Influence of pH upon in vitro sustained dye-release from oil-core nanocapsules with multilayer shells

An ideal drug-delivery system should combine both the stimuli-responsiveness and biocompatibility to enhance the drug bioactivity as well as to reduce side effects. In the present work we focused on the influence of pH upon in vitro sustained dye-release from multilayer oil-core nanocapsules. Three types of polyelectrolytes (PEs), two strong synthetic, poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) and one weak biocompatible: poly(l-lysine) hydrobromide, were used for the formation of sustained release, oil-core nanocapsules via layer-by-layer (LbL) self assembly approach. All nanocarriers coated with PSS/PLL or PSS/PDADMAC bilayers were created on the oleic acid nanoemulsion templates stabilized by dicephalic-type surfactant and loaded with hydrophobic, cyanine-type photosensitizer, IR-786. Nanocapsules with different thicknesses of the PE shell and average size around 100 nm, demonstrated good capacity for cyanine IR-786 encapsulation. We determined the sustained release of cyanine dye in different pH-conditions - physiological, acidic and alkaline. The in vitro release profiles were obtained spectrophotometrically and interpreted in terms of diffusion-controlled processes. They proved that pH condition had some influence on the release rate of the dye. It indicates on the necessity of appropriate selection of anionic and cationic polyelectrolytes in the fabrication process of pH-responsive and long sustained release nanocapsules.