In biochemical environments, amphiphilic molecules form bilayer vesicles that can stabilize polar molecules in their interiors while encapsulating nonpolar guests inside the hydrophobic walls. Radowski et al. sought to mimic this universal carrier ability in a synthetic molecular assembly by fabricating a spherical multishelled structure from three inexpensive commercially available building blocks. For the core, they used hyperbranched poly(ethylene imine) (PEI), which was appended to alkyl diacid segments that in turn were capped by monomethyl poly(ethylene glycol). The chain lengths of all three components were varied to optimize transport properties for guests of widely ranging polarity in water, ethanol, chloroform, and toluene. Uptake of the guest molecules (which included an array of drugs, vitamins, and dyes) was substantially enhanced by using a large PEI core and long (C18) alkyl diacid. Dynamic light-scattering measurements revealed that the macromolecules form aggregates that enhance their transport capabilities. The aggregates, which expanded with linear guests but contracted with globular ones, were highly robust, proving stable to filtration and chromatography and persisting in solution for more than a year. — MSL
Angew. Chem. Int. Ed. 46, 1265 (2007).