Synthesis and characterization of MeO-PEG-PLGA-PEG-OMe copolymers as drug carriers and their degradation behavior in vitro.

The objective of this study was to characterize the methylpoly (ethylene glycol)-poly (lacticacid-co-glycolicacid)-poly (ethylene-glycol) (MeO-PEG-PLGA-PEG-OMe, abbreviation as PELGE) copolymers as intravenous injection drug delivery carriers and their degradation behavior in vitro. A series of MeO-PEG-PLGA-PEG-OMe copolymers with various molar ratios of lactic to glycolic acid and various molecular weights and different MeO-PEG contents were synthesized by ring-opening polymerization in the presence of MeO-PEG with molar masses of 2000 and 5000, using stannous octoate as the catalyst. The hydrophilicity of PELGE copolymers, evaluated by contact angle measurements, was found to increase with an increase in their MeO-PEG contents. Methylpoly (ethylene glycol)-poly (lacticacid-co-glycolicacid) (MeO-PEG-PLGA, abbreviation as PELGA) nanoparticles and PELGE nanoparticles were prepared using the emulsion-solvent evaporation technique (o/w) with Pluronic F68 (Poloxamer 188 NF) as emulsifier in the external aqueous phase. The degradation behavior of the nanoparticles was evaluated by the lactate generation with time upon their in vitro incubation in PBS (pH 7.4). The rate of in vitro degradation of the PELGE or PELGA nanoparticles depended on their composition, increasing with an increase in the proportion of MeO-PEG or LA in the copolymer chains. The degradation rate was slower at higher lactide: glycolide ratio. The lower the molecular weight of PELGE; the higher the degradation rate of the nanoparticles.