Preparation and characterization of pH-sensitive AB4-type block copolymers with self-assembly
CAO Dan, LUO Yanling*, HU Xijie, XU Feng， DANG Peipei
(School of Chemistry and Chemical Engineering, Shaanxi Normal University,Xi′an 710119, Shaanxi, China)
Abstract:
AB4-type pH-sensitive amphiphilic block copolymers,consisted of pH-sensitive polymethacrylic acid and polylactic acid segments were synthesized in three steps.Firstly, Chloro-polyactic acid (Cl2-PLA-Cl2) was prepared by esterification of HO-PLA-OH and CHCl2COCl. Then, poly(t-butyl methacrylate)-block-polylactic acid-block-poly(t-butyl methacrylate) (PtBMA2-b-PLA-b-PtBMA2) was synthesized via atom transfer radical polymerization. After hydrolysis, polymethacrylic acid-block-polylactic acid-block-polymethacrylic acid (PMAA2-b-PLA-b-PMAA2) was obtained. The copolymers could be spontaneously assembled into spherical core-shell micelles with critical micelle concentration (CMC) of about 19.7~32.5 mg/L and the hydrodynamic diameters below 200 nm. The copolymer micelles exhibited pH sensitivity，and paclitaxel had faster release rate in PBS solution at pH 5.6~7.4 than in PBS at pH 1.4.The copolymers may be used as water-insoluble drug targeting release carriers for intestine cancers.
KeyWords:
biomaterials; micelles; chemical synthesis; drug release
