Oomen P J A, van Kelle M A J, Oomens C W J, Bouten C V C, Loerakker S
Department of Biomedical Engineering, Eindhoven University of Technology, 5600MB Eindhoven, Netherlands; Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600MB Eindhoven, Netherlands.
Department of Biomedical Engineering, Eindhoven University of Technology, 5600MB Eindhoven, Netherlands; Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600MB Eindhoven, Netherlands.
J Mech Behav Biomed Mater. 2017 Oct;74:438-447. doi: 10.1016/j.jmbbm.2017.07.009. Epub 2017 Jul 5.
One of the hallmarks of biological soft tissues is their capacity to grow and remodel in response to changes in their environment. Although it is well-accepted that these processes occur at least partly to maintain a mechanical homeostasis, it remains unclear which mechanical constituent(s) determine(s) mechanical homeostasis. In the current study a nondestructive mechanical test and a two-step inverse analysis method were developed and validated to nondestructively estimate the mechanical properties of biological tissue during tissue culture. Nondestructive mechanical testing was achieved by performing an inflation test on tissues that were cultured inside a bioreactor, while the tissue displacement and thickness were nondestructively measured using ultrasound. The material parameters were estimated by an inverse finite element scheme, which was preceded by an analytical estimation step to rapidly obtain an initial estimate that already approximated the final solution. The efficiency and accuracy of the two-step inverse method was demonstrated on virtual experiments of several material types with known parameters. PDMS samples were used to demonstrate the method's feasibility, where it was shown that the proposed method yielded similar results to tensile testing. Finally, the method was applied to estimate the material properties of tissue-engineered constructs. Via this method, the evolution of mechanical properties during tissue growth and remodeling can now be monitored in a well-controlled system. The outcomes can be used to determine various mechanical constituents and to assess their contribution to mechanical homeostasis.
生物软组织的一个显著特征是它们能够根据环境变化进行生长和重塑。尽管人们普遍认为这些过程至少部分是为了维持机械稳态，但仍不清楚是哪种机械成分决定了机械稳态。在当前的研究中，开发并验证了一种无损力学测试和两步反分析方法，以无损估计组织培养过程中生物组织的力学性能。通过对生物反应器内培养的组织进行充气测试来实现无损力学测试，同时使用超声无损测量组织的位移和厚度。材料参数通过逆有限元方案进行估计，在此之前有一个解析估计步骤，以快速获得已经接近最终解的初始估计。在具有已知参数的几种材料类型的虚拟实验中证明了两步反演方法的效率和准确性。使用聚二甲基硅氧烷（PDMS）样品来证明该方法的可行性，结果表明所提出的方法与拉伸测试产生了相似的结果。最后，该方法被应用于估计组织工程构建体的材料特性。通过这种方法，现在可以在一个良好控制的系统中监测组织生长和重塑过程中力学性能的演变。这些结果可用于确定各种机械成分并评估它们对机械稳态贡献。
