Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 18: Functionalized Nanoparticles

BP 18.4: Talk

Wednesday, March 28, 2007, 14:45–15:00, H43

Polymer-coated inorganic nanocrystals with a defined number of functional groups — •Ralph Sperling, Marco Zanella, and Wolfgang Parak — Ludwig-Maximilians-Universität München, Center for NanoScience, Amalienstr. 54, 80799 München, Germany

Inorganic hydrophobic nanoparticles of different materials such as Au, CdSe/ZnS, CoPt etc. can be coated with an amphiphilic polymer to yield particles that are stable in aqueous solution.

The carboxylic groups on the surface of the polymer shell serve as anchor points for further chemical functionalization. Ligand molecules with amino groups can be covalently bound to the particles. Poly(ethylene glycol) (PEG) is an inert biocompatible polymer that is known to decrease unspecific binding of particles to surfaces and to increase the colloidal stability at physiological salt concentrations. With bifunctional PEG molecules, the particles can be modified with additional functional groups such as amines, thiols, maleimides etc.

By the increase in size, the binding of the PEG molecules to the particles can be monitored by gel electrophoresis and other techniques. If the molecular weight of the PEG molecule is high enough, conjugates of nanoparticles with one, two, and three PEG molecules per nanoparticle can be separated using gel electrophoresis. In this way the PEG molecules act as spacers that allow the sorting of nanoparticles with a discrete number of functional groups, in order to eliminate uncontrolled inter-particle crosslinking in further experiments.