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Seminario
"Multifuctional nanoengineered polymer microcapsules"

Relatore: Gleb Sukhorukov- Senior Scientist, Max Planck Institute of Colloid and Interfaces, 14424, Potsdam/Golm, Germany

Aula Newton
24 Febbraio 2003 ore 16.30

Abstract
Multifuctional nanoengineered polymer microcapsules Gleb B. Sukhorukov Max Planck Institute of Colloid and Interfaces, 14424, Potsdam/Golm, Germany A novel approach to fabricate micro- and nanocapsules is described. The method consists in layer-by-layer adsorption of oppositely charged macromolecules onto colloidal particles. Different templates with size ranged form 50 nm to tens of microns, such as organic and inorganic colloid particles, protein aggregates, emulsion droplets, biological cells and drug nanocrystals can be coated by multilayer film. Various materials have been used as layer constituents to fabricate the shell. The possibility to use various materials allows proper design of shell to adjust required stability biocompatibility and affinity properties of the capsules. Some colloidal templates can be decomposed at conditions where the polymer shell is stable, what leads to the formation of hollow capsules. The permeability through the capsule wall and release of the encapsulated materials depend on the shell wall thickness and composition and can be regulated afterwards by pH, ionic strength or solvent exchange. Several approaches on macromolecule encapsulation into these capsules are developed. This possibility of switching permeability provides a convenient and efficient tool to control the uptake and release of polymers, biopolymers and nanoparticles. The presence of polyelectrolyte only on one side of the capsule wall leads to establish pH-difference across the capsule wall. It has been utilised for synthesis of iron oxide and other magnetide nanoparticle or precipitation of dyes with pH-dependent solubility in capsule interior. Silver nanoparticles can be synthesised exclusively in capsule interior then filled with redoxive polymers. Small molecules (dyes, drugs) can precipitate into restricted volume of capsule with determined size and shell composition. These polyelectrolyte capsules are supposed to be used as carriers for biological species, for the controlled release and targeting of drugs and as microcontainers to perform chemical reactions in restricted volumes.