title: Na+and solute diffusion in aqueous channels of Myverol bicontinuous cubic phase: PGSE NMR and computer modelling.
abstract: The apparent diffusion coefficients of23Na+ions and the solute 2-fluoroethylamine present in the aqueous domain of a Myverol/water bulk bicontinuous cubic phase (BCP) were measured using pulsed field-gradient spin echo (PGSE) NMR spectroscopy. The measured values were dependent on the diffusion time interval, which is a characteristic of restricted diffusion. The translational motion of23Na+and water in the aqueous channels of a cubic phase were simulated using a Monte-Carlo random walk algorithm, and the simulation results were compared with those from real PGSE NMR experiments. The simulations indicated that diffusion of23Na+ions and water would appear to be restricted even on the shortest timescales available to PGSE NMR experiments. The micro-viscosity of the aqueous domain of the BCPs was estimated from the longitudinal relaxation times of23Na+and 2-fluoroethylamine; this was three times higher than in free solution and suggests one of (but not the only) likely impediments to the release of hydrophilic drugs from stabilised aqueous dispersions of BCPs (cubosomes) when they are used therapeutically in vivo. Monte Carlo simulations of diffusive efflux from cubosomes suggest that the principal impediment to drug release is presented by a surfactant or lipid barrier at the cubosome surface, which separates the BCP aqueous channels from the bulk solution. The dynamics inferred from these studies informs quantitative predictions of drug delivery from cubosomes. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Neurosurgery Unit, Department of Clinical Neurosciences, University of Cambridge, United Kingdom.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Larkin
authors.affiliation: Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales, Australia.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Garvey
authors.affiliation: School of Molecular Bioscience, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Shishmarev
authors.affiliation: School of Molecular Bioscience, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Philip W
authors.initials: PW
authors.lastname: Kuchel
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology (QUT), Brisbane, Queensland, Australia.
authors.forename: Konstantin I
authors.initials: KI
authors.lastname: Momot
keywords: 19F NMR; 23Na NMR; Monte-Carlo random walk; cubosome; diffusive efflux; gyroid surface