Facile fabrication of nanocomposite microcapsules by combining layer-by-layer self-assembly and Pickering emulsion templating
Nanocomposite polysaccharide microcapsules composed of biocompatible polyelectrolyte complexes are prepared via electrostatic layer-by-layer (LbL) self-assembly based on a Pickering emulsion template method. Polyethyleneimine (PEI)–Laponite based Pickering emulsions are obtained regardless of the polarity and viscosity of the oils, at a PEI/Laponite mass ratio of 0.50 and a Laponite concentration of 0.25 wt%, and these emulsions show good long-term stability for more than two months. Four-bilayer sodium alginate–chitosan microcapsules, with dimensions of about 43.9 μm and wall thickness of 55 nm, are prepared by alternate adsorption of negatively charged sodium alginate and positively charged chitosan on Pickering emulsions. Hollow microcapsules are obtained after core removal using a mild method of washing with excess 2-propanol. Ibuprofen (IBU), as a model drug, is loaded into the hollow microcapsules, and the release rate of IBU from the microcapsules at pH 7.4 is obviously faster than the release rate at pH 2.0. The greater the number of polyelectrolyte layers of the IBU-loaded microcapsules, the more difficult the IBU release. Consequently, nanocomposite microcapsules composed of natural polysaccharides fabricated by a Pickering emulsion templated LbL assembly method offer great potential applications in the food and medical industries.