Layer-by-layer polyelectrolyte microcapsules with tunable release behaviour and versatile encapsulation ability

Abstract

Layer-by-layer (LbL) polyelectrolyte microcapsules with pre-loaded red blood cells (RBCs) ghosts and calcium carbonate (CaCO3) microparticles as template cores were developed in this project. Taking advantage of the unique features of these templates, LbL polyelectrolyte microcapsules with a simplified preparation process, versatile encapsulation capability and tunable release ability are obtained.

RBCs were loaded with hydrophilic compounds (FITC-dextran or RITC-lysozyme) using hypotonic dialysis loading method. SEM and confocal fluorescent microscope confirmed the loading of compounds into the intact RBCs ghosts. The loaded RBCs ghosts were then coated with different layers of polyelectrolytes. Unlike the traditional solid polymeric templates, the pre-loaded RBCs ghosts can eliminate the core dissolution and substance post-loading steps. The release behaviors become tunable through adjusting the coated polyelectrolyte layer numbers. The release is principally controlled via solutes diffusion through the intact polyelectrolyte membrane.

Porous CaCO3 microparticles were coated with PLGA layer containing hydrophobic compounds via PLGA in situ precipitation technique. The intact PLGA microcapsules were confirmed by confocal fluorescent microscope, AFM, SEM, TGA and ζ-potential studies. The PLGA microcapsules were further coated with multilayer polyelectrolytes to control the drug release behaviors, where dual-drug releasing carriers can also be obtained.