Converging layer-by-layer polyelectrolyte microcapsule and cubic lyotropic liquid crystalline nanoparticle approaches for molecular encapsulation

Abstract

Microcapsules created by the layer-by-layer (LbL) polyelectrolyte adsorption technique have been sub-compartmentalised by embedding cubic mesophase lipid nanoparticles (cubosomes™) into the capsule shell wall. Monoolein and phytantriol cubosomes™ containing fluorescent lipid and/or positively charged surfactant were first analysed for stability viadynamic light scattering, microelectrophoresis, and small angle X-ray scattering techniques. Once nanoparticle stability was confirmed, cubosomes™ were embedded within a multilayer assembly of oppositely charged polyelectrolytes [poly(allylamine hydrochloride) and poly(styrene sulfonate)] on planar silica substrates. Deposition of each layer was monitored using a quartz crystal microbalance with dissipation monitoring. These findings were then correlated to the growth of polyelectrolyte films incorporating cubosomes™ onto silica microparticles, where ζ-potential measurements were used to monitor the deposition of each subsequent layer. Small angle X-ray scattering experiments provided verification that cubosomes™ remained structurally intact when embedded within the polyelectrolyte matrix. Upon removal of the silica core, stable microcapsules containing one layer of embedded cubic nanoparticles were obtained. A diversity of molecular encapsulation matrices is offered through the capsule core, polyelectrolyte layers, and the embedded cubosomes™ of these sub-compartmentalised, nanostructured microcapsules.