Porous beta tricalcium phosphate scaffolds used as a BMP-2 delivery system for bone tissue engineering

Macroporous beta tricalcium phosphate (beta-TCP) scaffolds were evaluated as potential carriers and delivery systems for bone morphogenetic protein-2 (BMP-2). Chemical etching was performed to increase the available surface and thus the protein loading. X-ray diffraction and infrared spectrocopy analyses confirmed the preparation of pure beta-TCP scaffolds. Scanning electron microscopy revealed interconnected porosity (64%) and a microporous surface after chemical etching. Scaffolds loaded with 30 and 15 microg of BMP-2 were implanted respectively into the back muscles and into femoral defects (condyle and diaphysis) of rabbits for 4 weeks. Histological observations confirmed the activity of the BMP-2 released from the scaffolds. Intramuscularly, bone was formed within the BMP-2-loaded scaffold pores. In the bone defects, the effect of released BMP-2 was similarly noticeable, as evaluated by histomorphometry. The incorporation of BMP-2 resulted in an amount of newly formed bone that was 1.3 times higher than with unloaded scaffolds. The implant site, however, did not have an effect on bone formation as no statistical differences were measured between cortical (diaphysis) and trabecular (condyle) defects. These results indicate the suitability of chemically etched beta-TCP scaffolds as BMP-2 carriers, in the context of bone regeneration.