Synthesis, Characterization Of Star-shaped PLA-b-PEG Copolymer And Its Application In Drug Delivery

Star-shaped polylactide (PLA) and two types of amphiphilic star-shaped block copolymers, sPDLLA-b-PEG with star-shaped PDLLA as the core and PEG as the arms while sPEG-b-PLLA with star-shaped PEG as the core and PLLA as the arms, were made through ring-opening polymerization. Ibuprofen (IBU) loaded polymeric micro-spheres based on the synthesized polymer above were prepared and the drug-encapsulating properties and the in vitro releasing properties were also studied.Four-arm star-shaped poly(D,L-lactide) were synthesized through melt polymerization from D,L-lactide and pentaerythritol (PETH). The influence of the reaction condition, including reaction temperature, time, catalyst and monomer ratio, on the molecular weight of sPDLLA was studied. And the structure of products were confirmed by FT-IR and 1H-NMR.sPDLLA-b-PEG were prepared from sPDLLA and carboxyl-terminated poly(ethylene glycol) methyl ether (CT-mPEG) with varied molecular weight, and sPEG-b-PLLA were synthesized form L-lactide and sPEG with varied molecular weight and arms. The synthesized product were characterized by FT-IR,1H-NMR,GPC,DSC,XRD and contact angle analysis, and the results confirmed the structures of the two block copolymers. It was also found that compared with PLA, the hydrophilical properties of the copolymers were distinctly improved.Three types of ibuprofen loaded micro-spheres based on the above three types of polymers, i.e., IBU/PLLA, IBU/sPLLA, IBU/sPEG-b-PLLA micro-spheres were prepared using the method of solvent evaporation, and the optimized preparation technology were obtained via orthogonal experiments, and the drug-encapsulating properties and in vitro drug-releasing properties were studied. The results showed that compared with IBU/PLLA micro-sphere, the drug encapsulate efficiency of IBU/sPLLA and IBU/sPEG-b-PLLA micro-sphere were higher and the in vitro drug releasing rate were slowed down, which mainly due to the faster degradation of sPLLA and sPEG-b-PLLA for the star-shaped structure and the block copolymerization of sPEG. The drug releasing curves of these three types of micro-spheres could be fit by first-order equation, and the releasing mechanism were non-Fickian diffusing, i.e., the synergetic effect of polymer degradation and drug diffusing.