Pulsed in vitro release and in vivo behavior of exploding microcapsules.

Drug delivery systems which can generate multiple drug pulses after a single injection can be of major importance for e.g. the delivery of vaccines which often require multiple booster injections to generate sufficient immunity. In this paper, we report self-exploding microcapsules which can release their content in a pulsed fashion after a certain incubation time at physiological conditions. The system is based on a biodegradable microgel core surrounded by a bio-polyelectrolyte membrane. When the microgel core degrades, the swelling pressure increases and finally ruptures the membrane leading to release of the encapsulated materials. We show that the explosion time and subsequent release of 50 nm latex nanoparticles (used as a model), can be tailored by varying the cross-link density of the microgels. Further we also address the biocompatibility in vivo after subcutaneous injection of the microcapsules in mice.