B21-High Throughput SAXS
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Diamond Proposal Number(s):
[24926]
Open Access
Abstract: Lipid cubic phase (LCP) formulations enhance the intestinal solubility and bioavailability of hydrophobic drugs by reducing precipitation and facilitating their mass transport to the intestinal surface for absorption. LCPs with an ester linkage connecting the acyl chain to the glycerol backbone (monoacylglycerols), are susceptible to chemical digestion by several lipolytic enzymes including lipases, accelerating the release of hydrophobic agents from the lipid bilayers of the matrix. Unlike regular enzymes that transform soluble substrates, lipolytic enzymes act at the interface of water and insoluble lipid. Therefore, compounds that bind to this interface can enhance or inhibit the activity of enzymes to varying extent. Here, we explore how the lipolysis rate can be tuned by the interfacial interaction of porcine pancreatic lipase with monoolein LCPs containing a known lipase inhibitor, tetrahydrolipstatin. Release of the Biopharmaceutical Classification System (BCS) class IV drug, paclitaxel, from the inhibitor-modified LCP was examined in the presence of lipase and its effectors colipase and calcium. By combining experimental dynamic digestion studies, thermodynamic measurements and molecular dynamics simulations of the competitive inhibition of lipase by tetrahydrolipstatin, we reveal the role and mode of action of lipase effectors in creating a precisely-balanced degradation-controlled LCP release system for the poorly soluble paclitaxel drug.
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Sep 2021
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B23-Circular Dichroism
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Diamond Proposal Number(s):
[27024]
Abstract: Hypothesis: We developed a geometrical model to determine the theoretical maximum number of proteins that can pack as a monolayer surrounding a spherical nanoparticle. We applied our new model to study the adsorption of receptor binding domain (RBD) of the SARS-CoV-2 spike protein to silica nanoparticles. Due to its abundance and extensive use in manufacturing, silica represents a reservoir where the virus can accumulate. It is therefore important to study the adsorption and the persistence of viral components on inanimate surfaces. Experiments: We used previously published datasets of nanoparticle-adsorbed proteins to validate the new model. We then used integrated experimental methods and Molecular Dynamics (MD) simulations to characterise binding of the RBD to silica nanoparticles and the effect of such binding on RBD structure. Findings: The new model showed excellent fit with existing datasets and, combined to new RBD-silica nanoparticles binding data, revealed a surface occupancy of 32% with respect to the maximum RBD packing theoretically achievable. Up to 25% of RBD’s secondary structures undergo conformational changes as a consequence of adsorption onto silica nanoparticles. Our findings will help developing a better understanding of the principles governing interaction of proteins with surfaces and can contribute to control the spread of SARS-CoV-2 through contaminated objects.
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Jul 2021
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[22299]
Open Access
Abstract: As a result of the synthesis protocol polyoxyethylene sorbitan monooleate (polysorbate 80, PS80) is a highly complex mixture of compounds. PS80 was therefore separated into its main constituents, e.g. polyoxyethylene isosorbide esters and polyoxyethylene esters, as well as mono- di- and polyesters using preparative high-performance liquid chromatography. In this comprehensive study the individual components and their ethoxylation level were verified by matrix assisted laser desorption/ionization time-of-flight and their thermotropic behavior was analyzed using differential scanning calorimetry and X-ray diffraction. A distinct correlation was found between the average length of the ethylene oxide (EO) chains in the headgroup and the individual compounds’ ability to crystallize. Importantly, a critical number of EO units required for crystallization of the headgroup was determined (6 EO units per chain or 24 per molecule). The investigation also revealed that the hydrocarbon tails only crystallize for polyoxyethylene sorbitan esters if saturated. PS80 is synthesized by reacting with approximately 20 mol of EO per mole of sorbitol, however, the number of EO units in the sorbitan ester in commercial PS80 products is higher than the expected 20 (5 EO units per chain). The complex behavior of all tested compounds revealed that if the amount of several of the linear by-products is reduced, the number of EO units in the chains will stay below the critical number and the product will not be able to crystallize by the EO chains.
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Jun 2021
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[22176]
Abstract: Hypothesis: Despite the widespread industrial usage of erucamide as a slip additive to modify polymer surface properties, a controversy appears to have persisted regarding the nanostructure of erucamide surface layers, particularly the molecular orientation at the outermost layer. The erucamide nanostructure and molecular orientation, along with its surface coverage, hydrophobicity, and adhesive response, can be tuned by simply varying the erucamide concentration in the solution from which the spin coated layer is prepared. Experiments: Synchrotron X-ray reflectivity (XRR) allowed a comprehensive characterisation of the out-of-plane structural parameters (e.g. molecular packing and thickness) of the erucamide layers prepared via spin coating from nonaqueous solution on silica. Complementary Atomic Force Microscopy (AFM) imaging with high lateral resolution revealed localised in-plane structures. Contact angle measurements provided information on the wettability of erucamide-coated surfaces. Peak Force Quantitative Nanomechanical Mapping (QNM) allowed a correlation between the erucamide nanostructure with the surface nanomechanical properties (i.e. adhesive response). Findings: Our results reveal erucamide surface nanostructures on silica as patchy monolayers, isolated circular bilayers/rounded rectangle-like aggregates and overlapping plate-like multilayers as the erucamide concentration in the spin coating solution was varied. In all the cases, XRR and AFM results were consistent with the picture that the erucamide tails were oriented outwards. The QNM adhesion force mapping of all the observed morphologies also supported this molecular orientation at the outermost erucamide monolayer. The wettability study further confirmed this conclusion with the observed increase in the surface hydrophobicity and coverage upon increasing erucamide concentration, with the macroscopic water contact angle θ = 92.9° ± 2.9° at the highest erucamide concentration of 2 wt%.
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May 2021
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B18-Core EXAFS
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Diamond Proposal Number(s):
[21670]
Open Access
Abstract: Fe(II) interaction with cement phases was studied by means of co-precipitation and sorption experiments in combination with X-ray absorption fine structure (XAFS) spectroscopy. Oxidation of Fe(II) was fast in alkaline conditions and therefore, a methodology was developed which allowed Fe(II) to be stabilised in the sorption experiments and to prepare samples for spectroscopy. X-ray diffraction (XRD) of the co-precipitation samples showed uptake of a small portion of Fe(II) by calcium-silicate-hydrates (C-S-H) in the interlayer indicated by an increase in the interlayer spacing. Fe(II) incorporation by AFm phases was not indicated. Wet chemical experiments using 55Fe radiotracer revealed linear sorption of Fe(II) irrespective of the Ca/Si ratio of C-S-H and equilibrium pH. The Kd values for Fe(II) sorption on C-S-H are more than three orders of magnitude lower as compared to Fe(III), while they are comparable to those of other bivalent metal cations. XAFS spectroscopy showed Fe(II) binding by C-S-H in an octahedral coordination environment. The large number of neighbouring atoms rules out the formation of a single surface-bound Fe(II) species. Instead the data suggest presence of Fe(II) in a structurally bound entity. The data from XRD and XAFS spectroscopy suggests the presence of both surface- and interlayer-bound Fe(II) species.
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Nov 2020
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I13-2-Diamond Manchester Imaging
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Open Access
Abstract: Hypothesis: We define contact angles, h, during displacement of three fluid phases in a porous medium using energy balance, extending previous work on two-phase flow. We test if this theory can be applied to quantify the three contact angles and wettability order in pore-scale images of three-phase displacement. Theory: For three phases labelled 1, 2 and 3, and solid, s, using conservation of energy ignoring viscous dissipation ðDa1s cos h12 Da12 /j12 DS1 Þr12 1⁄4 ðDa3s cos h23 þ Da23 /j23 DS3 Þr23 þ Da13 r13 , where / is the porosity, r is the interfacial tension, a is the specific interfacial area, S is the saturation, and j is the fluid–fluid interfacial curvature. D represents the change during a displacement. The third contact angle, h13 can be found using the Bartell-Osterhof relationship. The energy balance is also extended to an arbitrary number of phases.
Findings: X-ray imaging of porous media and the fluids within them, at pore-scale resolution, allows the difference terms in the energy balance equation to be measured. This enables wettability, the contact angles, to be determined for complex displacements, to characterize the behaviour, and for input into pore-scale models. Two synchrotron imaging datasets are used to illustrate the approach, comparing the flow of oil, water and gas in a water-wet and an altered-wettability limestone rock sample. We show that in the water-wet case, as expected, water (phase 1) is the most wetting phase, oil (phase 2) is inter- mediate wet, while gas (phase 3) is most non-wetting with effective contact angles of h12 % 48 and h13 % 44, while h23 1⁄4 0 since oil is always present in spreading layers. In contrast, for the altered-wettability case, oil is most wetting, gas is intermediate-wet, while water is most non-wetting with con- tact angles of h12 1⁄4 134 $ 10;h13 1⁄4 119 $ 10, and h23 1⁄4 66 $ 10.
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Sep 2020
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[19013]
Open Access
Abstract: Surfactant-mediated chemical routes allow one to synthesize highly engineered shape- and size-controlled nanocrystals. However, the occurrence of capping agents on the surface of the nanocrystals is undesirable for selected applications. Here, a novel approach to the production of shape-controlled nanocrystals which exhibit high thermal stability is demonstrated. Ceria nanocubes obtained by surfactant-mediated synthesis are embedded inside a highly porous silica aerogel and thermally treated to remove the capping agent. Powder X-ray Diffraction and Scanning Transmission Electron Microscopy show the homogeneous dispersion of the nanocubes within the aerogel matrix. Remarkably, both the size and the shape of the ceria nanocubes are retained not only throughout the aerogel syntheses but also upon thermal treatments up to 900 °C, while avoiding their agglomeration. The reactivity of ceria is measured by in situ High-Energy Resolution Fluorescence Detected - X-ray Absorption Near Edge Spectroscopy at the Ce L3 edge, and shows the reversibility of redox cycles of ceria nanocubes when they are embedded in the aerogel. This demonstrates that the enhanced reactivity due to their prominent {100} crystal facets is preserved. In contrast, unsupported ceria nanocubes begin to agglomerate as soon as the capping agent decomposes, leading to a degradation of their reactivity already at 275 °C.
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Sep 2020
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B21-High Throughput SAXS
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Diamond Proposal Number(s):
[23247]
Abstract: Multilamellar wall vesicles (MLWV) are an interest class of polyelectrolyte-surfactant complexes (PESCs) for the wide applications ranging from house-care to biomedical products. If MLWV are generally obtained by a polyelectrolyte-driven vesicle agglutination under pseudo-equilibrium conditions, the resulting phase is often a mixture of more than one structure. In this work, we show that MLWV can be massively and reproductively prepared from a recently developed method involving a pH-stimulated phase transition from a complex coacervate phase (Co). We employ a biobased pH-sensitive microbial glucolipid biosurfactant in the presence of a natural, or synthetic, polyamine (chitosan, poly-L-Lysine, polyethylene imine, polyallylamine). In situ small angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) show a systematic isostructural and isodimensional transition from the Co to the MLWV phase, while optical microscopy under polarized light experiments and cryo-TEM reveal a massive, virtually quantitative, presence of MLWV. Finally, the multilamellar wall structure is not perturbed by filtration and sonication, two typical methods employed to control size distribution in vesicles. In summary, this work highlights a new, robust, non-equilibrium phase-change method to develop biobased multilamellar wall vesicles, promising soft colloids with applications in the field of personal care, cosmetics and pharmaceutics among many others.
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Jul 2020
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Andi
Di
,
Julien
Schmitt
,
Kun
Ma
,
Marcelo A.
Da Silva
,
Naomi S.
Elstone
,
Najet
Mahmoudi
,
Peixun
Li
,
Adam
Washington
,
Zi
Wang
,
R. John
Errington
,
Karen J.
Edler
Abstract: Hypothesis: Polyoxometalates (POMs) are metal oxygen clusters with a range of interesting magnetic and catalytic properties. POMs with attached hydrocarbon chains show amphiphilic behaviour so we hypothesised that mixtures of a non-ionic surfactant and anionic surfactants with a polyoxometalate cluster as headgroup would form mixed micelles, giving control of the POM density in the micelle, but which would differ in size and shape from micelles formed by the individual surfactants. Due to the high charge and large size of the POM, we suggested that these would be nonideal mixtures due to the complex interactions between the two types of surfactants. The nonideality and the micellar composition may be quantified using regular solution theory. With supplementary information provided by small-angle neutron scattering, an understanding of this unusual binary surfactant system can be established. Experiments: A systematic study was performed on mixed surfactant systems containing polyoxometalate-headed amphiphiles (K10[P2W17O61OSi2(CnH2n+1)2], abbreviated as P2W17-2Cn, where n = 12, 14 or 16) and hexaethylene glycol monododecyl ether (C12EO6). Critical micelle concentrations (CMCs) of these mixtures were measured and used to calculate the interaction parameters based on regular solution theory, enabling prediction of micellar composition. Predictions were compared to micelle structures obtained from small angle neutron scattering (SANS). A phase diagram was also established. Findings: The CMCs of these mixtures suggest unusual unfavourable interactions between the two species, despite formation of mixed micelles. Micellar compositions obtained from SANS concurred with those calculated using the averaged interaction parameters for P2W17-2Cn/C12EO6 (n = 12 and 14). We attribute the unfavourable interactions to a combination of different phenomena: counterion-mediated interactions between P2W17 units and the unfolding of the ethylene oxide headgroups of the nonionic surfactant, yet micelles still form in these systems due to the hydrophobic interactions between surfactant tails.
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Jun 2020
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Abstract: Hypothesis: Extracellular Vesicles (EVs) are natural nanosized lipid vesicles involved in most intercellular communication pathways. Given their nature, they represent natural cell membrane models, with intermediate complexity between real and synthetic lipid membranes. Here we compare EVs-derived (EVSLB) and synthetic Supported Lipid Bilayers (SLBs) in the interaction with cationic superparamagnetic iron oxide nanoparticles (SPIONs). The aim is twofold: (i) exploit SPIONs as nanometric probes to investigate the features of EVSLBs as novel biogenic platforms; (ii) contribute at improving the knowledge on the behavior of SPIONs with biological interfaces. Experiments: Quartz Crystal Microbalance, X-ray Reflectivity, Grazing-incidence Small-angle X-ray Scattering, Atomic Force Microscopy, Confocal Microscopy data on SPIONs-EVSLB were systematically compared to those on SPIONs challenging synthetic SLBs, taken as references. Findings: The ensemble of experimental results highlights the much stronger interaction of SPIONs with EVSLBs with respect to synthetic SLBs. This evidence strongly supports the hypotheses on the peculiar structure of EVSLBs, with cushioned non-flat areas and extended exposed surface; in addition, it suggests that these features are relevant in the response of biogenic membranes to nano-objects. These findings contribute to the fundamental knowledge on EVSLBs, key for their development both as biomimetic membranes, or as platforms for biomedical applications.
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Jun 2020
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