Siegmund Thomas, Allen Matthew R, Burr David B
School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA.
J Biomech. 2008;41(7):1427-35. doi: 10.1016/j.jbiomech.2008.02.017. Epub 2008 Apr 11.
Experimental evidence demonstrates that collagen cross-linking in bone tissue significantly influences its deformation and failure behavior yet difficulties exist in determining the independent biomechanical effects of collagen cross-linking using in vitro and in vivo experiments. The aim of this study is to use a nano-scale composite material model of mineral and collagen to determine the independent roles of enzymatic and non-enzymatic cross-linking on the mechanical behavior of a mineralized collagen fibril. Stress-strain curves were obtained under tensile loading conditions without any collagen cross-links, with only enzymatic cross-links (modeled by cross-linking the end terminal position of each collagen domain), or with only non-enzymatic cross-links (modeled by random placement of cross-links within the collagen-collagen interfaces). Our results show enzymatic collagen cross-links have minimal effect on the predicted stress-strain curve and produce a ductile material that fails through debonding of the mineral-collagen interface. Conversely, non-enzymatic cross-links significantly alter the predicted stress-strain response by inhibiting collagen sliding. This inhibition leads to greater load transfer to the mineral, which minimally affects the predicted stress, increases modulus and decreases post-yield strain and toughness. As a consequence the toughness of bone that has more non-enzymatically mediated collagen cross-links will be drastically reduced.
实验证据表明，骨组织中的胶原蛋白交联显著影响其变形和破坏行为，但利用体外和体内实验确定胶原蛋白交联的独立生物力学效应存在困难。本研究的目的是使用矿物质和胶原蛋白的纳米级复合材料模型，以确定酶促交联和非酶促交联对矿化胶原纤维力学行为的独立作用。在无任何胶原蛋白交联、仅存在酶促交联（通过交联每个胶原结构域的末端位置进行模拟）或仅存在非酶促交联（通过在胶原-胶原界面内随机放置交联进行模拟）的拉伸加载条件下获得应力-应变曲线。我们的结果表明，酶促胶原蛋白交联对预测的应力-应变曲线影响最小，并产生一种通过矿化胶原界面脱粘而破坏的韧性材料。相反，非酶促交联通过抑制胶原蛋白滑动显著改变预测的应力-应变响应。这种抑制导致更多的载荷传递到矿物质上，这对预测应力影响最小，增加了模量，降低了屈服后应变和韧性。因此，具有更多非酶介导的胶原蛋白交联的骨的韧性将大幅降低。
