Unimolecular micelles based on hyperbranched polycarbohydrate cores

This Review article details the preparation and encapsulation-release properties of novel amphiphilic hyperbranched polymers with a micellar characteristic as a single molecule, which are referred to as unimolecular micelles'' or unimolecular nanocapsules''. Amphiphilic hyperbranched polymers consisting of a hydrophilic hyperbranched polycarbohydrate core and hydrophobic shell possess an ability to encapsulate hydrophilic guest molecules and control the release of the encapsulated guest molecules, e. g., a biodegradable unimolecular reversed micelle consisting of a hyperbranched D-mannan core and a poly(L-lactide) shell, and the pH-sensitive unimolecular reversed micelle consisting of a hyperbranched D-glucan core and L-leucine ethyl ether shell. An amphiphilic hyperbranched polymer consisting of a hyperbranched polythreitol as the hydrophilic core and trityl groups as the hydrophobic shell acts as unimolecular nanocapsule, and shows a high encapsulation ability for guest molecules. Amphiphilic hyperbranched polymer with a hydrophobic core and hydrophilic L-aspartic acid shell possess encapsulation properties for hydrophobic molecules in water. Hence, hyperbranched polymers are found to be good candidates for the dendritic core molecule of a unimolecular micelle or unimolecular nanocapsule.