplicity, speed, sensitivity, and naked-eye readout of this assay offer huge potential in point-of-care diagnostics and high-throughput drug screening.
  • Journal article
    Brooker HR, Gyamfi IA, Wieckowska A, Brooks NJ, Mulvihill DP, Geeves MAet al., 2018,

    A novel live-cell imaging system reveals a reversible hydrostatic pressure impact on cell-cycle progression

    , JOURNAL OF CELL SCIENCE, Vol: 131, ISSN: 0021-9533
  • Journal article
    Chatzimichail S, Supramaniam P, Ces O, Salehi-Reyhani Set al., 2018,

    Counting proteins in single cells with addressable droplet microarrays

    , Jove-Journal of Visualized Experiments, Vol: 137, ISSN: 1940-087X

    Often cellular behaviour and cellular responses are analysed at the population level where the responses of many cells are pooled together as an average result masking the rich single cell behaviour within a complex population. Single cell protein detection and quantification technologies have made a remarkable impact in recent years. Here we describe a practical and flexible single cell analysis platform based on addressable droplet microarrays. This study describes how the absolute copy numbers of target proteins may be measured with single cell resolution. The tumour suppressor p53 is the most commonly mutated gene in human cancer, with more than 50% of total cancer cases exhibiting a non-healthy p53 expression pattern. The protocol describes steps to create 10nL droplets within which single human cancer cells are isolated and the copy number of p53 protein is measured with single molecule resolution to precisely determine the variability in expression. The method may be applied to any cell type including primary material to determine the absolute copy number of any target proteins of interest.
  • Journal article
    Bolognesi G, Friddin MS, Salehi-Reyhani S, Barlow N, Brooks NJ, Ces O, Elani Yet al., 2018,

    Sculpting and fusing biomimetic vesicle networks using optical tweezers

    , Nature Communications, Vol: 9, Pages: 1-11, ISSN: 2041-1723

    Constructing higher-order vesicle assemblies has discipline-spanning potential from responsive soft-matter materials to artificial cell networks in synthetic biology. This potential is ultimately derived from the ability to compartmentalise and order chemical species in space. To unlock such applications, spatial organisation of vesicles in relation to one another must be controlled, and techniques to deliver cargo to compartments developed. Herein, we use optical tweezers to assemble, reconfigure and dismantle networks of cell-sized vesicles that, in different experimental scenarios, we engineer to exhibit several interesting properties. Vesicles are connected through double-bilayer junctions formed via electrostatically controlled adhesion. Chemically distinct vesicles are linked across length scales, from several nanometres to hundreds of micrometres, by axon-like tethers. In the former regime, patterning membranes with proteins and nanoparticles facilitates material exchange between compartments and enables laser-triggered vesicle merging. This allows us to mix and dilute content, and to initiate protein expression by delivering biomolecular reaction components.
  • Journal article
    Karamdad K, Hindley J, Friddin MS, Bolognesi G, Law RV, Brooks NJ, Ces O, Elani Yet al., 2018,

    Engineering thermoresponsive phase separated vesicles formed via emulsion phase transfer as a content-release platform

    , Chemical Science, Vol: 9, Pages: 4851-4858, ISSN: 2041-6520

    Giant unilamellar vesicles (GUVs) are a well-established tool for the study of membrane biophysics and are increasingly used as artificial cell models and functional units in biotechnology. This trend is driven by the development of emulsion-based generation methods such as Emulsion Phase Transfer (EPT), which facilitates the encapsulation of almost any water-soluble compounds (including biomolecules) regardless of size or charge, is compatible with droplet microfluidics, and allows GUVs with asymmetric bilayers to be assembled. However, the ability to control the composition of membranes formed via EPT remains an open question; this is key as composition gives rise to an array of biophysical phenomena which can be used to add functionality to membranes. Here, we evaluate the use of GUVs constructed via this method as a platform for phase behaviour studies and take advantage of composition-dependent features to engineer thermally-responsive GUVs. For the first time, we generate ternary GUVs (DOPC/DPPC/cholesterol) using EPT, and by compensating for the lower cholesterol incorporation efficiencies, show that these possess the full range of phase behaviour displayed by electroformed GUVs. As a demonstration of the fine control afforded by this approach, we demonstrate release of dye and peptide cargo when ternary GUVs are heated through the immiscibility transition temperature, and show that release temperature can be tuned by changing vesicle composition. We show that GUVs can be individually addressed and release triggered using a laser beam. Our findings validate EPT as a suitable method for generating phase separated vesicles and provide a valuable proof-of-concept for engineering content release functionality into individually addressable vesicles, which could have a host of applications in the development of smart synthetic biosystems.
  • Journal article
    Trantidou T, Regoutz A, Voon X, Payne D, Ces Oet al., 2018,

    A “cleanroom-free” and scalable manufacturing technology for the microfluidic generation of lipid-stabilized droplets and cell-sized multisomes

    , Sensors and Actuators B: Chemical, Vol: 267, Pages: 34-41, ISSN: 0925-4005

    There is a growing demand to construct artificial biomimetic structures from the bottom-up using simple chemical components in a controlled and high-throughput way. These cell mimics are encapsulated by lipid membranes and can reconstitute biological machinery within them. To date, such synthetic cells based upon droplet microfluidics are fabricated using non-scalable, expensive and time-consuming strategies, and are thus restricted to small-scale in-house manufacturing. Here, we report a “cleanroom-free” and highly scalable microfluidic manufacturing technology based on dry film resists and multilayer lamination. The technology facilitates the controlled and high-throughput generation of stable and monodisperse droplets using anionic surfactants and more biologically relevant phospholipids. We demonstrate the versatility of this approach by selectively patterning the surface chemistry of the device, enabling the production of compartmentalized lipid structures based on droplet interface bilayers (multisomes). This technology has the potential to simultaneously unlock the widespread exploitation of microfluidics to chemists and synthetic biologists not having access to controlled production environments and facilitate low-cost (< £1) high-volume fabrication of self-contained disposable devices with minimum feature sizes of 30 μm. The associated material and equipment costs approach those of other deskilled prototyping technologies, such as 3D printing that have made the transition into the mainstream.
  • Journal article
    Slatter DA, Percy CL, Allen-Redpath K, Gajsiewicz JM, Brooks NJ, Clayton A, Tyrrell VJ, Rosas M, Lauder SN, Watson A, Dul M, Garcia-Diaz Y, Aldrovandi M, Heurich M, Hall J, Morrissey JH, Lacroix-Desmazes S, Delignat S, Jenkins PV, Collins PW, O'Donnell VBet al., 2018,

    Enzymatically oxidized phospholipids restore thrombin generation in coagulation factor deficiencies

    , JCI INSIGHT, Vol: 3, ISSN: 2379-3708
  • Journal article
    Hindley JW, Elani Y, McGilvery CM, Ali S, Bevan CL, Law R, Ces Oet al., 2018,

    Light-triggered enzymatic reactions in nested vesicle reactors

    , Nature Communications, Vol: 9, Pages: 1-6, ISSN: 2041-1723

    Cell-sized vesicles have tremendous potential both as miniaturised pL reaction vessels and in bottom-up synthetic biology as chassis for artificial cells. In both these areas the introduction of light-responsive modules affords increased functionality, for example, to initiate enzymatic reactions in the vesicle interior with spatiotemporal control. Here we report a system composed of nested vesicles where the inner compartments act as phototransducers, responding to ultraviolet irradiation through diacetylene polymerisation-induced pore formation to initiate enzymatic reactions. The controlled release and hydrolysis of a fluorogenic β-galactosidase substrate in the external compartment is demonstrated, where the rate of reaction can be modulated by varying ultraviolet exposure time. Such cell-like nested microreactor structures could be utilised in fields from biocatalysis through to drug delivery.
  • Journal article
    Elani Y, Trantidou T, Wylie D, Dekker L, Polizzi K, Law R, Ces Oet al., 2018,

    Constructing vesicle-based artificial cells with embedded living cells as organelle-like modules

    , Scientific Reports, Vol: 8, Pages: 1-8, ISSN: 2045-2322

    There is increasing interest in constructing artificial cells by functionalising lipid vesicles with biological and synthetic machinery. Due to their reduced complexity and lack of evolved biochemical pathways, the capabilities of artificial cells are limited in comparison to their biological counterparts. We show that encapsulating living cells in vesicles provides a means for artificial cells to leverage cellular biochemistry, with the encapsulated cells serving organelle-like functions as living modules inside a larger synthetic cell assembly. Using microfluidic technologies to construct such hybrid cellular bionic systems, we demonstrate that the vesicle host and the encapsulated cell operate in concert. The external architecture of the vesicle shields the cell from toxic surroundings, while the cell acts as a bioreactor module that processes encapsulated feedstock which is further processed by a synthetic enzymatic metabolism co-encapsulated in the vesicle.
  • Journal article
    Heide C, Ces O, Polizzi K, Kontoravdi Cet al., 2018,

    Creating cell-free protein synthesis factories

    , Pharmaceutical Bioprocessing, Vol: 6, Pages: 3-6, ISSN: 2048-9145
  • Journal article
    Tascini AS, Noro MG, Chen R, Seddon JM, Bresme Fet al., 2018,

    Understanding the interactions between sebum triglycerides and water: a molecular dynamics simulation study.

    , Physical Chemistry Chemical Physics, Vol: 20, Pages: 1848-1860, ISSN: 1463-9076

    In recent years, sebum oil has been found to play a key role in the regulation of the hydration of the outermost layer of the skin, the stratum corneum. Understanding how a major component of the sebum oil, the triglyceride tri-cis-6-hexadecenoin (TG), interacts with water is an important step in gaining insight into the water regulation function of the sebum oil. Here we use molecular dynamics simulations to investigate the structural and interfacial properties of TG in bulk and at the air and water interface. Our model performs very well in reproducing experimental results, such as density, surface tensions and surface pressure area isotherms. We show that triglyceride molecules in the liquid phase assemble together, through the glycerol group, forming a single percolating network. TG-air interfaces orient the lipids with the interface enriched with the hydrophobic tails and the glycerol groups buried inside. When in contact with water, the TG molecules at the interface orient the glycerol group towards the water phase and adopt a characteristic trident conformation. Water is shown to penetrate the TG layer thanks to the interaction with the oxygen atoms of the TG molecules, which acts as a pathway for water diffusion. The activation energy for the passage of water is found to be ≈9.5kBT at 310 K, showing that the layer is permeable to water diffusion.
  • Journal article
    Henry J, Chen X, Law RV, Hill RGet al., 2018,

    The investigation of the crystalline phases development in Macor glass ceramic

    , JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 38, Pages: 245-251, ISSN: 0955-2219
  • Journal article
    Salehi-Reyhani S, 2017,

    Evaluating single molecule detection methods for microarrays with high dynamic range for quantitative single cell analysis

    , Scientific Reports, Vol: 7, ISSN: 2045-2322

    Single molecule microarrays have been used in quantitative proteomics, in particular, single cell analysis requiring high sensitivity and ultra-low limits of detection. In this paper, several image analysis methods are evaluated for their ability to accurately enumerate single molecules bound to a microarray spot. Crucially, protein abundance in single cells can vary significantly and may span several orders of magnitude. This poses a challenge to single molecule image analysis. In order to quantitatively assess the performance of each method, synthetic image datasets are generated with known ground truth whereby the number of single molecules varies over 5 orders of magnitude with a range of signal to noise ratios. Experiments were performed on synthetic datasets whereby the number of single molecules per spot corresponds to realistic single cell distributions whose ground truth summary statistics are known. The methods of image analysis are assessed in their ability to accurately estimate the distribution parameters. It is shown that super-resolution image analysis methods can significantly improve counting accuracy and better cope with single molecule congestion. The results highlight the challenge posed by quantitative single cell analysis and the implications to performing such analyses using microarray based approaches are discussed.
  • Journal article
    Barlow NE, Bolognesi G, Haylock S, Flemming AJ, Brooks NJ, Barter LMC, Ces Oet al., 2017,

    Rheological Droplet Interface Bilayers (rheo-DIBs): Probing the Unstirred Water Layer Effect on Membrane Permeability via Spinning Disk Induced Shear Stress

    , Scientific Reports, Vol: 7, ISSN: 2045-2322

    A new rheological droplet interface bilayer (rheo-DIB) device is presented as a tool to apply shear stress on biological lipid membranes. Despite their exciting potential for affecting high-throughput membrane translocation studies, permeability assays conducted using DIBs have neglected the effect of the unstirred water layer (UWL). However as demonstrated in this study, neglecting this phenomenon can cause significant underestimates in membrane permeability measurements which in turn limits their ability to predict key processes such as drug translocation rates across lipid membranes. With the use of the rheo-DIB chip, the effective bilayer permeability can be modulated by applying shear stress to the droplet interfaces, inducing flow parallel to the DIB membranes. By analysing the relation between the effective membrane permeability and the applied stress, both the intrinsic membrane permeability and UWL thickness can be determined for the first time using this model membrane approach, thereby unlocking the potential of DIBs for undertaking diffusion assays. The results are also validated with numerical simulations.
  • Journal article
    Chen X, Chen X, Brauer DS, Wilson RM, Law RV, Hill RG, Karpukhina Net al., 2017,

    Sodium is not essential for high bioactivity of glasses

    , INTERNATIONAL JOURNAL OF APPLIED GLASS SCIENCE, Vol: 8, Pages: 428-437, ISSN: 2041-1286
  • Journal article
    Thomas JM, Friddin MS, Ces O, Elani Yet al., 2017,

    Programming membrane permeability using integrated membrane pores and blockers as molecular regulators

    , Chemical Communications, Vol: 53, Pages: 12282-12285, ISSN: 1359-7345

    We report a bottom-up synthetic biology approach to engineering vesicles with programmable permeabilities. Exploiting the concentration-dependent relationship between constitutively active pores (alpha-hemolysin) and blockers allows blockers to behave as molecular regulators for tuning permeability, enabling us to systematically modulate cargo release kinetics without changing the lipid fabric of the system.
  • Journal article
    de Bruin A, Friddin MS, Elani Y, Brooks N, Law R, Seddon J, Ces Oet al., 2017,

    A transparent 3D printed device for assembling droplet hydrogel bilayers (DHBs)

    , RSC Advances, Vol: 7, Pages: 47796-47800, ISSN: 2046-2069

    We report a new approach for assembling droplet hydrogel bilayers (DHBs) using a transparent 3D printed device. We characterise the transparency of our platform, confirm bilayer formation using electrical measurements and show that single-channel recordings can be obtained using our reusable rapid prototyped device. This method significantly reduces the cost and infrastructure required to develop devices for DHB assembly and downstream study.
  • Journal article
    Richens JL, Tyler AII, Barriga HMG, Bramble JP, Law RV, Brooks NJ, Seddon JM, Ces O, O'Shea Pet al., 2017,

    Spontaneous charged lipid transfer between lipid vesicles

    , Scientific Reports, Vol: 7, ISSN: 2045-2322

    An assay to study the spontaneous charged lipid transfer between lipid vesicles is described. A donor/acceptor vesicle system is employed, where neutrally charged acceptor vesicles are uorescentlylabelled with the electrostatic membrane probe Fluoresceinphosphatidylethanolamine (FPE).Upon addition of charged donor vesicles, transfer of negatively charged lipid occurs, resulting ina uorescently detectable change in the membrane potential of the acceptor vesicles. Using this approach we have studied the transfer properties of a range of lipids, varying both the headgroup and the chain length. At the low vesicle concentrations chosen, the transfer follows a rst-order process where lipid monomers are transferred presumably through the aqueous solution phase from donor to acceptor vesicle. The rate of transfer decreases with increasing chain length which is consistent with energy models previously reported for lipid monomer vesicle interactions. Our assay improves on existing methods allowing the study of a range of unmodi ed lipids, continuous monitoring of transfer and simpli ed experimental procedures.
  • Journal article
    Kluzek M, Tyler AII, Wang S, Chen R, Marques CM, Thalmann F, Seddon JM, Schmutz Met al., 2017,

    Influence of a pH-sensitive polymer on the structure of monoolein cubosomes

    , Soft Matter, Vol: 13, Pages: 7571-7577, ISSN: 1744-683X

    Cubosomes consist in submicron size particles of lipid bicontinuous cubic phases stabilized by surfactant polymers. They provide an appealing road towards the practical use of lipid cubic phases for pharmaceutical and cosmetic applications, and efforts are currently being made to control the encapsulation and release properties of these colloidal objects. We overcome in this work the lack of sensitivity of monoolein cubosomes to pH conditions by using a pH sensitive polymer designed to strongly interact with the lipid structure at low pH. Our cryo-transmission electron microscope (cryo-TEM) and small-angle X-ray scattering (SAXS) results show that in the presence of the polymer the cubic phase structure is preserved at neutral pH, albeit with a larger cell size. At pH 5.5, in the presence of the polymer, the nanostructure of the cubosome particles is significantly altered, providing a pathway to design pH-responsive cubosomes for applications in drug delivery.
  • Journal article
    Cornell CE, McCarthy NLC, Levental KR, Levental I, Brooks NJ, Keller SLet al., 2017,

    Lengths of n-alcohols govern how Lo-Ld mixing temperatures shift in synthetic and cell-derived membranes

    , Biophysical Journal, Vol: 113, Pages: 1-13, ISSN: 1542-0086

    A persistent challenge in membrane biophysics has been to quantitatively predict how membrane physical properties change upon addition of new amphiphiles (e.g., lipids, alcohols, peptides, or proteins) in order to assess whether the changes are large enough to plausibly result in biological ramifications. Because of their roles as general anesthetics, n-alcohols are perhaps the best-studied amphiphiles of this class. When n-alcohols are added to model and cell membranes, changes in membrane parameters tend to be modest. One striking exception is found in the large decrease in liquid-liquid miscibility transition temperatures (Tmix) observed when short-chain n-alcohols are incorporated into giant plasma membrane vesicles (GPMVs). Coexisting liquid-ordered and liquid-disordered phases are observed at temperatures below Tmix in GPMVs as well as in giant unilamellar vesicles (GUVs) composed of ternary mixtures of a lipid with a low melting temperature, a lipid with a high melting temperature, and cholesterol. Here, we find that when GUVs of canonical ternary mixtures are formed in aqueous solutions of short-chain n-alcohols (n ≤ 10), Tmix increases relative to GUVs in water. This shift is in the opposite direction from that reported for cell-derived GPMVs. The increase in Tmix is robust across GUVs of several types of lipids, ratios of lipids, types of short-chain n-alcohols, and concentrations of n-alcohols. However, as chain lengths of n-alcohols increase, nonmonotonic shifts in Tmix are observed. Alcohols with chain lengths of 10–14 carbons decrease Tmix in ternary GUVs of dioleoyl-PC/dipalmitoyl-PC/cholesterol, whereas 16 carbons increase Tmix again. Gray et al. observed a similar influence of the length of n-alcohols on the direction of the shift in Tmix. These results are consistent with a scenario in which the relative partitioning of n-alcohols between liquid-ordered and liquid-disordered phases evolves as the chain length of the n-alcohol increases.
  • Journal article
    Brooks NJ, Castiglione F, Doherty CM, Dolan A, Hill AJ, Hunt PA, Matthews RP, Mauri M, Mele A, Simonutti R, Villar-Garcia IJ, Weber CC, Welton Tet al., 2017,

    Linking the structures, free volumes, and properties of ionic liquid mixtures

    , Chemical Science, Vol: 8, Pages: 6359-6374, ISSN: 2041-6520

    The formation of ionic liquid (IL) mixtures has been proposed as an approach to rationally fine-tune the physicochemical properties of ILs for a variety of applications. However, the effects of forming such mixtures on the resultant properties of the liquids are only beginning to be understood. Towards a more complete understanding of both the thermodynamics of mixing ILs and the effect of mixing these liquids on their structures and physicochemical properties, the spatial arrangement and free volume of IL mixtures containing the common [C4C1im]+ cation and different anions have been systematically explored using small angle X-ray scattering (SAXS), positron annihilation lifetime spectroscopy (PALS) and 129Xe NMR techniques. Anion size has the greatest effect on the spatial arrangement of the ILs and their mixtures in terms of the size of the non-polar domains and inter-ion distances. It was found that differences in coulombic attraction between oppositely charged ions arising from the distribution of charge density amongst the atoms of the anion also significantly influences these inter-ion distances. PALS and 129Xe NMR results pertaining to the free volume of these mixtures were found to strongly correlate with each other despite the vastly different timescales of these techniques. Furthermore, the excess free volumes calculated from each of these measurements were in excellent agreement with the excess volumes of mixing measured for the IL mixtures investigated. The correspondence of these techniques indicates that the static and dynamic free volume of these liquid mixtures are strongly linked. Consequently, fluxional processes such as hydrogen bonding do not significantly contribute to the free volumes of these liquids compared to the spatial arrangement of ions arising from their size, shape and coulombic attraction. Given the relationship between free volume and transport properties such as viscosity and conductivity, these results provide a link between the s
  • Conference paper
    Tascini AS, Chen R, Seddon JM, Bresme Fet al., 2017,

    How wettable is the skin surface?

    , 19th IUPAB Congress / 11th EBSA Congress, Publisher: SPRINGER, Pages: S232-S232, ISSN: 0175-7571
  • Conference paper
    Gainar A, Tyler AII, Brooks NJ, Seddon JMet al., 2017,

    Understanding the lyotropic phase behaviour of cytochrome-c incorporated in monoolein mesophases

    , 19th IUPAB Congress / 11th EBSA Congress, Publisher: SPRINGER, Pages: S120-S120, ISSN: 0175-7571
  • Conference paper
    Barriga HM, Ces O, Law RV, Brooks NJ, Seddon JM, Stevens MMet al., 2017,

    Model membrane systems for protein therapeutics

    , 19th IUPAB Congress / 11th EBSA Congress, Publisher: SPRINGER, Pages: S117-S117, ISSN: 0175-7571

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