Letter abstract
Nature Materials 5, 724 - 729 (2006)
Published online: 20 August 2006 | doi:10.1038/nmat1716
Subject Category: Polymers
Redox-controlled molecular permeability of composite-wall microcapsules
Yujie Ma1, Wen-Fei Dong2, Mark A. Hempenius1, Helmuth Möhwald2 & G. Julius Vancso1
Many smart materials in bioengineering, nanotechnology and medicine allow the storage and release of encapsulated drugs on demand at a specific location by an external stimulus. Owing to their versatility in material selection, polyelectrolyte multilayers are very promising systems in the development of microencapsulation technologies with permeation control1, 2, 3, 4 governed by variations in the environmental conditions5, 6, 7, 8. Here, organometallic polyelectrolyte multilayer capsules, composed of polyanions and polycations of poly(ferrocenylsilane) (PFS), are introduced. Their preparation involved layer-by-layer self-assembly onto colloidal templates followed by core removal. PFS polyelectrolytes feature redox-active ferrocene units in the main chain. Incorporation of PFS into the capsule walls allowed us to explore the effects of a new stimulus, that is, changing the redox state9, 10, on capsule wall permeability. The permeability of these capsules could be sensitively tuned via chemical oxidation, resulting in a fast capsule expansion accompanied by a drastic permeability increase in response to a very small trigger. The substantial swelling could be suppressed by the application of an additional coating bearing common redox-inert species of poly(styrene sulfonate) (PSS-) and poly(allylamine hydrochloride) (PAH+) on the outer wall of the capsules. Hence, we obtained a unique capsule system with redox-controlled permeability and swellability with a high application potential in materials as well as in bioscience.
- Department of Materials Science and Technology of Polymers, MESA+ Research Institute for Nanotechnology, University of Twente, PO Box 217, NL-7500 AE Enschede, The Netherlands
- Max Planck Institute of Colloids and Interfaces, Golm/Potsdam, D-14476, Germany
Correspondence to: G. Julius Vancso1 e-mail: g.j.vancso@tnw.utwente.nl
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