Cambridge University Engineering Department, Trumpington St., CB2 1PZ Cambridge, UK.
J Mech Behav Biomed Mater. 2012 Jul;11:16-26. doi: 10.1016/j.jmbbm.2011.10.003. Epub 2011 Oct 18.
Tissue engineering offers a paradigm shift in the treatment of back pain. Engineered intervertebral discs could replace degenerated tissue and overcome the limitations of current treatments, which substantially alter the biomechanical properties of the spine. The centre of the disc, the nucleus pulposus, is an amorphous gel with a large bound water content and it can resist substantial compressive loads. Due to similarities in their compositions, hydrogels have frequently been considered as substitutes for the nucleus pulposus. However, there has been limited work characterising the time-dependent mechanical behaviour of hydrogel scaffolds for nucleus pulposus tissue engineering. Poroelastic behaviour, which plays a key role in nutrient transport, is of particular importance. Here, we investigate the time-dependent mechanical properties of gelatin and agar hydrogels and of gelatin-agar composites. The time-dependent properties of these hydrogels are explored using viscoelastic and poroelastic frameworks. Several gel formulations demonstrate comparable equilibrium elastic behaviour to the nucleus pulposus under unconfined compression, but permeability values that are much greater than those of the native tissue. A range of time-dependent responses are observed in the composite gels examined, presenting the opportunity for targeted design of custom hydrogels with combinations of mechanical properties optimized for tissue engineering applications.
组织工程为治疗腰痛提供了一种范式转变。工程化的椎间盘可以替代退化的组织，并克服当前治疗方法的局限性，这些方法会极大地改变脊柱的生物力学特性。椎间盘的中心，即髓核，是一种具有大量结合水含量的无定形凝胶，可以抵抗很大的压缩载荷。由于其组成相似，水凝胶经常被认为是髓核的替代品。然而，对于用于髓核组织工程的水凝胶支架的时变机械行为，只有有限的工作进行了描述。在营养物质运输中起着关键作用的多孔弹性行为尤其重要。在这里，我们研究了明胶和琼脂水凝胶以及明胶-琼脂复合材料的时变机械性能。使用粘弹性和多孔弹性框架来研究这些水凝胶的时变特性。几种凝胶配方在无约束压缩下表现出与髓核相当的平衡弹性行为，但渗透率值比天然组织大得多。在所研究的复合凝胶中观察到一系列时变响应，为针对特定应用的定制水凝胶的组合设计提供了机会，这些水凝胶的机械性能可以优化。
