Multi-Stimuli Responsive Sequence Defined Multi-Arm Star Diblock Copolymers for Controlled Drug Release

Star-shaped polymericmaterials provide very high efficiency towardvarious engineering and biomedical applications. Due to the absenceof straightforward and versatile synthetic protocols, the synthesisof sequence-defined star-shaped (co)polymers has remained a majorchallenge. Here, a facile approach is developed that allows synthesisof a series of unprecedented discrete, multifunctional four-, six-,and eight-arm star-shaped complex macromolecular architectures basedon a well-defined triple (thermo/pH/light)-stimuli-responsive poly(N-isopropylacrylamide)-block-poly(methacrylicacid)-umbelliferone (PNIPAM-b-PMAA)( n )-UMB diblock copolymer, based on temperature responsive PNIPAMsegment, pH-responsive PMAA segment, and photoresponsive UMB end groups.Thus, developed star-shaped copolymers self-assemble in water to formspherical nanoaggregates of diameter 90 & PLUSMN; 20 nm, as measuredby FESEM. The star-shaped copolymer's response to externalstimuli has been assessed against changes in temperature, pH, andlight irradiation. The star-shaped copolymer was employed as a nanocarrierfor pH responsive release of an anticancer drug, doxorubicin. Thisstudy opens up new avenues for efficient star-shaped macromoleculararchitecture construction for engineering and biomedical applications.