Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland, 20993.
Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, 03755.
J Biomed Mater Res B Appl Biomater. 2018 Aug;106(6):2393-2402. doi: 10.1002/jbm.b.34045. Epub 2017 Nov 27.
Liners used in orthopedic devices are often made from ultrahigh molecular weight polyethylene (UHMWPE). A general predictive capability for transport coefficients of small molecules in UHMWPE does not exist, making it difficult to assess properties associated with leaching or uptake of small molecules. To address this gap, we describe here how a form of the Vrentas-Duda free volume model can be used to predict upper-bound diffusion coefficients (D) of arbitrary molecules within UHMWPE on the basis of their size and shape. Within this framework, the free-volume microstructure of UHMWPE is defined by analysis of a curated set of model diffusants. We determined an upper limit on D for vitamin E, a common antioxidant added to UHMWPE, to be 7.1 × 10 cm s . This means that a liner that contains 0.1 wt % or less Vitamin E and has <120 cm patient contacting surface area would elute <100 µg/day of vitamin E. Additionally, the model predicts that squalene and cholesterol-two pro-oxidizing biological compounds-do not penetrate over 820 µm into UHMWPE liners over the course of 5 years because their D is ≤7.1 × 10 cm s . © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2393-2402, 2018.
用于矫形设备的衬里通常由超高分子量聚乙烯（UHMWPE）制成。目前还没有预测小分子在 UHMWPE 中输运系数的通用方法，因此难以评估与小分子浸出或吸收相关的性质。为了解决这一差距，我们在这里描述了如何使用 Vrentas-Duda 自由体积模型的一种形式，根据小分子的大小和形状来预测 UHMWPE 中任意分子的上限扩散系数（D）。在这个框架内，通过对一组经过精心挑选的模型扩散剂的分析来定义 UHMWPE 的自由体积微结构。我们确定了维生素 E 的扩散系数的上限值为 7.1×10cm ²/s，维生素 E 是一种常见的添加到 UHMWPE 中的抗氧化剂。这意味着，含有 0.1wt%或更少维生素 E 的衬里，且与患者接触的表面积<120cm ²，每天的维生素 E 浸出量<100µg。此外，该模型还预测，角鲨烯和胆固醇——两种促氧化的生物化合物——在 5 年内不会穿透超过 820µm 进入 UHMWPE 衬里，因为它们的 D 值≤7.1×10cm ²/s。©2017WileyPeriodicals，Inc. J Biomed Mater Res Part B：Appl Biomater，106B：2393-2402，2018。
