Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2V4, Canada.
IEEE Trans Biomed Eng. 2013 Jun;60(6):1667-76. doi: 10.1109/TBME.2013.2241061. Epub 2013 Jan 23.
We report the development of a surrogate spinal cord for evaluating the mechanical suitability of electrode arrays for intraspinal implants. The mechanical and interfacial properties of candidate materials (including silicone elastomers and gelatin hydrogels) for the surrogate cord were tested. The elastic modulus was characterized using dynamic mechanical analysis, and compared with values of actual human spinal cords from the literature. Forces required to indent the surrogate cords to specified depths were measured to obtain values under static conditions. Importantly, to quantify surface properties in addition to mechanical properties normally considered, interfacial frictional forces were measured by pulling a needle out of each cord at a controlled rate. The measured forces were then compared to those obtained from rat spinal cords. Formaldehyde-crosslinked gelatin, 12 wt% in water, was identified as the most suitable material for the construction of surrogate spinal cords. To demonstrate the utility of surrogate spinal cords in evaluating the behavior of various electrode arrays, cords were implanted with two types of intraspinal electrode arrays (one made of individual microwires and another of microwires anchored with a solid base), and cord deformation under elongation was evaluated. The results demonstrate that the surrogate model simulates the mechanical and interfacial properties of the spinal cord, and enables in vitro screening of intraspinal implants.
我们报告了一种替代脊髓的开发，用于评估用于脊髓内植入的电极阵列的机械适用性。对候选材料（包括硅酮弹性体和明胶水凝胶）的替代脊髓的机械和界面特性进行了测试。使用动态力学分析对弹性模量进行了表征，并与文献中实际人体脊髓的值进行了比较。测量了使替代脊髓压入指定深度所需的力，以获得静态条件下的值。重要的是，为了除通常考虑的机械性能之外定量地描述表面性能，通过以受控的速率从每个脊髓中拉出一根针来测量界面摩擦力。然后将测量到的力与从大鼠脊髓中获得的力进行比较。在水中质量分数为 12wt%的甲醛交联明胶被确定为构建替代脊髓的最适合材料。为了证明替代脊髓在评估各种电极阵列行为中的实用性，将两种类型的脊髓内电极阵列（一种由单个微丝制成，另一种由带有固体基底的微丝固定）植入脊髓内，并评估了伸长过程中脊髓的变形。结果表明，该替代模型模拟了脊髓的机械和界面特性，并能够对脊髓内植入物进行体外筛选。
