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

• Therapeutic monoclonal antibody loaded MPEG-PCL-MPEG microspheres were prepared for the first time.
• Presence of MPEG segment enhanced encapsulation efficiency of microspheres.
• Presence of MPEG in the microspheres achieved control of IgG release rate.
• MPEG in microspheres protected IgG from denaturation during γ-irradiation.
• Bioactivity of released IgG was mostly protected for 90 days.

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.

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