Ulrike Alexiev

Title: Visualization and characterization of nanocarriers for dermal drug delivery using single molecule methods

Ulrike Alexiev

Freie Universitat Berlin, Germany


1983-1988 Study of Biophysics at Humboldt University Berlin
1990-1994 PhD work at Freie Universität Berlin and MIT, USA
1995-2002 Post doc and Habilitation
2003- present Group leader at Freie Universität Berlin (Field: Molecular Biophysics and Nanomedicine)


The use of modern single molecule TIRF microscopy enables the characterization of single drug molecules in terms of diffusivity in the skin and localization within the nanocarrier. I present two examples: i) diffusivity and localization of molecules within the stratum corneum of the skin, and ii) localization of cargo within nanostructured lipid carriers.

The skin represents an effective physical and biochemical barrier, thus treatment of skin disorders by topical therapy, i.e., topical application of active molecules on the skin surface, is challenging. Penetration of topically applied drug molecules is often observed to be limited by the size of the respective drug. However, the molecular mechanisms which govern the penetration of molecules through the outermost layer of the skin are still largely unknown. Single molecule based methods allow to understand the pathways and molecular interaction. 

Nanostructured lipid carriers (NLCs) and their predecessors, the solid lipid nanoparticles (SLN), are nanoparticles made from lipids and were developed to increase the bioavailability of lipophilic actives and are also used for skin treatments. Investigation of these nanostructures with sizes below the diffraction limit of visible light is quite challenging. A novel tool based on single-molecule microscopy is now available that allows for the precise determination of drug distribution and the characterization of lipid nanostructures, information that is paramount for optimizing lipid nanoparticle formulations.

Takeaway Notes

  • Introduction to advanced single molecule and advanced fluorescence techniques to be used in the field of drug delivery
  • Localization of drug molecules with nm-precision and high sensitivity within tissue (example stratum corneum)
  • Application of the technique to the characterization of lipid nanoncarrier (as an example) in terms of drug distribution, nanocarrier shape and internal morphology, and drug release and how this helps to develop tailor-made nanocarriers.