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31 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I07-Surface & interface diffraction	Suspended phospholipid bilayers: A new biological membrane mimetic Sophie E. Ayscough , Luke A. Clifton , Maximilian W. A. Skoda , Simon Titmuss Journal Of Colloid And Interface Science 633, 1002 - 1011 DOI: 10.1016/j.jcis.2022.11.148 Diamond Proposal Number(s): [22995] Open Access Show Abstract ▼ Abstract: Hypothesis: The attractive interaction between a cationic surfactant monolayer at the air–water interface and vesicles, incorporating anionic lipids, is sufficient to drive the adsorption and deformation of the vesicles. Osmotic rupture of the vesicles produces a continuous lipid bilayer beneath the monolayer. Experimental: Specular neutron reflectivity has been measured from the surface of a purpose-built laminar flow trough, which allows for rapid adsorption of vesicles, the changes in salt concentration required for osmotic rupture of the adsorbed vesicles into a bilayer, and for neutron contrast variation of the sub-phase without disturbing the monolayer. Findings: The neutron reflectivity profiles measured after vesicle addition are consistent with the adsorption and flattening of the vesicles beneath the monolayer. An increase in the buffer salt concentration results in further flattening and fusion of the adsorbed vesicles, which are ruptured by a subsequent decrease in the salt concentration. This process results in a continuous, high coverage, bilayer suspended 11 Å beneath the monolayer. As the bilayer is not constrained by a solid substrate, this new mimetic is well-suited to studying the structure of lipid bilayers that include transmembrane proteins.	Mar 2023
B21-High Throughput SAXS	New insights on the release and self-healing model of stimuli-sensitive liposomes Olga V. Zaborova , Vadim A. Timoshenko , Corinne Nardin , Sergey K. Fillipov Journal Of Colloid And Interface Science 12 DOI: 10.1016/j.jcis.2023.02.099 Diamond Proposal Number(s): [12411] Show Abstract ▼ Abstract: The mixing of conventional and pH-sensitive lipids was exploited to design novel stimuli-responsive liposomes (fliposomes) that could be used for smart drug delivery. We deeply investigated the structural properties of the fliposomes and revealed the mechanisms that are involved in a membrane transformation during a pH change. From ITC experiments we observed the existence of a slow process that was attributed to lipid layers arrangement with changing pH. Moreover, we determined for the first time the pKa value of the trigger-lipid in an aqueous milieu that is drastically different from the methanol-based values reported previously in the literature. Furthermore, we studied the release kinetics of encapsulated NaCl and proposed a novel model of release that involves the physical fitting parameters that could be extracted from the release curves fitting. We have obtained for the first time, the values of pores self-healing times and were able to trace their evolution with changing pH, temperature, the amount of lipid-trigger.	Feb 2023
	The interaction of styrene maleic acid copolymers with phospholipids in langmuir monolayers, vesicles and nanodiscs; a structural study Stephen C. I. Hall , Cecilia Tognoloni , Richard A. Campbell , Joanna Richens , Paul O'Shea , Ann E. Terry , Gareth J. Price , Tim R. Dafforn , Karen J. Edler , Thomas Arnold Journal Of Colloid And Interface Science 8 DOI: 10.1016/j.jcis.2022.03.102 Open Access Show Abstract ▼ Abstract: Hypothesis: Self-assembly of amphipathic styrene maleic acid copolymers with phospholipids in aqueous solution results in the formation of ‘nanodiscs’ containing a planar segment of phospholipid bilayer encapsulated by a polymer belt. Recently, studies have reported that lipids rapidly exchange between both nanodiscs in solution and external sources of lipids. Outstanding questions remain regarding details of polymer-lipid interactions, factors influencing lipid exchange and structural effects of such exchange processes. Here, the dynamic behaviour of nanodiscs is investigated, specifically the role of membrane charge and polymer chemistry. Experiments: Two model systems are investigated: fluorescently labelled phospholipid vesicles, and Langmuir monolayers of phospholipids. Using fluorescence spectroscopy and time-resolved neutron reflectometry, the membrane potential, monolayer structure and composition are monitored with respect to time upon polymer and nanodisc interactions. Findings: In the presence of external lipids, polymer chains embed throughout lipid membranes, the extent of which is governed by the net membrane charge. Nanodiscs stabilised by three different polymers will all exchange lipids and polymer with monolayers to differing extents, related to the properties of the stabilising polymer belt. These results demonstrate the dynamic nature of nanodiscs which interact with the local environment and are likely to deposit both lipids and polymer at all stages of use.	Mar 2022
I13-2-Diamond Manchester Imaging	New type of pore-snap-off and displacement correlations in imbibition Kamaljit Singh , Tom Bultreys , Ali Q. Raeini , Mosayeb Shams , Martin J. Blunt Journal Of Colloid And Interface Science 40 DOI: 10.1016/j.jcis.2021.11.109 Diamond Proposal Number(s): [11587] Show Abstract ▼ Abstract: Hypothesis: Imbibition of a fluid into a porous material involves the invasion of a wetting fluid in the pore space through piston-like displacement, film and corner flow, snap-off and pore bypassing. These processes have been studied extensively in two-dimensional (2D) porous systems; however, their relevance to three-dimensional (3D) natural porous media is poorly understood. Here, we investigate these pore-scale processes in a natural rock sample using time-resolved 3D (i.e., four-dimensional or 4D) X-ray imaging. Experiments: We performed a capillary-controlled drainage-imbibition experiment on an initially brine-saturated carbonate rock sample. The sample was imaged continuously during imbibition using 4D X-ray imaging to visualize and analyze fluid displacement and snap-off processes at the pore-scale. Findings: We discover a new type of snap-off that occurs in pores, resulting in the entrapment of a small portion of the non-wetting phase in pore corners. This contrasts with previously-observed snap-off in throats which traps the non-wetting phase in pore centers. We relate the new type of pore-snap-off to the pinning of fluid-fluid interfaces at rough surfaces, creating contact angles close to 90°. Subsequently, we provide correlations for displacement events as a function of pore-throat geometry. Our findings indicate that having a small throat does not necessarily favor snap-off: the key criterion is the throat radius in relation to the pore radius involved in a displacement event, captured by the aspect ratio.	Nov 2021
I22-Small angle scattering & Diffraction	Unraveling agglomeration and deagglomeration in aqueous colloidal dispersions of very small tin dioxide nanoparticles Viktor Mackert , Martin A. Schroer , Markus Winterer Journal Of Colloid And Interface Science 112 DOI: 10.1016/j.jcis.2021.10.194 Diamond Proposal Number(s): [16515] Show Abstract ▼ Abstract: Hypothesis: Understanding deagglomeration, agglomerate formation and structure for very small nanoparticles (NPs), due to their more facile agglomeration, is critical for processing or tailoring agglomerates for nanostructured materials. We propose that by controlling and fine-tuning the interplay of agglomeration (colloidal interaction) and deagglomeration (hydrodynamic forces), the design of agglomerate size, microstructure and morphology is possible even for very small NPs. Experiments: Here, we investigate very small SnO2 NPs (10 nm) generated in the gas phase as model system. Small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) are used to study dispersions in aqueous media across the entire pH range (2 – 12) at various NaCl concentrations treated with ultrasound. Parallel to size and size distribution, agglomerate morphology and microstructure are analyzed by means of the mass fractal dimension, dm and modeled with ab initio shape simulations. The critical coagulation concentration (CCC) is determined for the alkaline region where the SnO2 NPs are highly charged. Findings: Quantitative analysis of SAXS and DLS data reveals that size and size distribution of the agglomerates depend similarly on the electrostatic interaction influenced by pH and salinity as observed by the zeta potential. In contrast dm is mainly influenced by the salt concentration. Ab initio shape simulations support these experimental findings.	Nov 2021
B21-High Throughput SAXS	Balanced lipase interactions for degradation-controlled paclitaxel release from lipid cubic phase formulations Michele Dully , Shayon Bhattacharya , Vivek Verma , David Murray , Damien Thompson , Tewfik Soulimane , Sarah P. Hudson Journal Of Colloid And Interface Science 31 DOI: 10.1016/j.jcis.2021.09.024 Diamond Proposal Number(s): [24926] Open Access Show Abstract ▼ 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.	Sep 2021
B23-Circular Dichroism	Modelling the adsorption of proteins to nanoparticles at the solid-liquid interface Mikhail Soloviev , Giuliano Siligardi , Danilo Roccatano , Enrico Ferrari Journal Of Colloid And Interface Science 162 DOI: 10.1016/j.jcis.2021.07.072 Diamond Proposal Number(s): [27024] Show Abstract ▼ 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.	Jul 2021
I22-Small angle scattering & Diffraction	Effects of ethylene oxide chain length on crystallization of polysorbate 80 and its related compounds Tania K. Lind , Emelie J. Nilsson , Benjamin Wyler , Dieter Scherer , Tatyana Skansberger , Maxim Morin , Vitaly Kocherbitov , Johan Engblom Journal Of Colloid And Interface Science 592, 468 - 484 DOI: 10.1016/j.jcis.2021.01.065 Diamond Proposal Number(s): [22299] Open Access Show Abstract ▼ 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.	Jun 2021
I07-Surface & interface diffraction	Heads or tails: Nanostructure and molecular orientations in organised erucamide surface layers Dajana Gubala , Laura Fox , Robert Harniman , Hadeel Hussain , Eric Robles , Meng Chen , Wuge H. Briscoe Journal Of Colloid And Interface Science 590, 506 - 517 DOI: 10.1016/j.jcis.2021.01.087 Diamond Proposal Number(s): [22176] Show Abstract ▼ 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%.	May 2021
B18-Core EXAFS	Fe(II) interaction with cement phases: Method development, wet chemical studies and X-ray absorption spectroscopy A. Mancini , E. Wieland , G. Geng , B. Lothenbach , B. Wehrli , R. Dähn Journal Of Colloid And Interface Science DOI: 10.1016/j.jcis.2020.11.085 Diamond Proposal Number(s): [21670] Open Access Show Abstract ▼ 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.	Nov 2020

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