The Preparation of Angiogenic Composite as Injectable Bone Cement for Femoral Head Avascular Necrosis

Avascular necrosis of the femoral head commonly occurs in the people who are thirty to fifty years old. The most general treatment for early stages of avascular necrosis of the femoral head is core decompression. However, there is no general consensus regarding either the indications for this procedure or the techniques that optimize results. We want to develop a biodegradable and angiogenic bone cement for treatment of avascular necrosis of the hip. Core decompression is followed by injection of bone cement within operation. Bone cement will provide mechanical strength and angiogenic function to increase nutrition supply for bone tissue regeneration. We anticipate the newly formed bone can replace the degraded bone cement and the defect site is able to recovered. Several advantages of poly(propylene fumarate) (PPF) has been investigated, including：biodegradable material and low crosslinking temperature. Calcium phosphate cement (CPC) is bioresorbable and osteoconductive. We combined these two key materials to offer proper mechanical strength for femoral head of patients. By addition of ginsenoside Rg1 which is extracted from panax ginseng as a angiogenic agent, anticipating that this composite can act as a mechanical support at the bone defect site and stimulate bone regeneration simultaneously. The first part of this study is mainly to discuss the influence of three different ratios of CPC to PPF on biocompatibility, mechanical strength, crosslinking temperature and swelling. Results showed bone cement was more biocompatible with increasing the ratio of CPC to PPF. Increasing the ratio of CPC to PPF also strengthened the mechanical strength, reduce the crosslinking temperature and lower swelling effect. In the second part of this study, we chose the optimal ratio of CPC to PPF and mixed them with three different amounts of Rg1. Then the drug release profile was analyzed and the function of released Rg1 was checked. Data revealed the three different ratios of Rg1 to cement shared almost the same pattern in cumulative Rg1 figure. We chose the proper ratio to make extract liquid. Angiogenic function of released Rg1 to human umbilical vein endothelial cell (HUVEC) was tested by tube formation assay within extract liquid. Result showed the released Rg1 was still able to stimulate angiogenesis signficantly. In summary, this bone cement composite possesses great developing potential to be applied on treating avascular necrosis of the femoral head.