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Jan van Hest: "Bio-inspired compartmentalization strategies"

Wann 15.07.2013
von 11:15 bis 12:00
Wo FRIAS Seminar Room, Albertstr. 19, 79104 Freiburg
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Jan van Hest
Radboud University Nijmegen, The Netherlands


Bio-inspired compartmentalization strategies

In nature many biological processes are compartmentalized to ensure their integrity and efficiency. Inspired by this phenomenon, we have been exploring hybrid capsules based on a combination of proteins and amphiphilic block copolymers to construct bioactive compartments. In this lecture I will present several examples of functionalized polymer vesicles, or polymersomes.
In a first example polymersomes are explored as nanoreactors. Intrinsically porous polymersomes were loaded with different enzymes involved in a cascade reaction. Due to the presence of the polymer shell, the enzymes were protected against proteolytic degradation. This allowed us to apply these nanoreactors in living cells as artificial organelles to scavenge reactive oxygen species. Besides performing multiple enzymatic reactions in one polymersome, we have also investigated the possibility to encapsulate multiple polymersome nanoreactors in a larger polymersome. This polymersome architecture, which mimicks the structural build-up of a eukaryotic cell, was able to perform a three-step cascade, with localized production of the final compound.
A different type of polymersome architecture was obtained by applying crosslinked polymersome nanoreactors. These stabilized structures could now not only be applied in an aqueous environment, but also at the water-organic phase interface as colloidal particles for the stabilization of Pickering emulsions. The high interfacial area in which the enzymes were positioned enabled us to make optimal use of their catalytic activity.
Finally, a different method of compartmentalization was realised using non-permeable polymersomes, composed of polystyrene-poly(ethylene glycol). After self-assembly in a mixture of organic solvent and water, these solvent-swollen polymersomes were dialysed in the presence of platinum nanoparticles. Due to the preferred diffusion of organic solvent out of the capsules, the polymersomes experienced an osmotic pressure difference and became indented, thereby encapsulating Pt nanoparticles in the newly formed nanocavities. After removal of the organic solvent, the PS hydrophobic layer became vitrified, thereby locking in the obtained bowl-shaped polymer assemblies filled with the catalytic Pt nanoparticles. These nanoparticles produced oxygen gas in the presence of the fuel hydrogen peroxide, which propelled the polymersomes and turned them into nano-rockets.