Morphology and levonorgestrel release behavior of polycaprolactone/poly(ethylene oxide)/polylactide tri-component copolymeric microspheres

A novel polycaprolactone/poly(ethylene oxide)/polylactide (PCEL) tri-component copolymer was synthesized and used for the investigation of lipid-soluble drug levonorgestrel (LNG), in vitro release from drug-loaded microspheres. The hydrophilicity of the PCEL strongly depended on the content of the poly(ethylene oxide) (PEO) segment. LNG-loaded biodegradable polylactide (PLA) and PCEL microspheres have been successfully prepared by using an oil-in-water emulsion and solvent-evaporation method. The effect of various factors such as chemical composition and molecular weight on the morphology of the microspheres produced has been investigated. The influence of chemical composition and hydrophilicity on the drug-loading efficiency has also been investigated. The release behaviors of LNG in vitro from the PLA and PCEL microspheres were determined. The drug-loading efficiency and LNG-release behavior closely depended on the chemical composition and morphology of the polymeric microspheres. With the addition of a PEO segment in the copolymer chains, the structure of the microspheres became porous which would lower the drug-loading efficiency and speed up the drug-release rate. Copyright (C) 2003 John Wiley Sons, Ltd.