Preparation and Characterization of Nimodipine-loaded Methoxy Poly （ethylene glycol） -poly （lactic acid） Diblock Copolymer Nanoparticles

Amphiphilic diblock copolymers, methoxy poly （ ethylene glycol）-poly（lactic acid） （MePEG-PLA）, were synthesized from monomers of DL-lactide and methoxy poly （ethylene glycol） by a ring opening bulk polymerizatiou in the presence of stannous octoate. Their chemical structure and physical properties were investigated using FTIR, NMR, GPC, and fluorescence spectroscopy. To estimate the feasibility as colloidal drug carrier, nimodipine （ND） was loaded into MePEG-PLA block copolymer nanoparticles by phaseseparation/dialysis method. The mean diameter and drug loading efficiency of ND-loaded MePEG-PLA copolymer nanoparticles depended ou PLA/MePEG block composition of the copolymer and drug/polymer feed ratio in preparatiou. NMR study confirmed that nimodipine was entrapped into the hydrophobic inner core of MePEG-PLA copolymer nanoparticles and hydrophilic PEG chains were located ou the surface of the drug-loaded polymer nanoparticles. In vitro release experiments exhibited the sustained release behavior of nimodipine from MePEG-PLA copolymer nanoparticles, without any burst effect.