PLGA microspheres for oral osteopenia treatment: preliminary in vitro in vivo evaluation

The aim of this work was to prepare and to evaluate in vitro/in vivo microspheres based on poly(D,L-lactide-co-glycolide) copolymers containing ipriflavone, for the local treatment of oral bone loss. The first objective was the preparation and in vitro characterization of ipriflavone loaded microspheres, by emulsion/solvent evaporation method. Process parameters such as drug:polymer weight ratio, and molecular weight of copolymers, were also investigated. The second objective was to elaborate a suitable animal model of mandibular osteoporosis, to evaluate the efficacy of these microparticulate drug delivery systems. In vivo experiments were carried out on female rats, in which oral osteopenia was induced by gonadectomy and molar avulsion. Morphometric analysis of mandibular segment were carried out to quantify the development of oral osteopenia and the efficacy of drug loaded microspheres. Results showed that ipriflavone loaded PLGA microspheres can be successfully obtained with good in vitro characteristics, utilizing the emulsification/solvent evaporation method. In vivo experiments revealed that local administration of microspheres produced only mild inflammation on the injection site. Morphometric analyses showed, at the level of the third molar, a slight increase in spongy and total bone mass on rat jaw treated with microspheres with respect to control. Control animals exhibited a scarce degree of osteopenia demonstrating that this animal model is not suitable for this purpose. (C) 2003 Elsevier Science B.V. All rights reserved.