Leong K F, Chua C K, Sudarmadji N, Yeong W Y
Rapid Prototyping Laboratory, School of Mechanical and Aerospace Engineering, Nanyang Technological University, North Spine, 50 Nanyang Avenue, Singapore 639798, Singapore.
J Mech Behav Biomed Mater. 2008 Apr;1(2):140-52. doi: 10.1016/j.jmbbm.2007.11.002. Epub 2007 Nov 17.
Tissue Engineering (TE) aims to create biological substitutes to repair or replace failing organs or tissues due to trauma or ageing. One of the more promising approaches in TE is to grow cells on biodegradable scaffolds, which act as temporary supports for the cells to attach, proliferate and differentiate; after which the scaffold will degrade, leaving behind a healthy regenerated tissue. Tissues in nature, including human tissues, exhibit gradients across a spatial volume, in which each identifiable layer has specific functions to perform so that the whole tissue/organ can behave normally. Such a gradient is termed a functional gradient. A good TE scaffold should mimic such a gradient, which fulfils the biological and mechanical requirements of the target tissue. Thus, the design and fabrication process of such scaffolds become more complex and the introduction of computer-aided tools will lend themselves well to ease these challenges. This paper reviews the needs and characterization of these functional gradients and the computer-aided systems used to ease the complexity of the scaffold design stage. These include the fabrication techniques capable of building functionally graded scaffolds (FGS) using both conventional and rapid prototyping (RP) techniques. They are able to fabricate both continuous and discrete types of FGS. The challenge in fabricating continuous FGS using RP techniques lies in the development of suitable computer aided systems to facilitate continuous FGS design. What have been missing are the appropriate models that relate the scaffold gradient, e.g. pore size, porosity or material gradient, to the biological and mechanical requirements for the regeneration of the target tissue. The establishment of these relationships will provide the foundation to develop better computer-aided systems to help design a suitable customized FGS.
组织工程（TE）旨在制造生物替代品，以修复或替换因创伤或衰老而受损的器官或组织。组织工程中一种更具前景的方法是在可生物降解的支架上培养细胞，该支架作为细胞附着、增殖和分化的临时支撑；之后支架将降解，留下健康的再生组织。自然界中的组织，包括人体组织，在空间体积上呈现梯度，其中每个可识别的层都有特定的功能要执行，以便整个组织/器官能够正常运作。这样的梯度被称为功能梯度。一个好的组织工程支架应该模仿这种梯度，以满足目标组织的生物学和力学要求。因此，这种支架的设计和制造过程变得更加复杂，而引入计算机辅助工具将非常有助于缓解这些挑战。本文综述了这些功能梯度的需求和特性，以及用于缓解支架设计阶段复杂性的计算机辅助系统。这些系统包括能够使用传统和快速成型（RP）技术制造功能梯度支架（FGS）的制造技术。它们能够制造连续和离散类型的FGS。使用RP技术制造连续FGS的挑战在于开发合适的计算机辅助系统，以促进连续FGS的设计。一直缺少的是将支架梯度（例如孔径、孔隙率或材料梯度）与目标组织再生的生物学和力学要求相关联的适当模型。建立这些关系将为开发更好的计算机辅助系统提供基础，以帮助设计合适的定制FGS。
