Timmer Mark D, Ambrose Catherine G, Mikos Antonios G
Department of Bioengineering, Institute of Biosciences and Bioengineering, Rice University, P.O. Box 1892, MS-142, Houston, TX 77251-1892, USA.
Biomaterials. 2003 Feb;24(4):571-7. doi: 10.1016/s0142-9612(02)00368-x.
Polymeric networks of poly(propylene fumarate) (PPF) crosslinked with poly(propylene fumarate)-diacrylate (PPF-DA) are currently being investigated as an injectable, biodegradable bone cement. This study examined the effect of crosslinking density, medium pH, and the incorporation of a beta-tricalcium phosphate (beta-TCP) filler on the in vitro degradation of PPF/PPF-DA. Cylindrical specimens were submerged in buffered saline at 37 degrees C and the change in weight, geometry, and compressive mechanical properties were monitored over a 52-week period. All formulations showed an initial increase in modulus and yield strength over the first 12 weeks, achieving maxima of 1307+/-101 and 51+/-3MPa, respectively, for the beta-TCP composite. PPF/PPF-DA networks with the lower crosslinking density demonstrated the greatest degradation with a 17% mass loss. Samples in the lower buffer pH 5.0 compared to physiological pH 7.4 did not show any differences in mass loss, but exhibited a faster decrease in the compressive strength over time. The beta-TCP composites maintained their mechanical properties at the level following their initial increase. These results show that the degradation of PPF/PPF-DA networks can be controlled by the crosslinking density, accelerated at a lower pH, and prolonged with the incorporation of the beta-TCP filler.
用聚富马酸丙二醇酯二丙烯酸酯（PPF - DA）交联的聚富马酸丙二醇酯（PPF）聚合物网络目前正作为一种可注射的、可生物降解的骨水泥进行研究。本研究考察了交联密度、介质pH值以及β - 磷酸三钙（β - TCP）填料的加入对PPF/PPF - DA体外降解的影响。将圆柱形试样浸没在37℃的缓冲盐水中，在52周的时间内监测其重量、几何形状和压缩力学性能的变化。所有配方在最初的12周内模量和屈服强度均呈现初始增加，β - TCP复合材料的模量和屈服强度分别达到最大值1307±101MPa和51±3MPa。交联密度较低的PPF/PPF - DA网络降解最为显著，质量损失达17%。与生理pH值7.4相比，缓冲pH值为5.0的样品在质量损失方面没有任何差异，但随着时间的推移，其抗压强度下降得更快。β - TCP复合材料在初始增加后的水平上保持其力学性能。这些结果表明，PPF/PPF - DA网络的降解可通过交联密度来控制，在较低pH值下加速降解，而加入β - TCP填料则可延长降解时间。
