Controlling the Release from Enzyme-Responsive Microcapsules with a Smart Natural Shell.

We design a natural and simple core-shell-structured microcapsule, which releases its cargo only when exposed to lipase. The cargo is entrapped inside a gel matrix, which is surrounded by a double-layer shell containing an inner solid lipid layer and an outer polymer layer. This outer polymer layer can be designed according to the intended biological system and is responsible for protecting the microcapsule architecture and transporting the cargo to the desired site of action. The lipid layer contains natural ester bonds, which are digested by lipase, controlling the release of cargo from the microcapsule core. To demonstrate the feasibility of this approach, our model system includes a colorant bixin entrapped inside a κ-carrageenan gel matrix. This core is surrounded by an inner beeswax-palmitic acid layer and an outer casein-poloxamer 338 layer. These fabricated microcapsules are then applied into Cheddar cheese, where they selectively color the cheese matrix.