Jeong Joonsoo, Hyun Bae So, Seo Jong-Mo, Chung Hum, June Kim Sung
Department of Electrical & Computer Engineering, Seoul National University, Seoul 151-742, Korea.
J Neural Eng. 2016 Apr;13(2):025004. doi: 10.1088/1741-2560/13/2/025004. Epub 2016 Feb 23.
The aim of this study is to evaluate the long-term reliability of a recently presented liquid crystal polymer (LCP) -based retinal prosthesis in vitro as well as in vivo. Because an all-polymer implant introduces another intrinsic leak type due to gas permeation, for which the traditional helium leak test for metallic packages was not designed to quantify, a new method to investigate its durability is required.
We designed and carried out a series of reliability tests specifically for all-polymer implants by quantitatively investigating moisture ingress through various pathways of the polymer surface, and the polymer-polymer and polymer-metal adhesions. Moisture permeation through the bulk material was estimated by analytic calculation, while water ingress through the adhesively sealed LCP-LCP and LCP-metal interfaces was investigated using the separate parts of an electrode array and a package in an accelerated aging condition. In vivo tests were done in rabbits to examine the long-term biocompatibility and implantation stability by fundus observation and optical coherence tomography (OCT) imaging.
The analytic calculation estimated good barrier properties of the LCP. Samples of the LCP-based electrode array failed after 114 days in 87 °C saline as a result of water penetration through the LCP-metal interface. An eye-conformable LCP package survived for 87 days in an accelerated condition at 87 °C. The in vivo results confirmed that no adverse effects were observed around the retina 2.5 years after the implantation of the device.
These long-term evaluation results show the potential for the chronic use of LCP-based biomedical implants to provide an alternative to traditional metallic packages.
本研究旨在评估一种最近推出的基于液晶聚合物（LCP）的视网膜假体在体外和体内的长期可靠性。由于全聚合物植入物因气体渗透引入了另一种内在泄漏类型，而传统的金属封装氦泄漏测试并非设计用于量化这种泄漏，因此需要一种新的方法来研究其耐久性。
我们通过定量研究水分通过聚合物表面的各种途径以及聚合物 - 聚合物和聚合物 - 金属粘附的进入情况，专门为全聚合物植入物设计并进行了一系列可靠性测试。通过解析计算估计水分在块状材料中的渗透，而在加速老化条件下，使用电极阵列和封装的单独部分研究水分通过粘结密封的LCP - LCP和LCP - 金属界面的进入情况。在兔子身上进行体内测试，通过眼底观察和光学相干断层扫描（OCT）成像来检查长期生物相容性和植入稳定性。
解析计算估计LCP具有良好的阻隔性能。基于LCP的电极阵列样品在87°C盐水中114天后因水分通过LCP - 金属界面渗透而失效。符合眼睛形状的LCP封装在87°C的加速条件下存活了87天。体内结果证实，在植入该装置2.5年后，视网膜周围未观察到不良影响。
这些长期评估结果表明基于LCP的生物医学植入物长期使用的潜力，可为传统金属封装提供替代方案。
