Delivery mode and efficacy of BMP-2 in association with implants

Bone healing may be improved in implant patients by the administration of osteogenic agents, such as bone morphogenetic protein 2 (BMP-2). But the efficacy of BMP-2 depends upon its mode of application. We hypothesized that BMP-2 is capable of a higher osteogenic efficacy when delivered physiologically, viz., when incorporated into a calcium-phosphate carrier that mimics mineralized bone matrix, than when administered via simple pharmacological modes, such as by adsorption onto a carrier surface. Using an ectopic rat model, we compared the osteoinductive efficacies of calcium-phosphate implant-coatings bearing either incorporated, adsorbed, or incorporated and adsorbed BMP-2. When adsorbed directly onto the naked implant surface, BMP-2 was not osteogenic. When adsorbed onto a calcium-phosphate coating, it was osteoinductive, but not highly efficacious. When BMP-2 was incorporated into calcium-phosphate coatings, it was a potent bone-inducer, whose efficacy was compromised, not potentiated, by the additional deposition of an adsorbed pool.