The purpose of this study was to synthesize a novel Wound dressing containing bFGF-loaded microspheres for promoting healing and tissue regeneration. Gelatin was chosen as the underlying layer and was prepared in porous sponge. As the external layer, elastomeric polyurethane membranes were used. bFGF was loaded in microspheres to achieve prolonged release for higher efficiency. The microspheres were characterized for particle size, in vitro protein release, and bioactivity. The dressings were tested in in vivo experiments on skin defects created on pigs. At certain intervals, wound areas were measured and tissues from wound areas were biopsied for histological examinations. Average size of the microspheres was 14.36 +/- 3.56 mu m and the network sponges were characterized with an average pore size of 80-160 mu m. Both the release efficiency and the protein bioactivity revealed that bFGF was released in a controlled manner and was biologically active, as assessed by its ability to induce the proliferation of fibroblasts. The rate of wound-area decrease was much faster and the quality of the newly-formed dermis was almost as good as the normal skin. The application of this novel bilayer wound dressing provided an optimum healing milieu for the proliferating cells and regenerating tissues. (c) 2006 Wiley Periodicals, Inc.