Growth factor-loaded scaffolds for bone engineering

The objective of the study presented here was to investigate the bone inductive properties as well as release kinetics of rhTGF-beta1- and rhBMP-2-loaded Ti-fiber mesh and CaP cement scaffolds. Therefore, Ti-fiber mesh and porous CaP cement scaffolds were provided with these growth factors and inserted in subcutaneous and cranial implant locations in rats and rabbits. In vitro, a rapid release of rhTGF-beta1 was observed during the first 2 h of the Ti-fiber mesh scaffolds. During this time, more than 50% of the total dose of rhTGF-beta1 was released. Following this initial peak, a decline in the level of rhTGF-beta1 occurred. After 1 week, the entire theoretical initial dose was observed to have been released. This in contrast to the rhTGF-beta1 and rhBMP-2 release of the porous CaP cement scaffolds. Here, no substantial initial burst release was observed. The scaffolds showed an initial release of about 1% after 1 day, followed by an additional marginal release after 1 week. Histological analysis revealed excellent osteoconductive properties of non-loaded Ca-P material. Inside non-loaded Ti-mesh fiber scaffolds, also bone ingrowth occurred. Quantification of the bone ingrowth showed that bone formation was increased significantly in all scaffold materials by administration of rhTGF-beta1 and rhBMP-2. Consequently, we conclude that the release kinetics of growth factors from porous CaP cement differs from other scaffold materials, like metals and polymers. Nevertheless, orthotopic bone formation in a rabbit cranial defect model was stimulated in rhTGF-beta1- and rhBMP-2-loaded CaP cement and Ti-fiber mesh scaffolds compared with non-loaded implants.