Morphology and in vitro release kinetics of drug-loaded micelles based on well-defined PMPC-b-PBMA copolymer.

Well-defined amphiphilic diblock copolymers with different poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) content were successfully synthesized via RAFT polymerization technology. The structure of the copolymers was confirmed using GPC, 1H NMR and FTIR. The polymers have very low critical micelles concentration (6.32 x 10(-7) mol/L to 1.01 x 10(-6) mol/L), which indicates their high thermodynamic stability needed for intravenous injection. Blank and paclitaxel-loaded polymeric micelles were prepared from the PMPC-b-PBMA copolymers using self-emulsion/evaporation method. TEM analysis revealed a regular spherical shape, small diameter (less than 30 nm) and narrow size distribution of the micelles. The paclitaxel-loaded polymeric micelles had high loading content (above 13%). In vitro release kinetics of paclitaxel from the micelles was also investigated. Less than 30% of the paclitaxel was released within 320 h and the increase of the length of PMPC leads to slower release rate.