A novel pulsed drug-delivery system: polyelectrolyte layer-by-layer coating of chitosan-alginate microgels.

Purpose: The aim of this report was to introduce a novel "core-membrane" microgel drug-delivery device for spontaneously pulsed release without any external trigger. Methods: The microgel core was prepared with alginate and chitosan. The semipermeable membrane outside the microgel was made of polyelectrolytes including polycation poly(allylamine hydrochloride) and sodium polystyrene sulfonate. The drug release of this novel system was governed by the swelling pressure of the core and the rupture of the outer membrane. Results: The size of the core-membrane microgel drug-delivery device was 452.90 +/- 2.71 mu m. The surface charge depended on the layer-by-layer coating of polyelectrolytes, with zeta potential of 38.6 +/- 1.4 mV. The confocal microscope exhibited the layer-by-layer outer membrane and inner core. The in vitro release profile showed that the content release remained low during the first 2.67 hours. After this lag time, the cumulative release increased to 80% in the next 0.95 hours, which suggested a pulsed drug release. The in vivo drug release in mice showed that the outer membrane was ruptured at approximately 3 to 4 hours, as drug was explosively released. Conclusion: These data suggest that the encapsulated substance in the core-membrane microgel delivery device can achieve a massive drug release after outer membrane rupture. This device was an effective system for pulsed drug delivery.