Hollow nanometer-sized containers are of increasing interest in nanotechnology, since they can protect proteins, enzymes or drugs from hostile surroundings and provide an optimal microenvironment. Here we report on functionalized nanocapsules as intracellular reporters providing a new tool in cell biology. Cell active molecules, hormones, enzymes or reporter molecules may be hidden from the outside, protected against chemical and biological degradation, targeted to specific compartments inside a cell and released in a controlled manner. For example we loaded capsules with antigenic peptides and inject the capsule with electroporation. We describe here the laser-triggered release of peptides into the interior of a cell which is followed by their binding to MHC class I molecules, and the subsequent movement of the peptide-class I complex to the plasma membrane.

In a separate project magnetic fluorescent liposomes were prepared by hydration of dried film of Egg-PC and Rhodamine-B labeled fluorescent lipids with a magnetic fluid (8nm average diameter iron citrated nanoparticles in buffer solution). The iron oxide nanoparticles were prepared by co-precipitation of a mixture of iron chloride salts. Citrate ions were adsorbed at the surface to provide a colloidal stability between pH 4 to pH 10. To separate encapsulated nanoparticles in the liposomes from the free, the suspension was passed through a Sepharose 4B column. After separation the magnetoliposomes were concentrated using a magnet. In a further series we prepared hydrophobic superparamagnetic nanoparticles and entrapped then in the liposomal bilayer. This technique bypasses the step of gel filtration. Further, these magnetoliposomes are coated with alternating polymer polyelectrolyte layers, resulting in magnetoliposome capsules. These capsules are introduced into CHO or Vero cells by either electropermeabilization or microinjection.

Sukhorukov GB, Rogach AL, Garstka M, Springer S, Parak WJ, Munoz-Javier A, Kreft O, Skirtach A, Susha AS, Ramaye Y, Palankar R, Winterhalter M. Multifunctionalized Polymer Microcapsules: Novel Tools for Biological and Pharmacological Applications. Small 3 (2007) 944-55.