145 results found
Rowlands LJ, Marks A, Sanderson JM, et al., 2020, O-17 NMR spectroscopy as a tool to study hydrogen bonding of cholesterol in lipid bilayers, CHEMICAL COMMUNICATIONS, Vol: 56, Pages: 14499-14502, ISSN: 1359-7345
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.
Barriga H, Ces O, Law R, et al., 2019, Engineering swollen cubosomes using cholesterol and anionic lipids, Langmuir: the ACS journal of surfaces and colloids, Vol: 35, Pages: 16521-16527, ISSN: 0743-7463
Dispersions of non-lamellar lipid membrane assemblies are gaining increasing interest for drug delivery and protein therapeutic application. A key bottleneck has been the lack of rational design rules for these systems linking different lipid species and conditions to defined lattice parameters and structures. We have developed robust methods to form cubosomes (nanoparticles with a porous internal structure) with water channel diameters of up to 171 Å which are over 4 times larger than archetypal cubosome structures. The water channel diameter can be tuned via the incorporation of cholesterol and the charged lipids DOPA, DOPG or DOPS. We have found that large molecules can be incorporated into the porous cubosome structure and these molecules can interact with the internal cubosome membrane. This offers huge potential for accessible encapsulation and protection of biomolecules, and development of confined interfacial reaction environments.
Hindley JW, Zheleva DG, Elani Y, et al., 2019, Building a synthetic mechanosensitive signaling pathway in compartmentalized artificial cells, Proceedings of the National Academy of Sciences, Vol: 116, Pages: 16711-16716, ISSN: 0027-8424
To date reconstitution of one of the fundamental methods of cell communication, the signaling pathway, has been unaddressed in the bottom-up construction of artificial cells (ACs). Such developments are needed to increase the functionality and biomimicry of ACs, accelerating their translation and application in biotechnology. Here we report the construction of a de novo synthetic signaling pathway in microscale nested vesicles. Vesicle cell models respond to external calcium signals through activation of an intracellular interaction between phospholipase A2 and a mechanosensitive channel present in the internal membranes, triggering content mixing between compartments and controlling cell fluorescence. Emulsion-based approaches to AC construction are therefore shown to be ideal for the quick design and testing of new signaling networks and can readily include synthetic molecules difficult to introduce to biological cells. This work represents a foundation for the engineering of multi-compartment-spanning designer pathways that can be utilised to control downstream events inside an artificial cell, leading to the assembly of micromachines capable of sensing and responding to changes in their local environment.
Rowlands L, Wrobel C, Law RV, 2019, NMR Studies of Phospholipid Motion using Lanthanide Induced Shifts, Joint 12th EBSA European Biophysics Congress / 10th IUPAP International Conference on Biological Physics (ICBP), Publisher: SPRINGER, Pages: S113-S113, ISSN: 0175-7571
Khan H, Seddon JM, Law RV, et al., 2019, Effect of glycerol with sodium chloride on the Krafft point of sodium dodecyl sulfate using surface tension, Journal of Colloid and Interface Science, Vol: 538, Pages: 75-82, ISSN: 0021-9797
The effect of glycerol with sodium chloride (NaCl) on the phase behaviour of sodium dodecyl sulfate (SDS) near the Krafft point was studied by surface tension analysis using the pendant drop method. The critical micelle concentration (CMC) and Krafft Temperature (TK) of SDS in water: glycerol mixtures, across the full composition range, and in NaCl solutions within 0.005–0.1 M were obtained. The pendant drop method successfully allowed us to determine the Krafft point of SDS in high glycerol systems where other traditional methods (e.g. conductivity) have been ineffective. Overall the addition of glycerol increases the CMC and the TK, thus shifting the Krafft point of SDS to higher temperatures (increasing crystallisation temperatures) and higher SDS content in the presence of glycerol, which is interpreted as a result of the reduction in solvent polarity which opposes micellization. The addition of NaCl to the SDS – water-glycerol systems brings the CMC back down, while having no significant effect on the TK. Our results establish a robust route for tuning the Krafft point of model surfactant SDS by adjusting solvent quality and salt content.
Jia J, White ER, Clancy AJ, et 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.
Karamdad K, Hindley J, Friddin MS, et 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.
Hindley JW, Elani Y, McGilvery CM, et 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.
Elani Y, Trantidou T, Wylie D, et 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.
Henry J, Chen X, Law RV, et 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
Chen X, Chen X, Brauer DS, et 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
de Bruin A, Friddin MS, Elani Y, et 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.
Richens JL, Tyler AII, Barriga HMG, et 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.
Barriga HM, Ces O, Law RV, et al., 2017, Model membrane systems for protein therapeutics, 19th IUPAB Congress / 11th EBSA Congress, Publisher: SPRINGER, Pages: S117-S117, ISSN: 0175-7571
Trantidou T, Friddin M, Elani Y, et al., 2017, Engineering compartmentalized biomimetic micro- and nanocontainers, ACS Nano, Vol: 11, Pages: 6549-6565, ISSN: 1936-086X
Compartmentalization of biological content and function is a key architectural feature in biology, where membrane bound micro- and nanocompartments are used for performing a host of highly specialized and tightly regulated biological functions. The benefit of compartmentalization as a design principle is behind its ubiquity in cells and has led to it being a central engineering theme in construction of artificial cell-like systems. In this review, we discuss the attractions of designing compartmentalized membrane-bound constructs and review a range of biomimetic membrane architectures that span length scales, focusing on lipid-based structures but also addressing polymer-based and hybrid approaches. These include nested vesicles, multicompartment vesicles, large-scale vesicle networks, as well as droplet interface bilayers, and double-emulsion multiphase systems (multisomes). We outline key examples of how such structures have been functionalized with biological and synthetic machinery, for example, to manufacture and deliver drugs and metabolic compounds, to replicate intracellular signaling cascades, and to demonstrate collective behaviors as minimal tissue constructs. Particular emphasis is placed on the applications of these architectures and the state-of-the-art microfluidic engineering required to fabricate, functionalize, and precisely assemble them. Finally, we outline the future directions of these technologies and highlight how they could be applied to engineer the next generation of cell models, therapeutic agents, and microreactors, together with the diverse applications in the emerging field of bottom-up synthetic biology.
Gonzalez MA, Barriga HMG, Richens JL, et al., 2017, How does ytterbium chloride interact with DMPC bilayers? A computational and experimental study, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 19, Pages: 9199-9209, ISSN: 1463-9076
Lanthanide salts have been studied for many years, primarily in Nuclear Magnetic Resonance (NMR) experiments of mixed lipid–protein systems and more recently to study lipid flip-flop in model membrane systems. It is well recognised that lanthanide salts can influence the behaviour of both lipid and protein systems, however a full molecular level description of lipid–lanthanide interactions is still outstanding. Here we present a study of lanthanide–bilayer interactions, using molecular dynamics computer simulations, fluorescence electrostatic potential experiments and nuclear magnetic resonance. Computer simulations reveal the microscopic structure of DMPC lipid bilayers in the presence of Yb3+, and a surprising ability of the membranes to adsorb significant concentrations of Yb3+ without disrupting the overall membrane structure. At concentrations commonly used in NMR experiments, Yb3+ ions bind strongly to 5 lipids, inducing a small decrease of the area per lipid and a slight increase of the ordering of the aliphatic chains and the bilayer thickness. The area compressibility modulus increases by a factor of two, with respect to the free-salt case, showing that Yb3+ ions make the bilayer more rigid. These modifications of the bilayer properties should be taken into account in the interpretation of NMR experiments.
Gao Y, Karpukhina N, Law RV, 2016, Phase segregation in hydroxyfluorapatite solid solution at high temperatures studied by combined XRD/solid state NMR, RSC Advances, Vol: 6, Pages: 103782-103790, ISSN: 2046-2069
Fluoride substituted apatite is a key player among currently existing biomaterials. The 19F MAS-NMR is perhaps the most and only reliable technique to detect fluoride substitution in apatite. Typically any 19F MAS-NMR signal between −101.0 and −107.0 ppm is often used to identify fluoride substitution in apatite. Until now no explanation has been given as to why there is such a large variation in the NMR signals of these crystalline species. In this study, for the first time, we were able to explain this large variation in the 19F chemical shift values often seen in the literature. Hydroxyfluorapatites (FHA) with varied fluoride substitution and free from other substitutions have been synthesized via solution route followed by heat treatment in air at different temperatures up to 900 °C. Solid-state nuclear magnetic resonance (19F and 31P MAS-NMR) and X-ray diffraction (XRD) were used to characterize the synthesized powder samples. Formation of solid solution with varied hydroxyl/fluoride ratio was observed after the heat treatment up to a temperature of 300 °C. FHA samples decomposed to β-tricalcium phosphate (β-TCP) at higher temperature, which started from 20% F sample at 750 °C. With increasing F%, the FHA became more thermally stable and 80% F sample did not show β-TCP until 900 °C. An empirical nonlinear correlation between 19F NMR chemical shift and relative F% had been established. The mechanism of FHA solid solution formation and its thermal instability is proposed.
Chan CL, Bolognesi G, Bhandarkar A, et al., 2016, DROPLAY: laser writing of functional patterns within biological microdroplet displays, Lab on a Chip, Vol: 16, Pages: 4621-4627, ISSN: 1473-0197
In this study, we introduce an optofluidic method for the rapid construction of large-area cell-sized droplet assemblieswith user-defined re-writable two-dimensional patterns of functional droplets. Light responsive water-in-oil dropletscapable of releasing fluorescent dye molecules upon exposure were generated and self-assembled into arrays in amicrofluidic device. This biological architecture was exploited by the scanning laser of a confocal microscope to ‘write’ userdefined patterns of differentiated (fluorescent) droplets in a network of originally undifferentiated (non-fluorescent)droplets. As a result, long lasting images were produced on a droplet fabric with droplets acting as pixels of a biologicalmonitor, which can be erased and re-written on-demand. Regio-specific light-induced droplet differentiation within a largepopulation of droplets provides a new paradigm for the rapid construction of bio-synthetic systems with potential as tissuemimics and biological display materials.
Friddin MS, Bolognesi G, Elani Y, et al., 2016, Optically assembled droplet interface bilayer (OptiDIB) networks from cell-sized microdroplets, Soft Matter, Vol: 12, Pages: 7731-7734, ISSN: 1744-6848
We report a new platform technology to systematically assemble droplet interface bilayer (DIB) networks in user-defined 3D architectures from cell-sized droplets using optical tweezers. Our OptiDIB platform is the first demonstration of optical trapping to precisely construct 3D DIB networks, paving the way for the development of a new generation of modular bio-systems.
Kusumoto H, Alolghaserni S, Woodfine B, et al., 2016, The effect of phosphate, fluorine, and soda content of the glass on the mechanical properties of the glass ionomer (polyalkenoate) cements, JOURNAL OF NON-CRYSTALLINE SOLIDS, Vol: 449, Pages: 94-99, ISSN: 0022-3093
Friddin MS, Bolognesi G, Elani Y, et al., 2016, The optical assembly of bilayer networks from cell-sized droplets for synthetic biology, Systems and Synthetic Biology
Friddin MS, Bolognesi G, Elani Y, et al., 2016, Optical tweezers to assemble 2D and 3D droplet interface bilayer networks from cell-sized droplets, EMBL Microfluidics
Elani Y, Solvas XC, Edel JB, et al., 2016, Microfluidic generation of encapsulated droplet interface bilayer networks (multisomes) and their use as cell-like reactors., Chemical Communications, Vol: 52, Pages: 5961-5964, ISSN: 1364-548X
Compartmentalised structures based on droplet interface bilayers (DIBs), including multisomes and compartmentalised vesicles, are seen by many as the next generation of biomimetic soft matter devices. Herein, we outline a microfluidic approach for the construction of miniaturised multisomes of pL volumes in high-throughput and demonstrate their potential as vehicles for in situ chemical synthesis.
Karamdad K, Law R, Seddon J, et al., 2016, Studying the effects of asymmetry on the bending rigidity of lipid membranes formed by microfluidics, Chemical Communications (London), Vol: 52, Pages: 5277-5280, ISSN: 0009-241X
In this article we detail a robust high-throughput microfluidic platform capable of fabricating either symmetric or asymmetric giant unilamellar vesicles (GUVs) and characterise the mechanical properties of their membranes.
Rashid S, Law RV, Isakovic AF, et al., 2016, Modulation of Gel Phase Model Membranes by Vitamin D-Related Proteins, 60th Annual Meeting of the Biophysical-Society, Publisher: CELL PRESS, Pages: 420A-420A, ISSN: 0006-3495
Ces O, Elani Y, Karamdad K, et al., 2016, Novel microfluidic technologies for the bottom-up construction of artificial cells
This talk will outline novel microfluidic strategies for biomembrane engineering that are capable of fabricating vesicles , droplet interface bilayer networks , multisomes  and artificial tissues  where parameters such as membrane asymmetry, membrane curvature, compartment connectivity and individual compartment contents can be controlled. Various bulk methods, such as extrusion, gentle hydration and electroformation, have been synonymous with the formation of lipid vesicles over recent years. However these strategies suffer from significant shortcomings associated with these processes including limited control of vesicle structural parameters such as size, lamellarity, membrane composition and internal contents. To address this technological bottleneck we have developed novel microfluidic platforms to form lipid vesicles in high-Throughput with full control over the composition of both the inner and outer leaflet of the membrane thereby enabling the manufacture of symmetric and asymmetric vesicles. This is achieved by manufacturing microfluidic channels with a step junction, produced by double-layer photolithography, which facilitates the transfer of a W/O emulsion across an oil-water phase boundary and the self-Assembly of a phospholipid bilayer. These platforms are being used to explore the role of asymmetry in biological systems  and study the engineering rules that regulate membrane mediated protein-protein interactions . In addition, these technologies are enabling the construction of biological machines capable of acting as micro-reactors , environmental sensors and smart delivery vehicles  as well as complex multi-compartment artificial cells where the contents and connectivity of each compartment can be controlled. These compartments are separated by biological functional membranes that can facilitate transport between the compartments themselves and between the compartments and external environment. This approach has led to the deve
Friddin MS, Bolognesi G, Elani Y, et al., 2016, Light-driven drag and drop assembly of micron-scale bilayer networks for synthetic biology, Pages: 545-546
We have developed a new method to assemble single- or multi-layered networks of droplet interface bilayers (DIBs) from cell-sized droplets using a single beam optical trap (optical tweezers). The novelty of our approach is the ability to directly trap the microdroplets with the laser and manipulate them in 3D to construct DIB networks of user-defined architectures. Our method does not require a complex optical setup, is versatile, contactless, benefits from both high spatial and temporal resolution, and could set a new paradigm for the assembly of smart, synthetic biosystems.
Carreras P, Elani Y, Law RV, et al., 2015, A microfluidic platform for size-dependent generation of droplet interface bilayer networks on rails, Biomicrofluidics, Vol: 9, ISSN: 1932-1058
Dropletinterface bilayer (DIB) networks are emerging as a cornerstone technology for the bottom up construction of cell-like and tissue-like structures and bio-devices. They are an exciting and versatile model-membrane platform, seeing increasing use in the disciplines of synthetic biology, chemical biology, and membrane biophysics. DIBs are formed when lipid-coated water-in-oil droplets are brought together—oil is excluded from the interface, resulting in a bilayer. Perhaps the greatest feature of the DIB platform is the ability to generate bilayer networks by connecting multiple droplets together, which can in turn be used in applications ranging from tissue mimics, multicellular models, and bio-devices. For such applications, the construction and release of DIB networks of defined size and composition on-demand is crucial. We have developed a droplet-based microfluidic method for the generation of different sized DIB networks (300–1500 pl droplets) on-chip. We do this by employing a droplet-on-rails strategy where droplets are guided down designated paths of a chip with the aid of microfabricated grooves or “rails,” and droplets of set sizes are selectively directed to specific rails using auxiliary flows. In this way we can uniquely produce parallel bilayer networks of defined sizes. By trapping several droplets in a rail, extended DIB networks containing up to 20 sequential bilayers could be constructed. The trapped DIB arrays can be composed of different lipid types and can be released on-demand and regenerated within seconds. We show that chemical signals can be propagated across the bio-network by transplanting enzymatic reaction cascades for inter-droplet communication.
Arregui CDLC, Purdie JA, Haslam CA, et al., 2015, Optimised conditions for the synthesis of 17O and 18O labelled cholesterol, Chemistry and Physics of Lipids, Vol: 195, Pages: 58-62, ISSN: 1873-2941
Conditions are described for the preparation of cholesterol with 17O and 18O labels from i-cholesteryl methyl ether using minimal amounts of isotopically enriched water. Optimum yields employed trifluoromethanesulfonic acid as catalyst in 1,4-dioxane at room temperature with 5 equivalents of water. An isotopic enrichment >90% of that of the water used for the reaction could be attained. Tetrafluoroboric acid could also be used as catalyst, at the expense of a lower overall reaction yield. Byproducts from the reaction included dicholesteryl ether, methyl cholesteryl ether, compounds formed by ether hydrolysis, and olefins arising from elimination reactions. Reactions in tetrahydrofuran yielded significant amounts of cholesteryl ethers formed by reaction with alcohols arising from hydrolysis of the solvent.
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