Micropackaging via layer-by-layer assembly: microcapsules and microchamber arrays

The micropackaging of chemical compounds in a small and precisely defined quantity, which can be encased, stored, is essential for response to a specific chemical, biological or physical trigger in a controllable manner is one of the premier challenges in the development of delivery systems. In this review, the authors discuss the application of layer-by-layer (LbL) assemblies of macromolecules for micropackaging and controlled release of various types of cargo. The LbL assembly method provides unique opportunities by incorporation of different functional and responsive layer constituents tailored into one entity. Micron and submicron sized capsules made on colloidal templates are used for biomolecule encapsulation and enable time- and site-specific release when triggered by pH, temperature, specific enzymes, mechanic load, light, ultrasound, or magnetic field. In comparison to individual capsules, the authors discuss the recently introduced micropackaging approach involving cargo loading into arrays of microchambers, made by a combination of imprinting technology and LbL assembly. In conclusion, the authors summarise advantages and fabrication obstacles for micropackaging in capsules and microchambers and discuss already existing as well as potential future applications.