Biological cell as templates for hollow microcapsules

Microcapsules in the micrometer size range with walls of nanometer thickness are of both scienti®c and technological interest, since they can be employed as micro- and nano-containers. Liposomes represent one example, yet their general use is hampered due to limited stability and a low permeability for polar molecules. Microcapsules formed from polyelectrolytes o er some improvement, since they are permeable to small polar molecules and resistant to chemical and physical in ?uences. Both types of closed ®lms are, however, limited by their spherical shape which precludes producing capsules with anisotropic properties. Biological cells possess a wide variety of shapes and sizes, and, thus, using them as templates would allow the production of capsules with a wide range of morphologies. In the present study, human red blood cells (RBC) as well as Escherichia coli bacteria were used; these cells were ®xed by glutardialdehyde prior to layer-by-layer (LbL) adsorption of polyelectrolytes. The growth of the layers was veri®ed by electrophoresis and ?ow cytometry, with morphology investigated by atomic force and electron microscopy; the dissolution process of the biological template was followed by confocal laser scanning microscopy. The resulting microcapsules are exact copies of the biological template, exhibit elastic properties, and have permeabilities which can be controlled by experimental parameters; this method for micro- capsule fabrication, thus, o ers an important new approach for this area of biotechnology.