AIM  To prepare delayed-aciton microspheres for the sirolimus using the polymers poly(3-hydroxybutyrate-co-3-hydroxyvalerate),in order to provide a foundation for prevention and treatment of immunological rejection following corneal transplantation.
METHODS  The microspheres preparation applied orthogonal experimental design and water in oil(o/w) emulsion-solvent evaporation method. To optimize the preparation technology, microspheres’ both drug loading rate and entrapment rate were measured and were integrated with its observation of morphological characteristic. Then, the experimental results were applied to the aqueous humor simulation environment for detecting in vitro delayed-action properties.
RESULTS  The preparation technology demonstrated a stable and feasible prospect. The microspheres presented smooth and spherical surfaces with (37.34±1.25)% drug loading rate and (99.63±0.93) % entrapment rate, which enabled the delayed actions of the drug in vitro and for 500h accumulated release percentage were reached to 71%.
CONCLUSION  With the characteristics of well superficial syndrome, high drug loading rate and entrapment rate, the sirolimus loaded delayed–action microspheres might play stable and delayed–action performance of clinical effects.