8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P5.130Wed 711:10-14:00Ultrastable superparamagnetic nanoparticle design formembrane assembly and triggered releaseErik Reimhult 11 University of Natural Resources and Life Sciences (BOKU) Vienna, Muthgasse 11,A-1190, Vienna, AustriaApplication of superparamagnetic iron oxide nanoparticles (SPIONs) as biomedical imagingcontrast agents and as actuators in smart materials, e. g. for drug delivery and release, requirethem to retain high stability even in extremely dilute suspensions, high salt and at elevatedtemperatures. These requirements can only be met by steric repulsive stabilization throughirreversibly binding, low molecular weight dispersants of e. g. poly(ethylene glycol) or a similarlyirreversibly bound organic shell which stabilizes the nanoparticle into another matrix material.We have recently demonstrated that we can stabilize SPIONs which fulfil these stability criteriausing self-assembling dispersants with nitrocatechol anchors [1]. This allows us free controlover the dispersant type by simple co-adsorption of dispersants to as-synthesized core Fe 3 O 4particles. Combined with independent control over the Fe3O4 core size in the range 3-15 nma versatile toolbox for assembly of various smart materials and for biomedical applications hasbeen created. This presentation is focussed on recent results demonstrating and characterizingstable liquid interface type assembly of such SPIONs into membranes of stealth liposomes[2]. Encapsulated molecules were released multiple times by application of short bursts ofalternating magnetic fieldsthrough a localized phase change in the membrane without heating ofthe surrounding aqueous environment. The highest efficiency of release and encapsulation wasobtained for irreversibly stabilized SPIONs with diameters ¡6 nm inserted into the lipid membrane.[1] E. Amstad et al. , Nano Lett, 9:4042 (2009).[2] E. Amstad et al. , Nano Lett, asap (2011).130