A Priority Programme of the Deutsche Forschungsgemeinschaft

In any given environment (gas or liquid) nanoparticles will "equilibrate" in shape, size, aggregation and surface composition. Therefore, when NPs enter from the gas phase into a liquid phase or even from an aqueous solvent into biological fluids these properties change. This is due to the changes in tension forces, the reactive environment or other modes of condensed phase interactions including hydrogen bonding, hydrophobic attraction, complexation etc. Moreover, in biological environments NPs may also exchange ligands, cross biological membranes, bind to or enter cells of various types via endocytotic or other yet to be defined processes. In a subsequent series of transcellular or paracellular mechanisms nanoparticles may also be translocated through subsequent layers of cells and sub-cellular structures.

This research field therefore addresses all aspects of the transition of NPs across phase boundaries as well as the interaction with biomolecules, cells and cell constituents, viz.:

  • Phase transfer of NPs from gas to condensed surfaces including rates of accommodation on aqueous and surfactant loaded surfaces.
  • Changes of the interfaces of NPs in body fluids and cells including NP transformations in size, shape, morphology and ligands.
  • Mechanisms and rates of NP/protein interactions as well as cellular uptake.
  • Identification of rate-determining NP parameters for translocation kinetics across membranes such as the air-blood-barrier or the blood-brain-barrier.

Experimental studies will also be corroborated with theoretical approaches including e.g. quantum/classical molecular dynamical simulations of specific surface/protein interactions.

It is anticipated that method development is necessary for studies of the changes of NPs upon `phase transfer` in body fluids and cells. This requires the adoption and modification of surface specific characterisation methods as developed above for in situ and site specific studies of NPs. Likewise, the studies of interactions of NPs with proteins as well as their translocations require the availability of time and space resolved identification and analysis techniques including confocal and/or fluorescence microscopy with nanoscale resolution.

3. The impact of nanoparticles on fundamental biological functions