Angew. Chem. Int. Ed. http://doi.org/fz9t8r (2012)

Credit: © 2012 WILEY

The in vivo behaviour of nanoparticles is known to be dependent on many physical properties including size, shape and charge. Less is understood, however, about the relationship between biological properties and the spatial arrangement of charge on the nanoparticle surface. Now, Han et al. synthesize zwitterionic quantum dots with varying charge distributions and analyse their in vitro and in vivo behaviour. The quantum dots are coated with polymeric ligands containing imidazole units, which bind to the quantum dots in a more chemically stable manner than the commonly used thiol binding group, and either sulphobetaine or carboxybetaine groups. These zwitterionic groups have different binding affinities for the quantum dot surface and hence, result in different charge distributions. Han et al. observe significant nonspecific accumulation of the functionalized quantum dots in the vessels of live mice if positive charges are exposed on the surface but minimal nonspecific accumulation when negative charges are prominent on the surface. This indicates the importance of masking positive charges on the surface of nanomaterials to be used in vivo.