Tuning polymersome surfaces: functionalization with dendritic groups

The conjugation of dendrons having varying peripheral functionalities to polymer vesicles, commonly referred to as polymersomes, provides an opportunity to significantly alter the polymersome surface chemistry in a single step while leaving intact the block copolymers responsible for assembly. In this work, polymersomes with surface azide groups were prepared from poly(1,2-butadiene)-poly(ethylene oxide) (PBD-PEO) and poly(epsilon-caprolactone)-PEO (PCL-PEO) block copolymers and were functionalized with polyester dendrons having focal point alkyne moieties and peripheral hydroxyls, amines, or guanidines. The release rates of a small molecule rhodamine B and a rhodamine B-labeled protein from naked and functionalized polymersomes were investigated and the presence of dendritic groups was found to have a minimal effect. All of the naked and functionalized polymersomes were found to be nontoxic at all concentrations tested, except for the guanidine functionalized polymersomes which did impart some toxicity at the highest concentrations tested. The cell uptake of the different polymersomes was compared and it was found that the guanidine functionalized polymersomes exhibited increased cell uptake relative to all other materials. Further studies of this phenomenon suggested that the uptake is mediated by endocytosis and possibly direct translocation across the membrane.