Feng Z, Yamato M, Akutsu T, Nakamura T, Okano T, Umezu M
Department of Bio-System Engineering, Faculty of Engineering, Yamagata University, Yonezawa, Japan.
Artif Organs. 2003 Jan;27(1):84-91. doi: 10.1046/j.1525-1594.2003.07187.x.
In this article the mechanical properties of contracted collagen gels were investigated thoroughly by means of uniaxial tensile test. Large type I collagen-Dulbecco's Modified Eagle Medium (DMEM) gels (each was 26 ml in volume, 1.67 mg/ml collagen concentration), each populated with about 2.5 x 106 human fibroblasts, were made in 100 mm diameter plastic dishes precoated with albumin for floating the gels in DMEM. Such identically treated gels were divided into three groups for the mechanical measurements at different culture periods (2, 4, and 10 weeks). Rapid contraction occurred within the first 3 days and then the contraction went slowly in the rest period until it reached about 13% of its original size. The stress-strain curve of the contracted collagen gels demonstrated an exponential behavior at low stress region, followed by linear region, a point of yielding, and finally an ultimate stress point at which the maximum stress was reached. The mechanical strength increased in the first few weeks and then decreased as the culture went on. It is obvious that the collagen fibrils formed and were forced to orientate to the tensile direction after the test. The stress relaxation and cyclic creep phenomena were observed. Based on the morphological analysis of transmission electron microscopy (TEM) of the gels, a nonlinear visco-elastic-plastic constitutive formula was proposed, which was able to reproduce the rheological phenomena of the gels. This experiment shows that the human fibroblasts significantly contracted collagen gels so as to achieve certain mechanical strength, which makes it possible to be a scaffold for tissue engineering. However, a further method to reinforce the mechanical strength by several folds must be considered. Meanwhile, the rheological phenomena should be taken into account in the fabrication and application of the structure.
在本文中，通过单轴拉伸试验对收缩胶原蛋白凝胶的力学性能进行了深入研究。在预先涂有白蛋白的100毫米直径塑料培养皿中制备大型I型胶原蛋白-杜尔贝科改良伊格尔培养基（DMEM）凝胶（每块体积为26毫升，胶原蛋白浓度为1.67毫克/毫升），每块凝胶接种约2.5×10⁶个人类成纤维细胞，以便将凝胶漂浮在DMEM中。将经过相同处理的凝胶分为三组，在不同培养时期（2周、4周和10周）进行力学测量。在最初3天内迅速发生收缩，然后在剩余时间内收缩缓慢，直至达到其原始大小的约13%。收缩胶原蛋白凝胶的应力-应变曲线在低应力区域呈现指数行为，随后是线性区域、屈服点，最后是达到最大应力的极限应力点。力学强度在最初几周增加，然后随着培养的进行而降低。显然，试验后形成了胶原纤维并被迫沿拉伸方向排列。观察到了应力松弛和循环蠕变现象。基于凝胶的透射电子显微镜（TEM）形态分析，提出了一个非线性粘弹性-塑性本构公式，该公式能够再现凝胶的流变现象。本实验表明，人类成纤维细胞显著收缩胶原蛋白凝胶以达到一定的力学强度，这使其有可能成为组织工程的支架。然而，必须考虑进一步将力学强度提高几倍的方法。同时，在结构的制造和应用中应考虑流变现象。
