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Na + and solute diffusion in aqueous channels of Myverol bicontinuous cubic phase: PGSE NMR and computer modelling
Author(s) -
Larkin Timothy J.,
Garvey Christopher J.,
Shishmarev Dmitry,
Kuchel Philip W.,
Momot Konstantin I.
Publication year - 2017
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4432
Subject(s) - chemistry , aqueous solution , diffusion , pulsed field gradient , relaxation (psychology) , aqueous two phase system , phase (matter) , nuclear magnetic resonance spectroscopy , monte carlo method , analytical chemistry (journal) , chemical physics , thermodynamics , chromatography , molecule , organic chemistry , physics , psychology , social psychology , statistics , mathematics
The apparent diffusion coefficients of 23 Na + 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 of 23 Na + 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 of 23 Na + 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 of 23 Na + 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.