ORCID Profile
0000-0002-2528-8982
Current Organisation
University of South Australia
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Publisher: Elsevier BV
Date: 12-2018
DOI: 10.1016/J.JCIS.2018.08.015
Abstract: Solid-state lipid formulations, whereby liquid lipids are encapsulated in inorganic particle matrices, have attracted significant interest for drug/nutrient delivery in recent years. We hypothesized that the surface chemistry of the inorganic material used to encapsulate lipids impacts the lipase-mediated digestion and partitioning of lipolytic species between the solubilized aqueous and insoluble pellet phases. Medium chain triglycerides were spray dried with silica nanoparticles, montmorillonite or laponite platelets to form inorganic-lipid hybrid particles. In vitro lipolysis studies were conducted under gastric (pH 1.6) and intestinal (pH 7.5) conditions, and the speciation and partitioning of lipolytic products between the aqueous and pellet phases was characterized using solution-state proton nuclear magnetic resonance and fourier transform infrared spectroscopy. Under gastric conditions, greater than 80% of all lipid species remained adsorbed within each lipolysis pellet after 60 min. Approximately 40%, 50-60% and 80-90% of all lipid species were adsorbed from solution by silica-, montmorillonite- and laponite-based particle matrices during intestinal lipolysis. Monoglycerides were preferentially adsorbed by silica, whereas triglycerides and fatty acids were adsorbed by montmorillonite and laponite. Adsorption of lipolytic products from solution is expected to impact significantly on drug/nutrient solubilization and absorption in vivo. To the best of our knowledge, this is the first report characterizing the speciation and phase behavior of lipolytic products released from solid-state lipid formulations during in vitro lipolysis studies.
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.COLSURFB.2019.01.017
Abstract: The interfacial behavior of surfactants present in a natural extract from Quillaja saponaria Molina bark at the air-solution interface is studied by measurements of interfacial tension, interfacial elasticity, and interfacial reflectance FTIR spectroscopy. The active molecule, saponin, is observed directly at the air-solution interface (via reflectance FTIR spectroscopy) above and below the pKa of the molecule, and spectra confirm the altered charge of the interfacial layer at the two solution conditions. For all concentrations of saponin studied, and at pH values below and above pKa (i.e. pH 3 and 7), a reduction in interfacial tension as a function of time is observed, with some differences in early time-scale adsorption and with lower values of quasi-equilibrium interfacial tension for pH 3. The interfacial layer is seen to be elastic, as determined from measurements of hydrostatic expansion, with some variation at the two pH values, and as a function of concentration. In addition to interfacial layer characterisation, the interaction between two air-solution interfaces is probed using bubble collisions with an air-solution interface. This experiment allows for observation of thin film drainage kinetics and determination of the final foam film thickness for the case when one of the interfaces is at equilibrium while the dynamic adsorption layer is being established at the other. This is the first time when the interactions between such interfaces (i.e. only one being at equilibrium) have been studied. This is of particular importance for the formation stage of foams, during which time many of the interfaces are not at equilibrium. When two interfaces interact across a thin liquid film, pH is seen to significantly influence foam film thickness.
Publisher: Springer Science and Business Media LLC
Date: 13-12-2018
DOI: 10.1038/S41598-018-34673-4
Abstract: Soft polymer films, such as polyelectrolyte multilayers (PEMs), are useful coatings in materials science. The properties of PEMs often rely on the degree of hydration, and therefore the study of these films in a hydrated state is critical to allow links to be drawn between their characteristics and performance in a particular application. In this work, we detail the development of a novel soft contact cell for studying hydrated PEMs (poly(sodium 4-styrenesulfonate) oly(allylamine hydrochloride)) using FTIR microspectroscopy. FTIR spectroscopy can interrogate the nature of the polymer film and the hydration water contained therein. In addition to reporting spectra obtained for hydrated films confined at the solid-solid interface, we also report traditional ATR FTIR spectra of the multilayer. The spectra (microspectroscopy and ATR FTIR) reveal that the PEM film build-up proceeds as expected based on the layer-by-layer assembly methodology, with increasing signals from the polymer FTIR peaks with increasing bilayer number. In addition, the spectra obtained using the soft contact cell indicate that the PEM film hydration water has an environment/degree of hydrogen bonding that is affected by the chemistry of the multilayer polymers, based on differences in the spectra obtained for the hydration water within the film compared to that of bulk electrolyte.
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