Synthesis of Pentablock and Multibranched Copolymers Bearing Poly(ethylene glycol), Hyperbranched Polyglycidol, and Poly(L-lactide) with Biocompatibility for Controlled Drug Release

A series of multibranched pentablock copolymer (mBr5BlC), poly(L-lactide)-b-HBP-b-poly(ethylene glycol)-b-HBP-b-poly(L-lactide) (HBP = hyperbranched polyglycidol), has been synthesized by ring-opening multibranching polymerization of glycidol using bifunctional poly(ethylene glycol) [PEG; molecular weight (MW) = 1000] as an initiator, followed by ring-opening polymerization (ROP) of L-lactide in the presence of stannous octoate. The ROP of different amounts of L-lactide on HBP-b-PEG-b-HBP [MW = 2550; polydispersity index (PDI) = 1.08] yielded a series of the targeted mBr5BlCs of the MW range of 4360-15,300 with narrow PDI. All the mBr5BlCs have been well demonstrated to be in possession of good biocompatibility as biomaterials for various applications in biological medicine areas. The mBr5BlCs with tunable MW exhibited promising controllability in self-assembly into spherical micellar structures with an average diameter range of 59-140 nm, which have no acute and intrinsic cytotoxicity against normal cells and provide a convenient strategy for drug loading. The anticancer drug doxorubicin was demonstrated to have a good affinity with the copolymer system, and its controlled release was performed in various pHs. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 2553-2564, 2012