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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., Electrophysiology shows asymmetric lysophosphatidylcholine-containing DIBs trigger mechanosensitive channel gating, enabling user-designed, autonomous flux pathways in droplet networks.

Simple diffusion of molecular entities through a phospholipid bilayer, is a phenomenon of great importance to the pharmaceutical and agricultural industries. Current model lipid systems to probe this typically only employ fluorescence as a readout, thus limiting the range of assessable chemical matter that can be studied. We report a new technology platform, the UV-DIB, which facilitates label free measurement of small molecule translocation rates. This is based upon the coupling of droplet interface bilayer technology with implemented fiber optics to facilitate analysis via ultraviolet spectroscopy, in custom designed PMMA wells. To improve on current DIB technology, the platform was designed to be reusable, with a high sampling rate and a limit of UV detection in the low μM regime. We demonstrate the use of our system to quantify passive diffusion in a reproducible and rapid manner where the system was validated by investigating multiple permeants of varying physicochemical properties across a range of lipid interfaces, each demonstrating differing kinetics. Our system permits the interrogation of structural dependence on the permeation rate of a given compound. We present this ability from two structural perspectives, that of the membrane, and the permeant. We observed a reduction in permeability between pure DOPC and DPhPC interfaces, concurring with literature and demonstrating our ability to study the effects of lipid composition on permeability. In relation to the effects of permeant structure, our device facilitated the rank ordering of various compounds from the xanthine class of compounds, where the structure of each permeant differed by a single group alteration. We found that DIBs were stable up to 5% DMSO, a molecule often used to aid solubilisation of pharmaceutical and agrochemical compounds. The ability of our device to rank-order compounds with such minor structural differences provides a level of precision that is rarely seen in current, industrially applied technologies.

The interactions between small molecules and keratins are poorly understood. In this paper, a nuclear magnetic resonance method is presented to measure changes in the 1 H T 1 relaxation times of small molecules in human hair keratin to quantify their interaction with the fibre. Two populations of small-molecule compounds were identified with distinct relaxation times, demonstrating the partitioning of the compounds into different keratin environments. The changes in relaxation time for solvent in hair compared with bulk solvent were shown to be related to the molecular weight (MW) and the partition coefficient, LogP, of the solvent investigated. Compounds with low MWs and high hydrophilicities had greater reductions in their T 1 relaxation times and therefore experienced increased interactions with the hair fibre. The relative population sizes were also calculated. This is a significant step towards modelling the behaviour of small molecules in keratinous materials and other large insoluble fibrous proteins.

Dispersions of nonlamellar 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 porous internal structures) 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 lipid DOPA, DOPG, or DOPS. We have found that large molecules can be incorporated into the porous cubosome structure and that 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.

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.

The role of cholesterol (Chol) in promoting lamellar phase formation in mixtures with 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (Lyso-PPC) in excess water was investigated using multinuclear solid-state NMR and X-ray scattering. It was found that mixtures containing Chol and Lyso-PPC form a liquid-ordered (Lo) lamellar phase over a range of temperatures and concentrations, as previously observed in mixtures of Chol with various diacylphospholipids. The maximum quadrupolar splitting of the 2H-NMR powder patterns for samples containing per-deuterated Lyso-PPC were 40-50 kHz which is strongly indicative of an Lo phase. This evidence was supported by wide angle X-ray scattering data which showed a characteristic diffuse peak centred at 4.2 Å. The Lo phase coexists with an isotropic Lyso-PPC phase at Chol concentrations up to 70 mol% Chol, and with Chol crystals at Chol concentrations above this value. Below 70 mol% Chol, an increase in the concentration of Chol in the system caused a corresponding increase in the proportion of the Lo phase present compared with the amount of isotropic Lyso-PPC. The chemical-shift anisotropy (CSA) of the static 31P-NMR spectra of the Lo phase showed the symmetry of a lamellar phase, but the linewidth, Δσ, was much narrower than CSA powder patterns obtained for diacylphospholipids in similar conditions, being ∼20 ppm as opposed to ∼40 ppm, respectively.

The commercially available, machinable, fluormica glass-ceramic, Macor ® , was remelted to produce a glass. This glass was then characterized by differential scanning calorimetry (DSC), combined differential thermal analysis/thermal gravimetric analysis (DTA/TGA), X-ray powder diffraction (XRD) and 19 F magic angle spinning −nuclear magnetic resonance (MAS-NMR). The Macor ® glass was shown to crystallize to chondrodite (Mg 5 F 2 (SiO 4 ) 2 ), followed by the conversion of chondrodite to norbergite (Mg 3 SiO 4 F 2 ) and the conversion of norbegite to a potassium fluorphlogopite phase (KMg 3 AlSi 3 O 10 F 2 ). The glass exhibited an optimum nucleation temperature just above its glass transition temperature, which is indicative of a nucleation route involving amorphous phase separation. The 19 F MAS-NMR spectra showed the fluorine environments being present as F-Mg(3) in the original glass, the chondrodite, norbergite and fluorphlogopite phases, indicating that the fluorine structure is conserved throughout the crystallization process. The activation energies for crystallization were found to be 215, 431 and 251 kJ mol −1 for chondrodite, norbergite and fluorphlogopite, respectively.

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.

Two series of glasses were produced by systematically substituting magnesium for calcium and strontium in the glass compositions, 4.5SiO2. 3Al2O3. 1.5P2O5. (3-x)CaO/SrO. xMgO. (2-y)CaF2/SrF2. yMgF2, 0 ≥ x ≥ 3, 0 ≥ y ≥ 2 and these glasses were characterised by 19F, 31P, 27Al, and 29Si MAS-NMR spectroscopy. The substitution of magnesium for calcium and strontium resulted in the gradual formation of F-Mg(n) species over the F-Ca(n) and F-Sr(n) with additional loss of AlF species. The 31P and 27Al MAS-NMR spectra showed the presence of Al-O-PO33− species charge balanced by a mixture of Ca2+ and Mg2+ or Sr2+ and Mg2+. In addition to that, the 31P MAS-NMR spectrum of the fully magnesium substituted glass showed the presence of amorphous magnesium pyrophosphate, Mg2P2O7. Al(IV) was the major Al species with small amount of Al(V) and Al(VI), but the amount of Al(V) increased with increase in magnesium substitution. Moreover, the fully magnesium substituted fluoro-phospho-aluminosilicate glass resulted in the more polymerised silicate network with increased number of the bridging oxygen on SiO4 tetrahedra. Keywords: MAS-NMR, Aluminosilicate glass, Magnesium, Calcium, Strontium

The authors would like to thank the Department of Trade and Industry, UK, under the project number of TP/5/REG/6/I/H0669A.

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.

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.

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.

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.

We detail an approach for constructing asymmetric membranes and characterising their mechanical properties, leading to the first measurement of the effect of asymmetry on lipid bilayer mechanics. Our results demonstrate that asymmetry induces a significant increase in rigidity compared to symmetric membranes. Given that all biological membranes are asymmetric our findings have profound implications for the role of this phenomenon in biology.

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

This study aims to demonstrate that excellent bioactivity of glass can be achieved without the presence of an alkali metal component in glass composition. In vitro bioactivity of two sodium-free glasses based on the quaternary system SiO2-P2O5-CaO-CaF2 with 0 and 4.5 mol% CaF2 content was investigated and compared with the sodium containing glasses with equivalent amount of CaF2. The formation of apatite after immersion in Tris buffer was followed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), 31P and 19F solid state MAS-NMR. The dissolution study was completed by ion release measurements in Tris buffer. The results show that sodium free bioactive glasses formed apatite at 3 hours of immersion in Tris buffer, which is as fast as the corresponding sodium containing composition. This signifies that sodium is not an essential component in bioactive glasses and it is possible to make equally degradable bioactive glasses with or without sodium. The results presented here also emphasize the central role of the glass compositions design which is based on understanding of structural role of components and/or predicting the network connectivity of glasses.

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 fluorescently labelled with the electrostatic membrane probe Fluoresceinphosphatidylethanolamine (FPE). Upon addition of charged donor vesicles, transfer of negatively charged lipid occurs, resulting in a fluorescently 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 first-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 unmodified lipids, continuous monitoring of transfer and simplified experimental procedures.

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.

Lanthanide salts have been studied for many years, primarily in 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 simu-lations, fluorescence electrostatic potential experiments and Nuclear Magnetic Resonance. Com-puter simulations reveal the microscopic structure of DMPC lipid bilayers in the presence of Yb 3+ , and a surprising ability of the membranes to adsorb significant concentrations of Yb 3+ without significant disruption of the overall membrane structure. The Yb 3+ ions bind strongly to the lipids via the oxygen atoms in the lipid head group. We find that the cations are coordinated to 4-5 lipids for a wide range of Lanthanide:lipid ratios and temperatures. Addition of Yb 3+ results in a small decrease of the area per lipid with a concomitant increase of the ordering of the aliphatic chains and the bilayer thickness. The addition of Yb 3+ at standard concentrations commonly used in the NMR, induces an increase of the membrane electrostatic potential, ∼ 110 mV and a large change in the head-group orientation, which aligns in the direction normal to the bilayer plane. In addition the area compressibility modulus (stiffness) of DMPC having Ytterbium salt is 2.6 time higher than the membrane free-salt. These changes in the membrane properties are enhanced with salt con-centration, and should be taken into account in the interpretation of NMR experiments performed with Lanthanides.

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.

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.

Siloxane/poly(L-lactic acid)/vaterite hybrid (SiPVH) fibremats constantly release calcium ions and ionic silicon species that have the potential to promote bone regeneration. In order to improve the mechanical properties of the SiPVH fibremats, the effect of various silixane-containing vaterite (denoted by SiV) content (10-60 wt%) on tensile properties was assessed. SiPVH fibremats with 30 wt% SiV content showed the highest tensile strength of 2.87 ± 0.39 MPa. Based on the energy-dissipation mechanism, failure initiated at the stress concentration points such as pores on the fibre surfaces or filler particles. In the case of the SiPVH fibremats with 20 and 30 wt% SiV, stress concentration occurred around the filler particles, where the applied energy was directly converted to small volume dilatation around the filler particles during failure of the fibres. This mechanism can be applied only when the material contains the polymer and the filler particles in specific ratios; 20 and 30 wt% filler content in the fibremat in this work. To coat the fibre surfaces with bone-like apatite SiPVH fibremats were soaked in modified simulated body fluid (1.5 SBF). Bone-like apatite formed on the surfaces of SiPVH fibremats with more than 30 wt% of SiV content in 1 day of soaking. These results reveal that the SiPVH fibremats containing 30 wt% SiV have suitable mechanical properties for bone filler materials.

Sphingomyelin is the only sphingolipid occurring naturally in mammalian cells and can form up to 50% of the total phospholipid content of the myelin sheath which surrounds nerves. Having predominantly long, saturated acyl chains, it has a relatively high chain melting temperature and has been strongly associated with formation of lipid microdomains. Here, the lyotropic phase behaviour of sphingomyelin from three different natural sources (bovine brain, egg yolk and milk) in excess water is studied as a function of temperature and pressure by small- and wide-angle X-ray scattering, and solid state NMR. The different hydrocarbon chain length distributions of the three lipid extracts results in significant differences in their gel phase structure; both the bovine brain and egg yolk sphingomyelins can form a ripple gel phase but milk sphingomyelin forms an interdigitated gel phase due to the high degree of chain mismatch in its longer hydrocarbon chain components.

Objective. This study reports real time neutron diffraction on the Empress II glass-ceramic system. Methods . The commercial glass-ceramics was characterized by real time neutron diffraction, 31 P and 29 Si solid-state MAS-NMR, DSC and XRD. Results. On heating, the as-received glass ceramic contained lithium disilicate (Li 2 Si 2 O 5 ), which melted with increasing temperature. This was revealed by neutron diffraction which showed the Bragg peaks for this phase had disappeared by 958 °C in agreement with thermal analysis. On cooling lithium metasilicate (Li 2 SiO 3 ) started to form at around 916 °C and a minor phase of cristobalite at around 852 °C. The unit cell volume of both Li-silicate phases increased linearly with temperature at a rate of +17 × 10 −3 A 3 .°C −1 . Room temperature powder X-ray diffraction (XRD) of the material after cooling confirms presence of the lithium metasilicate and cristobalite as the main phases and shows, in addition, small amount of lithium disilicate and orthophosphate. 31 P MAS-NMR reveals presence of the lithiorthophosphate (Li 3 PO 4 ) before and after heat treatment. The melting of lithium disilicate on heating and crystallisation of lithium metasilicate on cooling agree with endothermic and exotermic features respectively observed by DSC. 29 Si MAS-NMR shows presence of lithium disilicate phase in the as-received glass-ceramic, though not in the major proportion, and lithium metasilicate in the material after heat treatment. Both phases have significantly long T 1 relaxation time, especially the lithium metasilicate, therefore, a quantitative analysis of the 29 Si MAS-NMR spectra was not attempted. Significance. The findings of the present work demonstrate importance of the commercially designed processing parameters in order to preserve desired characteristics of the material. Processing the Empress II at a rate slower than recommended 60 °C min −1 or long isothermal hold at the maximal processing temperature 920 °C can cause crystallization of lithium metasilicate and cristobalite instead of lithium disilicate as major phase.

Over a range of hydration, unsaturated diacylglycerol/phosphatidylcholine mixtures adopt an inverse micellar cubic phase, of crystallographic space group Fd3m. In this study hydrated DOPC:DOG mixtures with a molar ratio close to 1 : 2 were examined as a function of hydrostatic pressure, using synchrotron X-ray diffraction. The small-angle diffraction pattern at atmospheric pressure was used to calculate 2-D sections through the electron density map. Pressure initially has very little effect on the structure of the Fd3m cubic phase, in contrast to its effect on hydrated inverse bicontinuous cubic phases. At close to 2 kbar, a sharp transition occurs from the Fd3m phase to a pair of coexisting phases, an inverse hexagonal H(II) phase plus an (ordered) lamellar phase. Upon increasing the pressure to 3 kbar, a further sharp transition occurs from the H(II) phase to a (fluid) lamellar phase, in coexistence with the ordered lamellar phase. These transitions are fully reversible, but show hysteresis. Remarkably, the lattice parameter of the Fd3m phase is practically independent of pressure. These results show that these two lipids are miscible at low pressure, adopting a single lyotropic phase (Fd3m); they then become immiscible above a critical pressure, phase separating into DOPC-rich and DOG-rich phases.

Crystallisation of a fluorapatite (FAp) (Ca 5 (PO 4 ) 3 F) glass-ceramic has been studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), small angle neutron scattering (SANS), time-of-flight (TOF) neutron diffraction and multinuclear 19 F, 31 P, 27 Al, 29 Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. During crystallisation of FAp, fluorine is used in forming the FAp phase, since fluorine is known to reduce the glass transition temperature ( T g ), the T g of the residual glass increases on FAp crystallisation, which will restrict the growth of the FAp crystals. The XRD patterns of the heat-treated glass show the presence of FAp in addition there is marked line broadening. Debye–Scherrer analysis of the line broadening gives an average crystallite size of approximately 11–21 nm. SANS shows the glass to be single phase with no evidence of amorphous phase separation. SANS analysis of the heat-treated glass shows a single peak at q = 0.036 A − 1 corresponding to FAp crystallites of about 28 nm. 19 F MAS NMR shows a broad resonance identified as F-Ca(n) species in the glass, which narrows down on heat treatment and moves to position close to the F-Ca(3) site in calcium FAp. 31 P MAS NMR of the glass showed orthophosphate in structure ( Q 0 ) with a small amount of pyrophosphate (P-O-P and/or Al-O-P). On heat treatment the resonance narrows and shifts to 2 ppm corresponding to crystalline FAp. MAS NMR data suggests presence of small amount of Mg substituted into the lattice. It is thought that the observation of nano-crystals is aided by the low fluorine content of this glass. We have proposed semi-empirical rules for designing nano-crystalline oxyfluoride phases in glass-ceramic materials.

The influence of substituting strontium for calcium in the following glass series 49.46 SiO 2 –1.07 P 2 O 5 –(23.08-X) CaO–X SrO–26.38 Na 2 O was studied on the physical properties. Solid state nuclear magnetic resonance and vibrational spectroscopy showed that the glasses were predominantly composed of Q 2 silicate chains. Addition of strontium did not result in any structural alteration of the glass network due to the similar role of SrO compared with that of CaO. The density increased with strontium content whilst the oxygen density decreased indicating a more expanded glass network. The glass transition temperature reduced with strontium substitution in a linear fashion and there was no evidence of a mixed alkaline earth effect with a lower than expected glass transition temperature. Dilatometric softening points also reduced with increasing strontium content, whilst the thermal expansion coefficients increased. The results are consistent with a weaker network as a result of the lower charge to size ratio of Sr 2+ compared to Ca 2+ .

We report the real time crystallisation of an apatite–mullite glass ceramic, 4.5SiO2–3.0Al2O3–1.5P2O5–3.0CaO–1.5CaF2, analysed by time-of-flight (TOF) neutron diffraction and Rietveld refinement. The glass ceramic of this particular composition exhibits superior mechanical strength as was demonstrated earlier. The as-cast glass was heated up to 1200 °C with a 30 min isothermal hold, followed by cooling with the ramp stages at 2 °C min−1. On heating, fluorapatite (FAP—Ca5(PO4)3 F ) crystallised at around 850 °C and stabilised at around 908 °C. Mullite (Al6Si2O13) began to crystallise just above 1000 °C, which reinitiated the FAP crystallisation, with the FAP to mullite molar ratio decreasing linearly to around 1020 °C when the ratio stabilised to approximately 1:1. Dissolution of these two phases started at around 1130 °C but did not complete by 1200 °C. On cooling, cristabolite and quartz (berlinite) polymorphs of the aluminium phosphate, AlPO4, crystallised at around 1025 °C. The neutron diffraction results are consistent with the effects on DSC trace for the ceramics. 19F MAS-NMR showed fluorine present in Al–F–Ca(n) sites and on heat treatment conversion to fluorapatite. The 29Si MAS-NMR showed a binary distribution of predominantly Q3 and Q4(3Al) species and mullite and residual glass on heat treatment. The 31P MAS-NMR showed pyrophosphate (Q1) groups in the glass and on heat treatment formation of fluorapatite and aluminium phosphate. 27Al MAS-NMR showed the presence of predominantly Al(IV) in the glass and characteristic Al(IV) and Al(VI) sites of mullite and aluminium phosphate as well as residual amorphous material in the ceramics. The details of the structural transformation revealed from the real time measurements have significant implication for manufacturing glass ceramics and its mechanical performance and cannot be deduced based on room temperature measurements after cooling or quenching the material.

In this article we review the ordered micellar and inverse micellar lyotropic liquid-crystalline phases that can be formed by amphiphilic molecules such as lipids and surfactants. We focus first on the self-assembly of amphiphiles into aggregates, and then consider the interfacial curvature and the role of curvature elasticity and packing constraints in determining the allowed structures. We then review the range of ordered micellar and inverse micellar phases that have so far been observed in a variety of surfactant and lipid systems. Finally, we describe certain characteristic properties, such as the epitaxy between phases, and the self-diffusion and electrical conductivity within such ordered micellar phases.

Objectives The main objective is the characterization of the setting reaction in glass ionomer cements (GICs) based on experimental glasses using the 27 Al magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy in order to understand the crosslinking process during the setting reaction. Methods Three types of GICs which are based on fluoro-alumino-silicate glasses (LG125, ART10, and LG26Sr) were studied using 27 Al MAS-NMR to monitor the setting reaction of the cements. Results The result showed clearly the formation of six coordinate, aluminium Al(VI), that crosslink the carboxyl groups in the PAA. The deconvolution study was performed to quantify the amount of each Al species in the cements. The finding showed that composition of original glass has a substantial effect on the setting behavior of the cements. Significance Our data demonstrate that the setting reaction of GICs can be followed by 27 Al MAS-NMR spectroscopy discovering the conversion of Al(IV) to Al(VI). Considerable amount of the five coordinate aluminium, Al(V), species was found in the cements aged up to one year. The presence of phosphorus has a strong influence on the setting reaction. The formation of Al–O–P species was postulated to be present in the cement.

Ternary phase diagrams have been shown to be very useful in understanding the phenomena of lipid rafts. Recently a comprehensive ternary phase diagram for DPPC-d62/DOPC/Chol using static 2H-NMR has been reported [S. L. Veatch, O. Soubias, S. L. Keller, and K. Gawrisch Proceedings of the National Academy of Sciences of the United States of America, 2007, 104, 17650–17655]. However, it is often difficult to interpret these ternary phase diagrams as there are many possible ambiguities, in particular, the extent of the gel(so)–Lo–Lα(ld) three phase region and the clear demarcation between the gel(so) and Lo phase. Here we examine the canonical model lipid raft system by a multinuclear approach using 2H static and 13C, 31P Magic Angle Spinning (MAS) NMR. By using deuterated DPPC (DPPC-d62) it is possible to examine changes in the methylene chain order parameters of the saturated lipid whilst changing the ratio of saturated to unsaturated phospholipid. From these data it is possible to propose the existence at low temperatures (

The effect of the variation in phosphate (P2O5) content on the structure of two series of bioactive glasses in the quaternary system SiO2–Na2O–CaO–P2O5 was studied. The first series (I) was a simple substitution of P2O5 for SiO2 keeping the Na2O:CaO ratio fixed (1.00:0.87). The second series was designed to ensure charge neutrality in the orthophosphate ( PO 4 3 - ) , therefore as P2O5 was added the Na2O and CaO content was varied to provide sufficient Na+ and Ca2+ cations to charge balance the orthophosphate present. The glass network connectivity (NC) was calculated for each glass and a modification for the presence of a separate P2O5 phase was included (NC′). 31P and 29Si magic-angle-spinning nuclear magnetic resonance (MAS-NMR) spectroscopy was performed on glass series I and II to determine the structural units present and their relation to glass properties. 31P MAS-NMR spectra of series I resulted in a broad resonance around 9 ppm corresponding to orthophosphate in an amorphous environment. The 9.25 mol% P2O5 glass shown to be partially crystalline by X-ray diffraction was heat treated, and the 31P MAS-NMR spectrum showed a sharp peak around 3 ppm corresponding to calcium orthophosphate or sodium pyrophosphate and overlapping broader peaks at 8.5, 10.5 and 14 ppm possibly corresponding to two mixed calcium–sodium orthophosphate phases and amorphous sodium orthophosphate respectively. 31P MAS-NMR spectra of series II resulted in a broad resonance around 10.5 ppm corresponding to orthophosphate in an amorphous environment. 29Si MAS-NMR spectra of glasses from series I showed a shift in the resonance peak from around −78 to −86 ppm indicating an increase in Q3 species in the glass and a reduction in Q2 with phosphate addition confirming the presence of orthophosphate. The heat treated sample showed a sharp 29Si-NMR resonance at −88 ppm, indicating a crystalline Q2 six-membered combeite (Na2O · 2CaO · 3SiO2) silicate-type phase, which was confirmed by powder X-ray diffraction. 29Si MAS-NMR spectra of glasses from series II showed no shift in the resonance at around −78 ppm across the series, confirming an orthophosphate environment.

Fluoride is an important mineral for hard tissues in the body and appropriate fluoride exposure and usage are beneficial to bone and tooth integrity. Fluoride increases both bone density and bone mass due to stimulation of bone formation and it is used as a treatment for osteoporosis. Bioactive glasses have the capacity to form an intimate bond with living bone tissue due to formation of a mixed hydroxycarbonate apatite layer (HCA) in vitro and in vivo. This makes fluoride-containing bioactive glasses attractive biomaterials. In order to design fluoride-containing bioactive glasses, we need to understand the role of fluorine within the glass structure. A series of bioactive glasses with increasing fluoride content was prepared by a melt-quench route. Characterisation included differential scanning calorimetry (DSC), density measurements, MASNMR spectroscopy and studies in simulated body fluid (SBF). DSC results showed a linear decrease in glass transition temperature (Tg) with increasing amounts of fluoride. Density of the glasses increased with increasing amounts of fluoride. This may indicate an expansion of the silicate glass network accompanying incorporation of CaF2. 19F MAS-NMR spectroscopy showed broad peaks at chemical shifts between -135 and -120 ppm. As sodium fluoride gives a chemical shift of -223 ppm and calcium fluoride of -108 ppm, this indicated possible formation of mixed calcium sodium fluoride species. HCA and calcium phosphate layers were found on the glasses after one week of immersion in SBF showing the bioactivity of the glass series.

Fluorine containing calcium aluminosilicate glasses are widely used for a number of technological applications including dental cements, mould fluxes in steel making and in a variety of glass-ceramic systems. Despite of their importance these systems remain quite poorly understood with respect to their composition. To address this question a glass composition corresponding to the equimolar binary system anorthite−fluorite (Ca2Al2Si2O8−CaF2) was chosen as a base point for two series of compositions. One of the series is designed on the anorthite stoichiometry and considered as classically charge balanced. Another series starts from the fluorine free composition of the anorthite−lime (Ca2Al2Si2O8−CaO) stoichiometry and, therefore, is characterized by a disrupted network with at least one non-bridging oxygen (NBO) attached to silicon. A multinuclear 19F, 27Al, 29Si solid state NMR study of the glasses was undertaken. It is shown that in both series fluorine is predominantly coordinated by calcium, F−Ca(n), and in addition interacts with aluminium forming Al−F−Ca(n) complexes, where n denotes the number of first neighbouring calcium cations. Small amounts of high coordinated aluminium grows with increasing fluoride content in both glass series. However, the high coordinated aluminium may not be solely due to the formation of the Al−F−Ca(n) complexes. Glasses of the first series displayed systematic upfield shift of 29Si NMR resonance while substituting fluoride for oxide, starting from the fluorine free composition. This upfield shift is interpreted as the lack of cations in the network, due to formation of the F−Ca(n), which drives silicon network to polymerize toward a higher Qn structure. Contrary to the first series, the 29Si NMR resonance remains constant for fluorine containing compositions of the second series but differs downfield from the initial anorthite glass. The latter is explained by the excess of cations in the network due to addition of the fluorite resulting in formation of NBO on the silicon. Binding of fluorine with silicon is considered negligible in these systems. Thus, fluorine and calcium both define the degree of network polymerization and are considered as a cause for the changes in silicon and aluminium networks.

The role of cholesterol (Chol) in promoting lamellar phase formation in mixtures with 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (Lyso-PPC) in excess water was investigated using multinuclear solid-state NMR and X-ray scattering. It was found that mixtures containing Chol and Lyso-PPC form a liquid-ordered (Lo) lamellar phase over a range of temperatures and concentrations, as previously observed in mixtures of Chol with various diacylphospholipids. The maximum quadrupolar splitting of the 2H-NMR powder patterns for samples containing per-deuterated Lyso-PPC were 40–50 kHz which is strongly indicative of an Lo phase. This evidence was supported by wide angle X-ray scattering data which showed a characteristic diffuse peak centred at 4.2 A. The Lo phase coexists with an isotropic Lyso-PPC phase at Chol concentrations up to 70 mol% Chol, and with Chol crystals at Chol concentrations above this value. Below 70 mol% Chol, an increase in the concentration of Chol in the system caused a corresponding increase in the proportion of the Lo phase present compared with the amount of isotropic Lyso-PPC. The chemical-shift anisotropy (CSA) of the static 31P-NMR spectra of the Lo phase showed the symmetry of a lamellar phase, but the linewidth, Δσ, was much narrower than CSA powder patterns obtained for diacylphospholipids in similar conditions, being ∼20 ppm as opposed to ∼40 ppm, respectively.

This talk will outline novel microfluidic strategies for biomembrane engineering that are capable of fabricating vesicles [1], droplet interface bilayer networks [2], multisomes [3] and artificial tissues [4] 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 [1] and study the engineering rules that regulate membrane mediated protein-protein interactions [5]. In addition, these technologies are enabling the construction of biological machines capable of acting as micro-reactors [6], environmental sensors and smart delivery vehicles [5] 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 development of multi-step enzymatic signalling cascades integrated into artificial cells leading to in-situ chemical synthesis [7]. The ability to compartmentalise synthetic cells is opening up the possibility of increasing our understanding of how this phenomena controls signal transduction and biological function in real cells by allowing us to manufacture protocells that more accurately capture the spatio-temporal structures of real cells. Finally we will present the development of droplet based artificial tissues that can be used to generate display materials based on biological components [4].

Cationic amphiphilic drugs (CADs), such as haloperidol, are able to translocate through biological membrane bilayers via a chemically activated degradation of the phospholipid fabric of the membrane, which may constitute a third type of drug translocation process. We present evidence that this effect is dependent on the drug formulation. The choice of drug counterion is shown to influence the rate of bilayer hydrolysis, leading either to promotion of the reaction or the drug's precipitation via a counterion condensation process.

The nature of the bilayer motif coupled with the ability of lipids and proteins to diffuse freely through this structure is crucial to the viability of cells and their ability to compartmentalize domains contained therein. It seems surprising to find then that biological as well as model membranes exist in a dynamic state of mechanical stress. The stresses within such membranes are surprisingly large, typically reaching up to 50 atm (1 atm=101.325 kPa) at the core of the membrane and vary as a function of depth. The uneven distribution of lateral pressures within monolayer leaflets causes them to bend away from or towards the water interface. This can result in the formation of complex, self-assembled mesophases, many of which occur in vivo. Our knowledge of the principles underlying membrane mechanics has reached the point where we are now able to manipulate them and create nano-structures with reasonable predictability. In addition, they can be used both to explain and control the partitioning of amphipathic proteins on to membranes. The dependence of the dynamics of membrane-bound proteins and the chemical reactivity of amphipathic drug molecules on membrane stresses suggests that Nature itself takes advantage of this. Understanding and manipulating these internal forces will be a key element in creating self-assembled, biocompatible, nanoscale cell-like systems.

In the present study we report the results of 29Si, 27Al, 31P and 19F magic angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR) of 4.5SiO2–3Al2O3–1.5P2O5–(5−z)CaO–zCaF2 glasses with z = 0–3 to elucidate the effect of fluoride content on the glass structure. The 29Si MAS-NMR spectra gave a chemical shift of about −90 ppm corresponding to Q3(3Al) and Q4(3Al). The 27Al MAS-NMR showed a large broad central peak around 50 ppm, which is assigned to four-coordinated Al linked via oxygen to P. A shoulder around 30 ppm and a small peak at about 0 to −10 ppm appeared in the 27Al MAS-NMR spectra of the glasses on increasing the fluoride content assigned to five-coordinated and six-coordinated Al species, respectively. The 31P MAS-NMR spectra indicated the presence of Al–O–P bonds. The 31P chemical shift decreased with increasing fluoride content as a result of calcium being complexed with fluoride. This resulted in a reduction of the number of available cations to charge balance non bridging oxygens in phosphorus and an increase in the number of Al–O–P bonds being formed, instead. The 19F spectra indicated the presence of Al–F–Ca(n) and F–Ca(n) species in all the glasses containing fluoride as well as an additional Si–F–Ca(n) species in the glasses with higher fluoride content.

Phase separation in ternary model membranes is known to occur over a range of temperatures and compositions and can be induced by increasing hydrostatic pressure. We have used small angle X-ray scattering (SAXS) to study phase separation along pre-determined tie lines in dioleoylphosphatidylcholine (DOPC), dipalmitoylphosphatidylcholine (DPPC) and cholesterol (CHOL) mixtures. We can unequivocally distinguish the liquid ordered (Lo) and liquid disordered (Ld) phases in diffraction patterns from biphasic mixtures and compare their lateral compressibility. The variation of tie line endpoints with increasing hydrostatic pressure was determined, at atmospheric pressure and up to 100 MPa. We find an extension and shift of the tie lines towards the DOPC rich region of the phase diagram at increased pressure, this behaviour differs slightly from that reported for decreasing temperature.

Conditions are described for the preparation of cholesterol with (17)O and (18)O 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 enrichment90% 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.

Whereas spatial organisation of function is ubiquitous in biology, it has been lacking in artificial cells. We rectify this by using multi-compartment vesicles as chassis for artificial cells, allowing distinct biological processes to be isolated in space. This is demonstrated by in vitro synthesis of two proteins in predefined vesicle regions.