Stability of prostaglandin E2 (PGE2) embedded in poly-d,l-lactide-co-glycolide microspheres: a pre-conditioning approach for tissue engineering applications

Prostaglandin E 2 (PGE 2 ) is involved in angiogenesis, bone repair and cartilage metabolism. Thus, PGE 2 might represent a suitable signaling molecule in different tissue engineering applications. PGE 2 also has a short half-life time. Its incorporation into poly- d , l -lactide-co-glycolide (PLGA) microspheres was demonstrated in a previous study. However, the stability of bioactive PGE 2 in these microspheres is unknown. With an adjusted mass spectrometry assay we investigated the amount of incorporated PGE 2 and the stability of PGE 2 in conventional cell culture medium and in PLGA microspheres. The stability of PGE 2 was closely pH dependent. Strong acidic or basic environments reduced the half-life from 300 h (pH 2.6–4.0) to below 50 h at pH 2.0 or pH 8.8. The half-life of PGE 2 incorporated into poly- d , l -lactide-co-glycolide increased drastically to 70 days at 37°C and to 300 days at 8°C. Analysis with scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrated a distinct nanostructure of the polymeric phase and both nano- and microporosity.