Multi-Stimuli Responsive\nSequence Defined Multi-Arm\nStar Diblock Copolymers for Controlled Drug Release

Abstract

Star-shaped polymeric\nmaterials provide very high efficiency toward\nvarious engineering and biomedical applications. Due to the absence\nof straightforward and versatile synthetic protocols, the synthesis\nof sequence-defined star-shaped (co)polymers has remained a major\nchallenge. Here, a facile approach is developed that allows synthesis\nof a series of unprecedented discrete, multifunctional four-, six-,\nand eight-arm star-shaped complex macromolecular architectures based\non a well-defined triple (thermo/pH/light)-stimuli-responsive poly(<i>N</i>-isopropylacrylamide)-<i>block</i>-poly(methacrylic\nacid)-umbelliferone (PNIPAM-<i>b</i>-PMAA)_<i>n</i>-UMB diblock copolymer, based on temperature responsive PNIPAM\nsegment, pH-responsive PMAA segment, and photoresponsive UMB end groups.\nThus, developed star-shaped copolymers self-assemble in water to form\nspherical nanoaggregates of diameter 90 ± 20 nm, as measured\nby FESEM. The star-shaped copolymer’s response to external\nstimuli has been assessed against changes in temperature, pH, and\nlight irradiation. The star-shaped copolymer was employed as a nanocarrier\nfor pH responsive release of an anticancer drug, doxorubicin. This\nstudy opens up new avenues for efficient star-shaped macromolecular\narchitecture construction for engineering and biomedical applications.