Preparation of porous PLA/DBM composite biomaterials and experimental research of repair rabbit radius segmental bone defect
OBJECTIVE To fabricate a novel porous bioactive composite biomaterial consisting of poly lactic acid (PLA)-bone matrix gelatin (BMG) by using the supercritical carbon dioxide fluid technique (SC-CO2) and to evaluate its osteoinductive activity. METHODS The cortical bones selected from healthy adult donors were processed into BMG by the defatting, demineralizing, and deproteinizing processes. PLA and BMG were mixed at a volume radio of 3 : 1; then, the PLA-BMG mixed material and the pure PLA material were respectively placed in the supercritical carbon dioxide reaction kettles, and were respectively added by the NaCl particles 100-200 microm in diameter for the porosity of the materials so that the porous PLA-BMG composite material and the porous PLA composite material could be formed. The mouse osteoblast-like MC3T3-E1 cells were cultured in the dulbecco's modified eagle medium (DMEM) supplemented with 10% fetal bovine serum. Then, 20 microl of the MC3T3-E1 cell suspensions containing 2 X 10(6) cells /ml were delivered into the culturing plate (24 wells/plate) made of the different materials, which were co-cultured for 2 weeks. In the PLA-BMG group, 100 microg of the crushed PLA-BMG material was contained in each well; in the PLA group, 100 microg of the crushed PLA material was contained in each well; and in the DMEM group, only DMEM was contained, which served as the control group. There were 6 wells in each group. The quantitative analysis on the calcification area was performed by the staining of the alizarin red S. The co-cultured cells were harvested and lysated in 1 ml of 0. 2% Nonidet P-40 by the ultrasonic lysating technique. Then, the ALP activity and the Ca content were measured according to the illuminations of the reagent kits. RESULTS The porous PLA-BMG composite material showed a good homological porosity with a pore diameter of 50-150 microm and a good connectivity between the pores. The ALP activity, the Ca content, and the calcification area were significantly greater in the PLA-BMG group than in the PLA group and the control group (325.59 +/- 70.40 U/gprot, 3.51+/- 1.64 mmol/gprot, 42.98 +/- 4.44% vs. 63. 62 +/- 30.01 U/gprot, 1.04+/-0.21 mmol/gprot, 9.55+/-1.94%, and 2.40+/-1.47 U/gprot, 0.70+/-0.24 mmol/gprot, 0.86+/-0.41%; P<0.05). Meanwhile, there was a statistically significant difference between the PLA group and the control group in the ALP activity and the calcification area (P< 0.05). CONCLUSION The porous PLA-BMG composite material prepared by the use of SC-CO2 has a good osteoinductive activity and can be used as a promising bone biomaterial and a bone tissue engineered scaffold.