Characteristics and release profiles of MPEG-PCL-MPEG microspheres containing immunoglobulin G.

Polyester-polyether type block copolymers have attracted attention in the area of drug delivery systems with their capability in providing a broad range of amphiphilic characteristics. The aim of the present work was to prepare and characterize immunoglobulin G (IgG) loaded methoxy poly(ethylene glycol)-poly(ɛ-caprolactone)-methoxy poly(ethylene glycol) (MPEG-PCL-MPEG) microspheres as potential carrier for therapeutic monoclonal antibodies used in clinics. MPEG-PCL-MPEG triblock copolymer was synthesized by ring-opening polymerization of ɛ-caprolactone initiated by MPEG and then characterized. Microspheres were prepared by double emulsion-solvent evaporation method and their properties were compared with those of PCL microspheres. Microspheres had spherical shape with a mean particle size around 6 μm. MPEG-PCL-MPEG microspheres had higher encapsulation efficiency than PCL microspheres. After 90 days of release, 30±2% and 57±3% of the bioactivity of IgG released from non-irradiated PCL and MPEG-PCL-MPEG microspheres were protected, respectively. Presence of MPEG in microspheres provided more controlled IgG release rate and protected IgG from denaturation during γ-irradiation (20±3% and 49±2% for PCL and MPEG-PCL-MPEG microspheres, respectively). In vitro cytotoxicity tests revealed that both MPEG-PCL-MPEG and PCL microspheres had no toxic effect on cells. This study showed that MPEG-PCL-MPEG microspheres are promising delivery systems for therapeutic monoclonal antibodies.