Supramolecular amphiphilic multiarm hyperbranched copolymer: synthesis, self-assembly and drug delivery applications

Novel supramolecular amphiphilic multiarm hyperbranched copolymers were successfully constructed through the molecular recognition of nucleobases. First, adenine-terminated H40-star-poly(ε-caprolactone)-adenine (H40-star-PCL-A) and uracil-terminated poly(ethylene glycol) (PEG-U) were successfully prepared. Due to the molecular recognition between A and U moieties, supramolecular multiarm hyperbranched copolymers were obtained by simply mixing the hydrophobic H40-star-PCL-A core and hydrophilic PEG-U shell. They not only had similar properties to conventional covalent-linked multiarm hyperbranched copolymers, but also possessed a dynamic and tunable nature. These supramolecular hyperbranched copolymers were found to self-assemble into pH-responsive micelles with low critical micelle concentration (CMC) because of non-covalent connection and hyperbranched architecture. The size of the self-assembled micelles could be easily tailored by changing the ratio of hydrophobic H40-star-PCL-A core and hydrophilic PEG-U arm. Moreover, encapsulation and controlled drug release were demonstrated with the chemotherapeutic drug doxorubicin (DOX). These supramolecular hyperbranched copolymer systems represent an evolution over conventional stimuli-responsive covalent-bonded hyperbranched copolymer systems and display a significant reduction in the viability of HeLa cells upon triggered release of DOX from the supramolecular micelles.