Browsing by Author "Hawley, A"

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    External manipulation of nanostructure in photoresponsive lipid depot matrix to control and predict drug release in vivo
    (Elsevier B.V., 2016-04-28) Fong, WK; Hanley, TL; Thierry, B; Hawley, A; Boyd, BJ; Landersdorfer, CB
    On-demand drug delivery systems are highly promising to control the time-course of drug release and ultimately optimize drug concentration time profiles in patients. Lipid based lyotropic liquid crystalline mesophases have demonstrated exceptional responsiveness to external stimuli such as heat, pH and light. Our objective was to quantitatively characterize the time-course of light activated drug release from near infrared (NIR) activated photothermal systems using ex vivo and in vivo studies. Photoresponsive hybrid gold nanorod-liquid crystalline matrices were prepared and loaded into custom-made implants which were inserted into subcutaneous tissues in rats. Time resolved SAXS studies showed the abdomen to be the best site of implantation to achieve in vivo activation of the subcutaneous dose from by the NIR laser. External control of drug release was achieved via NIR laser light and plasma concentrations of the model drug were determined over time. Laser activation achieved a phase change of the photoresponsive formulations and thereby a considerable change in the rate of drug release. Population pharmacokinetic modeling of all results simultaneously revealed a two stage release process unique to these liquid crystalline matrices. The developed structural model was able to successfully describe also the results of our previous study in 2009 where a change in temperature was utilized to trigger subcutaneous drug release. Thus, modeling of the data proved to be a valuable analytical tool which provided a quantitative understanding of the time-course of drug release in vivo and will be essential in the development of these matrices as on-demand release systems. © 2016, Elsevier B.V.
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    Impact 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, BJ
    Human 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
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    The mechanical performance of carbon fibres-addressing the role of microstructure
    (Society for the Advancement of Material and Process Engineering, 2019-05-20) Lynch, P; Creighton, C; Fox, D; Santiago, PM; Hawley, A; Mudie, ST
    Copyright 2019. Used by the Society of the Advancement of Material and Process Engineering with permission. A new SAXS-WAXS method has been developed at the Australian synchrotron for the structural analysis of carbon fibres. The new technique, referred to as serial SAXS-WAXS fibre scattering is used to map the microstructural properties of single carbon fibres, ranging in diameter from 5 to 8 µm. Based on an automated scanning protocol, a single carbon fibre is mounted in vacuum and aligned relative to the incident X-ray beam. After (automated) alignment points on each monofilament are acquired. In the forward scattering direction both the SAXS and WAXS signal are recorded as a single image to ensure that the fibre scattering cross-section is known precisely. Under these conditions both the size and alignment of the microstructural features from fibre-to-fibre are quantified. Importantly, the graphitic alignment, spacing and apparent crystallite size can be directly related to the macroscopic fibre modulus. In addition, quantitative analysis of the SAXS scattering signal from pores trapped within the fibre provides an indication of macroscopic strength. The utility of these techniques are demonstrated for carbon fibres prepared on the Carbon Nexus single tow line at 3 different carbonization tensions. © 2019 The Authors.