Scientific objectives of the research group of Wolfgang Parak
The biophotonics group of the University Hamburg focuses on the investigation of new nano- and micro-systems and their applications in a wide variety of fields such as medicine, biology and electronics devices.
Our research activities are structured in three branches:
- synthesis of colloidal nanoparticles
- surface chemistry and bioconjugation of colloidal nanoparticles
- application of colloidal nanoparticles in life science
Synthesis of colloidal nanoparticles
We presently synthesize a broad spectrum of nanoparticles from different materials, such as CdSe, CdSe/ZnS, CdS, CdTe, Fe2O3, CoPt3, FePt, Au. Particles are synthesized in hot organic surfactants and are therefore hydrophobic, they have a high crystalinity and a narrow size distribution. Based on the different materials the particles can have different properties such as being fluorescent, magnetic, and photo-heatable. Latest achievements have allowed for the synthesis of hybrid materials that are as well magnetic as fluorescent.
Surface chemistry and bioconjugation of colloidal nanoparticles
We have developed a very general protocol which allows us to transfer hydrophobic colloidal nanoparticles into aqueous solution. The method is based on embedding the hydrophobic particles in amphiphilic polymers. In this way we can make particles with different functionality (due to the nanoparticle material), but with identical surface chemistry. Variations of the polymer also allow for high flexibility. We can add for example specific ligands or other functional groups to the polymer, which are then present of the surface of the particles. Our specialty is to synthesize nanoparticles with exactly one, two, or three molecules bound per nanoparticle.
Application of colloidal nanoparticles in life science
On a general level we investigate the interaction of nanoparticles with cells, in particular their uptake. By embedding nanoparticles of several materials in the shells of micrometer sized polyelectrolyte capsules we can combine the properties of different materials in one carrier system. Magnetic nanoparticles in the shells of the capsules allow for directing them with magnetic field gradients. Fluorescent nanoparticles in the shells of the capsules allow for visualizing them. Photo-heatable nanoparticles in the shells of the capsules allow for heat generation in the shell by optical excitation, which causes the shell to break and a cargo from the capsule cavity can be released. These three properties are combined in one carrier system which we are starting to use for local and remotely controlled delivery. The same capsules can also be loaded with analyte sensitive fluorophores and can be used for the detection of local analyte concentrations inside and outside cells.