Browsing by Author "Clulow, AJ"
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- ItemBioSAXS: the future of solution scattering at the Australian Synchrotron(Australian Nuclear Science and Technology Organisation, 2021-11-25) Kamma-Lorger, C; Venkatesan, S; Conesa- Zamora, G; Barnsley, L; Clulow, AJ; Jensen, B; Hamedi, N; Samardzic-Boban, V; Roy, CBioSAXS is one of the new beamlines to be constructed at the Australian Synchrotron within the BRIGHT program. The beamline is currently under construction and it is scheduled to phase into user operations in mid-late 2022. BioSAXS will be a high-flux (~5 x 1014 ph/sec) small angle X-ray scattering beamline dedicated to all sorts of solution scattering including dispersions, gels and soft matter, covering a variety of disciplines from biology to chemistry and material sciences. The high flux of the beamline will provide enhanced data quality and kinetic resolution, allowing for time-resolved studies on the millisecond timescale, as well as the measurement of weak scatterers and low concentrations that wouldn’t otherwise be possible to measure. The in-vacuum detector system at the end station will provide quick and highly automated camera changes, a q range of ~0.0015 – 3 Å-1 and low background in collected data. The CoFlow, a pioneering development of the Australian Synchrotron, will be the primary autoloading device for high throughput experiments. Other sample environment options will include a stopped-flow and rheometer, temperature-controlled capillary stages, a shear cell as well as a versatile magnetic-array system, optimized for experiments on magnetic nanoparticles used in biomedical applications. The beamline’s sample platform will also accommodate the installation of user equipment. The objective of this presentation is to demonstrate BioSAXS’ final design and capabilities that will allow it to develop into a highly-automated and versatile beamline that can accommodate a widerange of solution scattering experiments, complementing the existing SAXS/WAXS beamline to ensure the world-leading capabilities of the SAXS offering at the Australian Synchrotron. © The Authors
- ItemDetermination of fullerene scattering length density: a critical parameter for understanding the fullerene distribution in bulk heterojunction organic photovoltaic devices(American Chemical Society, 2014-01-27) Clulow, AJ; Armin, A; Lee, KH; Pandey, AK; Tao, C; Velusamy, M; James, M; Nelson, A; Burn, PL; Gentle, IR; Meredith, PFullerene derivatives are commonly used as electron acceptors in combination with (macro)molecular electron donors in bulk heterojunction (BHJ) organic photovoltaic (OPV) devices. Understanding the BHJ structure at different electron donor/acceptor ratios is critical to the continued improvement and development of OPVs. The high neutron scattering length densities (SLDs) of the fullerenes provide effective contrast for probing the distribution of the fullerene within the blend in a nondestructive way. However, recent neutron scattering studies on BHJ films have reported a wide range of SLDs ((3.6–4.4) × 10–6 Å–2) for the fullerenes 60-PCBM and 70-PCBM, leading to differing interpretations of their distribution in thin films. In this article, we describe an approach for determining more precisely the scattering length densities of the fullerenes within a polymer matrix in order to accurately quantify their distribution within the active layers of OPV devices by neutron scattering techniques.© 2014, American Chemical Society.
- ItemImpact of pasteurization on the self-assembly of human milk lipids during digestion(Elsevier Inc on behalf of American Society for Biochemistry and Molecular Biology, 2022-05) Binte Abu Bakar, SY; Salim, M; Clulow, AJ; Hawley, A; Pelle, J; Geddes, DT; Nicholas, KR; Boyd, BJHuman milk is critical for the survival and development of infants. This source of nutrition contains components that protect against infections while stimulating immune maturation. In cases where the mother's own milk is unavailable, pasteurized donor milk is the preferred option. Although pasteurization has been shown to have minimal impact on the lipid and FA composition before digestion, no correlation has been made between the impact of pasteurization on the FFA composition and the self-assembly of lipids during digestion, which could act as delivery mechanisms for poorly water-soluble components. Pooled nonpasteurized and pasteurized human milk from a single donor was used in this study. The evolving FFA composition during digestion was determined using GC coupled to a flame ionization detector. In vitro digestion coupled to small-angle X-ray scattering was utilized to investigate the influence of different calcium levels, fat content, and the presence of bile salts on the extent of digestion and structural behavior of human milk lipids. Almost complete digestion was achieved when bile salts were added to the systems containing high calcium to milk fat ratio, with similar structural behavior of lipids during digestion of both types of human milk being apparent. In contrast, differences in the colloidal structures were formed during digestion in the absence of bile salt because of a greater amount of FFAs being released from the nonpasteurized than pasteurized milks. This difference in FFAs released from both types of human milk could result in varying nutritional implications for infants. © 2022 The Authors. This is an open access article under the CC BY licence
- ItemThe influence of glass transitions on diffusion in OLED stacks(Australian Institute of Nuclear Science and Engineering, 2016-11-29) McEwan, JA; Clulow, AJ; Shaw, PE; Nelson, A; Yepuri, NR; Darwish, TA; Burn, PL; Gentle, IROf all of the organic electronic devices thus far conceived, organic light emitting diodes (OLEDs) have been the most successfully applied in a commercial setting. With OLED displays now available in the television and portable device markets, the appetite for their continued development continues to garner considerable research interest. Optimised OLED device architectures typically comprise a number of organic layers with thicknesses between 10 nm and 100 nm sandwiched between inorganic electrodes. Each of the organic layers used in the device is sequentially deposited in an order that optimises charge transport and capture, and light emission from the devices. The fidelity and stability of these multilayer organic stacks is therefore of paramount importance in determining the efficiencies and operational lifetimes of OLED devices. Neutron reflectometry is a powerful technique for probing the layered structures found within OLEDs by utilising selective deuteration to provide contrast between or within the layers.1–3 Modelling the changes in the neutron reflectivity profiles of the OLED stacks deposited onto smooth substrates allows for the visualisation of changes in the layered structure in a non destructive manner. In this talk we will outline our recent efforts to relate the thermal properties of the organic materials used in OLED devices with their diffusion behaviour under thermal stress. Our collaboration with the National Deuteration Facility has led to the synthesis of a number of previously unobtainable deuterated analogues of semiconducting molecules typically used in OLEDs and that have a range of thermal characteristics.3–5 These molecules were used in time-resolved reflectometry experiments that have allowed us to systematically build up an understanding of the importance of glass transitions for the stability of OLED stacks.
- ItemInfluence of lyophilization and cryoprotection on the stability and morphology of drug-loaded poly(ethylene glycol-b-ε-caprolactone) micelles(MDPI, 2023-04-21) Hussain, MS; Faisal, KS; Clulow, AJ; Albrecht, H; Krasowska, M; Blencowe, APolymeric micelles are promising carriers for the delivery of poorly water-soluble drugs, providing enhanced drug solubility, blood circulation times, and bioavailability. Nevertheless, the storage and long-term stability of micelles in solution present challenges requiring the lyophilization and storage of formulations in the solid state, with reconstitution immediately prior to application. Therefore, it is important to understand the effects of lyophilization/reconstitution on micelles, particularly their drug-loaded counterparts. Herein, we investigated the use of β-cyclodextrin (β-CD) as a cryoprotectant for the lyophilization/reconstitution of a library of poly(ethylene glycol-b-ε-caprolactone) (PEG-b-PCL) copolymer micelles and their drug-loaded counterparts, as well as the effect of the physiochemical properties of different drugs (phloretin and gossypol). The critical aggregation concentration (CAC) of the copolymers decreased with increasing weight fraction of the PCL block (fPCL), plateauing at ~1 mg/L when the fPCL was >0.45. The blank (empty) and drug-loaded micelles were lyophilized/reconstituted in the absence and presence of β-CD (9% w/w) and analyzed via dynamic light scattering (DLS) and synchrotron small-angle X-ray scattering (SAXS) to assess for changes in aggregate size (hydrodynamic diameter, Dh) and morphology, respectively. Regardless of the PEG-b-PCL copolymer or the use of β-CD, the blank micelles displayed poor redispersibility (<10% relative to the initial concentration), while the fraction that redispersed displayed similar Dh to the as-prepared micelles, increasing in Dh as the fPCL of the PEG-b-PCL copolymer increased. While most blank micelles displayed discrete morphologies, the addition of β-CD or lyophilization/reconstitution generally resulted in the formation of poorly defined aggregates. Similar results were also obtained for drug-loaded micelles, with the exception of several that retained their primary morphology following lyophilization/reconstitution, although no obvious trends were noted between the microstructure of the copolymers or the physicochemical properties of the drugs and their successful redispersion. Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) licence
- ItemLipidic drug delivery systems are responsive to the human microbiome(Elsevier, 2025-01) Caukwell, J; Assenza, S; Hassan, KA; Neilan, BA; Clulow, AJ; Manni, LS; Fong, WKIn vitro and in vivo tests for therapeutic agents are typically conducted in sterile environments, but many target areas for drug delivery are home to thousands of microbial species. Here, we examine the behaviour of lipidic nanomaterials after exposure to representative strains of four bacterial species found in the gastrointestinal tract and skin. Small angle X-ray scattering measurements show that the nanostructure of monoolein cubic and inverse hexagonal phases are transformed, respectively, into inverse hexagonal and inverse micellar cubic phases upon exposure to a strain of live Staphylococcus aureus often present on skin and mucosa. Further investigation demonstrates that enzymatic hydrolysis and cell membrane lipid transfer are both likely responsible for this effect. The structural responses to S. aureus are rapid and significantly reduce the rate of drug release from monoolein-based nanomaterials. These findings are the first to demonstrate how a key species in the live human microbiome can trigger changes in the structure and drug release properties of lipidic nanomaterials. The effect appears to be strain specific, varies from patient to patient and body region to body region, and is anticipated to affect the bioapplication of monoglyceride-based formulations. © 2024 The Author(s). Published by Elsevier Inc - Open Access CC BY 4.0
- ItemRealtime structural characterisation of thin film OLED stacks during thermally induced diffusion - the importance of glass transitions(International Conference on Neutron Scattering, 2017-07-12) Nelson, A; McEwan, JA; Clulow, AJ; Shaw, PE; Darwish, TA; Yepuri, NR; Burn, PL; Gentle, IROrganic Light Emitting Diode (OLED) devices are ubiquitous in the displays of many modern electronic devices, including televisions and mobile phones. High efficiency OLEDs are typically made as a sequentially deposited multilayer, with different organic semiconductor layers being required for hole/electron injection/transport, as well as light emission. The operational lifetime, efficiency and fidelity of these OLEDs depends on the structural stability of this multilayer stack, and understanding the factors that affect this stability are crucial in developing new devices. We have systematically characterised the kinetics of structural evolution in these systems as they experience thermally induced diffusion. These leading edge experiments are performed on the Platypus neutron reflectometer, which has been pioneering event mode acquisition techniques to capture quickly changing reflection signals as the multilayers inter-diffuse. Selective deuteration of these semiconductor materials is also critical in providing neutron contrast between each of the layers, without which the experiment could not be carried out. Our investigations reveal the importance of glass transition temperatures on the stability of these OLED systems and provide clear guidelines for material choices when designing new devices. Indeed, with knowledge of each of the T \'s one can predict the way in which diffusion occurs. For example, use of a high Tg emissive layer does not necessarily prevent diffusion from taking place.
- ItemStructures of biliary micelles during solubilisation of lipids mimicking the digestion products of human and bovine milk(Australian Nuclear Science and Technology Organisation, 2021-11-24) Clulow, AJMilk is our sole source of nutrition for the first six months of life and milk lipids carry fat-soluble nutrients through the gut as well as providing most of the energy we consume with milk. The digestion and absorption of lipids, predominantly triglycerides, and entrained nutrients is therefore important for survival and growth. Milk triglycerides are regarded amongst the most chemically complex mixtures, their composition is species-dependent and determines the mixture of fatty acids and monoglycerides that form during their digestion. Most lipid digestion takes place in the small intestines where bile salts mixed with phospholipids in the intestinal fluids form a colloidal sink into which the poorly-soluble digestion products can partition and be absorbed at the intestinal walls. This work describes attempts to simulate how the structures of biliary micelles change when they absorb milk digestion products under intestinal conditions. Mixtures of fatty acids and monoglycerides were prepared to mimic the digestion products of human and bovine milk. The chemical complexity of the mixtures was varied by including between four and eight different lipid chain types in the digestion product mixtures. The effect of pH on micelle structure was also studied within the range of pH 6.4-7.7, consistent with the increase in pH along the intestinal tract. The structural differences when these complex lipid mixtures were solubilised by bile salt/phospholipid micelles were identified using the SAXS/WAXS beamline at the ANSTO Australian Synchrotron. The lipid composition was found to be a primary driver of micelle shape and size, with pH having a secondary affect in reducing aggregate formation at higher pH. © 2021 The Authors
- ItemTime-resolved neutron reflectometry and photovoltaic device studies on sequentially deposited PCDTBT-fullerenel layers(ACS Publications, 2014-09) Clulow, AJ; Tao, C; Lee, KH; Velusamy, M; McEwan, JA; Shaw, PE; Yamada, NL; James, M; Burn, PL; Gentle, IR; Meredith, PWe have used steady-state and time-resolved neutron reflectometry to study the diffusion of fullerene derivatives into the narrow optical gap polymer poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) to explore the sequential processing of the donor and acceptor for the preparation of efficient organic solar cells. It was found that when [6,6]-phenyl-C61-butyric-acid-methyl-ester (60-PCBM) was deposited onto a thin film of PCDTBT from dichloromethane (DCM), a three-layer structure was formed that was stable below the glass-transition temperature of the polymer. When good solvents for the polymer were used in conjunction with DCM, both 60-PCBM and [6,6]-phenyl-C71-butyric-acid-methyl-ester (70-PCBM) were seen to form films that had a thick fullerene layer containing little polymer and a PCDTBT-rich layer near the interface with the substrate. Devices composed of films prepared by sequential deposition of the polymer and fullerene had efficiencies of up to 5.3%, with those based on 60-PCBM close to optimized bulk heterojunction (BHJ) cells processed in the conventional manner. Sequential deposition of pure components to form the active layer is attractive for large-area device fabrication, and the results demonstrate that this processing method can give efficient solar cells. © 2014, American Chemical Society.