Preparation and cytotoxicity of poly (DL-lactide-co-glycolide) microspheres encapsulating 2-methoxyestradiol

Injectable implant would be a potential way for 2-methoxyestradiol (2-ME) for the therapy of breast cancer because of its water-insolubility, short half-life, and low oral bioavailability. So 2-ME microspheres based on poly (DL-lactide-co-glycolide) were prepared by emulsion solvent extraction method and characterized for morphology, particle size, drug physical state, entrapment efficiency and drug release in vitro and in vivo. Their cytotoxicity on MCF-7 cells was evaluated by sulforhodamine B (SRB) method. The 2-ME was successfully entrapped in the interior of microspheres with particle size of 55.44 ± 12.21 μm and could exist in an amorphism. In vitro and in vivo release of 2-ME from the microspheres occurred in a Ritger-Peppas and zero-order manner with a slow release over 46 days, respectively, and their better correlation was found. The 2-ME even with very low concentration in the microspheres could efficiently inhibit the growth of MCF-7 cells compared to the equivalent amount of drug in free solution, which indicated that the release rate from the microspheres and local water-solubility of 2-ME could maintain effective drug concentration in target site. The above results indicated that the microspheres prepared could not only control prolonged release of 2-ME in vitro and in vivo but also maintain effective drug concentration in target site. So 2-ME microspheres are acceptable for controlled release devices for effective treatment of breast cancer.