NSEF Forum Award Presentation: Nanocrystal-Liposome Complexes

Inorganic nanocrystals are being explored for a variety of uses in biology and medicine, ranging from imaging contrast agents to active therapeutic agents.  Synthetic methods now exist for a wide variety of nanocrystals, ranging from semiconductors to magnetic oxides to metals, providing a wide range of new nanoscopic probes for integration with biological macromolecules.  Most of these synthetic methods, however, employ organic solvents that yield hydrophobic ligand-stabilized nanocrystals.  Particles that do not disperse in water are obviously not directly compatible with biological systems.  To render the nanocrystal surfaces hydrophilic, early efforts focused on exchanging the hydrophobic ligands with hydrophilic ligands.  This process tends to degrade the quality of the materials.  A more general and successful approach has been the addition of various surfactants, like lipids and amphiphilic polymer.  But these molecules may be weakly bound and desorb.  The biocompatibility of many of the coating molecules that have been used is also not known or they have been found to be toxic.  Another approach is to use liposomes as a host scaffold for hydrophobic nanocrystals.  Various liposomes are already approved for medical use and can be effective in some therapeutic applications like cancer treatment.  We have been studying how hydrophobic sterically-stabilized nanocrystals interact with liposomes.  In some cases, the nanocrystals will embed into the hydrophobic core of the lipid membrane without disrupting the integrity of the liposomes.  In other cases, the nanocrystals disrupt liposome formation.  This presentation will cover our latest findings and understanding of how hydrophobic nanocrystals interact with lipids and liposomes.