Scientists at the CAS Institute of Chemistry have been succeeded in fabricating stable hollow capsules by extending covalent layer-by-layer self-assembly (CSA) technique from 2-dimensional to 3-dimensional systems. Hollow capsules at micrometer and nanometer levels could be coaxed into artificial cells, which are used, among other things, for the simulation of bio-chemical reactions in the building blocks of most organisms in nature, for they are more easily manageable than the real cells. In 1998 H. Mohwald and colleagues at Max-Planck-Institute of Colloids and Interfaces synthesized, for the first time in the world, such capsules by employing the layer-by-layer strategy, which has such advantages as finely tuned polymer layer thickness, easily assembled multicomposites. However, until recently, most such studies were done by using a method called electrostatic self-assembly, which is limited to aqueous system and its shell is not stable enough due to the ionic cross-linking nature of the self-as-sembled layer.
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