Lee J M, Corrente R, Haberer S A
Centre for Biomaterials, University of Toronto, Ontario, Canada.
J Biomed Mater Res. 1989 May;23(5):477-89. doi: 10.1002/jbm.820230503.
Our previous article suggested that control of the extensibility of aldehyde-fixed pericardium could be achieved by controlling shrinkage during fixation. Therefore, to prevent shrinkage, we have used sandpaper-lined plexiglass plates to clamp circular samples of bovine pericardium during fixation in glutaraldehyde, tethering them at their original dimensions. As well, we have applied transmural pressures of 50 or 100 mm Hg during fixation using a hydraulic column of glutaraldehyde solution. Strips cut at 0 degree, 30 degrees, 60 degrees, and 90 degrees to the base-to-apex cardiac direction have been examined for cyclic stress-strain response, stress relaxation, plastic deformation, and fracture behavior. Under physiological stresses, tethered and pressure-fixed materials were both nearly isotropic. Tethering during fixation produced a material with extensibility nearly identical to that of fresh tissue. Plastic deformation during cyclic loading was reduced below that seen in simple fixation while stress relaxation was unchanged. Pressure-fixation produced reduced extensibility similar to that produced in porcine aortic valve leaflets. Plastic deformation and stress relaxation were both markedly reduced. Pressure-fixation reduced the strain at fracture, but fracture behavior was otherwise unaffected. Tethering and pressure-fixation offer attractive means to control the mechanical behavior of bovine xenograft materials.
我们之前的文章表明，通过控制醛固定心包在固定过程中的收缩，可以实现对其可扩展性的控制。因此，为防止收缩，我们在戊二醛固定过程中使用衬有砂纸的有机玻璃板夹住牛心包的圆形样本，将其固定在原始尺寸。此外，我们在固定过程中使用戊二醛溶液液压柱施加50或100毫米汞柱的跨壁压力。已对沿心脏基底部至心尖方向0度、30度、60度和90度切割的条带进行循环应力-应变响应、应力松弛、塑性变形和断裂行为的研究。在生理应力下，系留固定和压力固定的材料均近乎各向同性。固定过程中的系留产生了一种可扩展性与新鲜组织几乎相同的材料。循环加载过程中的塑性变形低于简单固定时的情况，而应力松弛则未改变。压力固定产生的可扩展性降低，类似于猪主动脉瓣叶中产生的情况。塑性变形和应力松弛均显著降低。压力固定降低了断裂应变，但断裂行为在其他方面未受影响。系留固定和压力固定为控制牛异种移植材料的力学行为提供了有吸引力的方法。
