Self-Destructing "Mothership" Capsules for Timed Release of Encapsulated Contents

We describe a new class of hierarchical containers that are formed via single-step assembly and, at a later time, self-destruct because of their packaged contents. These containers are spherical capsules formed by electrostatic complexation of the anionic biopolymer, gellan gum, with the cationic biopolymer, chitosan. The capsules are termed "motherships" and are engineered to carry a cargo of much smaller containers (e.g., nanoscale liposomes ("babyships")), within their lumen. Additionally, we package an enzyme, chitosanase, in the capsule that is capable of degrading polymeric chitosan into short oligomers. Thereby, we create motherships that self-destruct, liberating their cargo of babyships into the external solution. The time scale for self-destruction can be engineered based on the internal concentration of enzyme. The motherships are stable when stored in a freeze-dried form and can be readily dispersed into water or buffer solutions at a later time, whereupon their "internal clock" for self-destruction is initiated. The above concept could be useful for the triggered release of a variety of payloads including drugs, biological therapeutics, cosmetics, and flavor ingredients.