Adsorption and release behaviors of vascular endothelial growth factor on porous hydroxyapatite ceramic under competitive conditions

Vascular endothelial growth factor plays a positive role in the vascularization of bone grafts after implantation. In the present study, we constructed a multi-protein system and investigated its adsorption and release on porous hydroxyapatite ceramic under competitive conditions, and we also evaluated its bioactivity by cells proliferation experiments after it released from the ceramic. The results showed that vascular endothelial growth factor always had a high adsorption on porous hydroxyapatite ceramic, whether having the inhibition of other serum proteins or not. When incubated in the cell culture medium containing 10% fetal calf serum, the pre-loaded vascular endothelial growth factor showed a slow and sustained release from the ceramic. After 7 days of incubation, its accumulative release rate was only about 50%. The high adsorption and slow release of vascular endothelial growth factor on porous hydroxyapatite ceramic should be ascribed to the strong electrostatic attraction between them as well as the abundant nano-sized micropores present on the ceramic surface. The cell culture experiments confirmed that the released vascular endothelial growth factor from porous hydroxyapatite ceramic could promote the proliferation of human umbilical vein endothelial cells significantly, indicating that its bioactivity was still maintained after desorbing from the ceramic. As thus, it could be inferred that porous hydroxyapatite ceramic may adsorb and accumulate the endogenous vascular endothelial growth factor at the early implantation stage, which then releases from the ceramic surface gradually and takes effect on the ingrown vascular endothelial cells, leading to the rapid vascularization of the implant.