Adsorption of vascular endothelial growth factor to two different apatitic materials and its release

The aim of our study was to assess the ability of calcium phosphate powders to serve as growth factor carriers. Vascular endothelial growth factor (VEGF), in particular, is locally involved in the bone formation process throughout osteoblast differentiation. Two different apatitic substrates were tested: hydroxyapatite (HA), widely used as biomaterial, and nanocrystalline carbonated apatite (CA), which has a composition similar to bone mineral crystals. These materials have been compared for their VEGF adsorption and release properties. The adsorption of the growth factor was higher on CA than on HA probably due to differences of both the proteins and the powders involved. The specific activity of the VEGF released was also tested to determine the available activity for cells in contact with these materials. Interestingly, the bioactivity of the VEGF released from CA quantified on fetal bovine aortic endothelial cells (FBAE) by evaluating the proliferation activity, exhibited no marked difference compared to native VEGF. Qualitatively, VEGF adsorbed on CA material induced well-defined collagen type I immunostaining on osteoblast cells compared to the staining obtained after VEGF adsorption on HA.