Hatami-Marbini H, Rahimi A
School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078, United States.
School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078, United States.
J Biomech. 2015 Apr 13;48(6):1052-7. doi: 10.1016/j.jbiomech.2015.01.038. Epub 2015 Feb 2.
The collagen cross-linking is a relatively new treatment option for strengthening the cornea, delaying, and in some cases stopping the progression of keratoconus. The uniaxial tensile experiments are among the most commonly used techniques to assess the effectiveness of this therapeutic option in enhancing tensile properties. In the present study, we investigated the possible effects of hydration on stiffening effects of corneal collagen cross-linking procedure, as measured by the uniaxial tensile testing method. For this purpose, after cross-linking bovine corneas, we let the strips to dehydrate in air or swell in a solution until their thickness reached an average thickness of 0.5, 0.7, 0.9, 1.1, and 1.5 mm. Using thickness as a representative of hydration, we divided corneal strips into five different groups and measured their stress-strain behavior by conducting uniaxial tensile experiments in mineral oil. It was observed that the collagen cross-linking treatment and hydration together affect the tensile behavior of the bovine cornea. While corneal collagen cross-linking resulted in a significant increase in the tensile stress-strain response of each thickness group (P<0.01), less hydrated collagen cross-linked samples showed a significantly stiffer response (P<0.01). A master curve was found for representing the tensile behavior of the collagen cross-linked bovine cornea at different levels of hydration. The results of the present research confirmed that the amount of mechanical stiffening of the corneal collagen cross-linking, as measured by uniaxial tensile testing, strongly depends on the hydration. Therefore, it is concluded that uniaxial tensile experiments could only be used to assess stiffening effects of the collagen cross-linking treatment if the hydration of specimens is fully controlled.
胶原交联是一种相对较新的用于强化角膜、延缓并在某些情况下阻止圆锥角膜进展的治疗选择。单轴拉伸实验是评估这种治疗方法增强拉伸性能有效性时最常用的技术之一。在本研究中，我们通过单轴拉伸测试方法研究了水合作用对角膜胶原交联过程硬化效果的可能影响。为此，在对牛角膜进行交联后，我们让角膜条在空气中脱水或在溶液中膨胀，直到其厚度达到平均厚度0.5、0.7、0.9、1.1和1.5毫米。以厚度作为水合作用的代表，我们将角膜条分为五个不同组，并通过在矿物油中进行单轴拉伸实验来测量它们的应力-应变行为。观察到胶原交联处理和水合作用共同影响牛角膜的拉伸行为。虽然角膜胶原交联导致每个厚度组的拉伸应力-应变响应显著增加（P<0.01），但水合程度较低的胶原交联样品表现出明显更硬的响应（P<0.01）。发现了一条主曲线来表示不同水合水平下胶原交联牛角膜的拉伸行为。本研究结果证实，通过单轴拉伸测试测量的角膜胶原交联的机械硬化量强烈依赖于水合作用。因此，得出结论：只有在完全控制标本水合作用的情况下，单轴拉伸实验才能用于评估胶原交联治疗的硬化效果。
