Anisotropic Micro- and Nano-Capsules

by | Nov 29, 2010

Precise reproduction of inorganic template shape to create hollow cubic and tetrahedral polymeric capsules with excellent pH, shape, and mechanical stability after core removal

Hollow synthetic structures are of great interest for storage and release applications and synthetic cell-like structures. In recent years layer-by-layer self-assembly has proved to be the method of choice to construct spherical microcapsules. However, anisotropic nanocapsules are scarcely reported, eventhough they play an important role in nature, i.e., cell-nanoparticle interaction.

Vladimir V. Tsukruk et al. presents in their recent publication in Macromolecular Rapid Communications the synthesis of aniotropic nanocapsules, which may serve as building blocks for assembly into complex supra-structures with unique properties unachievable through conventional colloids. By layer-by-layer self-assembly the cubic and tetrahedral shapes of the templates were perfectly replicated and hollow capsules with well-defined edges were fabricated. These particles with characteristic dimensions of 1–3mm and 150–500nm composed of 10nm thick polymer shells are stable at physiological pH and retain their integrity at various pH values. In contrast to cubic structures, the construction of tetrahedral structures the additional stress at the edges and corners presents a new challenge. By combining computer modeling and experiments under varying osmotic pressure the authors conclude that the sharp edges and vertices act as a reinforcing frame for the microcapsules.