Faculty of Physics, University of Marburg, Renthof 7, 35037 Marburg, Germany
With a very general procedure inorganic hydrophobic nanoparticles of different materials can be transferred into aqueous solution by coating them with an amphiphilic polymer that is based on a poly(maleic anhydride) backbone modified with alkylamine sidechains. Functional groups with an amino anchor can be directly introduced in the polymer by reacting them to anhydride groups of the backbone. This offers a very general route to water-soluble nanoparticles of high colloidal stability, with good size distribution, and with a variety of functional groups that are directly embedded in the polymer shell without the need of post-bioconjugation.
Polyelectrolyte microcapsules have been loaded with a pH sensitive, high molecular weight SNARF-1-dextran conjugate. SNARF-1 exhibits a significant pH-dependent emission shift from green to red fluorescence under acidic and basic conditions, respectively. The spectral properties of the dye were found to be largely retained after the encapsulation. Upon ingestion of SNARF-1-filled capsules by breast cancer cells or fibroblasts, the pH change of the local capsule environment during transition from the alkaline cell medium to the acidic endosomal/lysosomal compartments could be observed. By incorporating magnetic and fluorescent colloidal nanoparticles into the capsule-shell a novel type of multiplexed sensor system was developed.