Validation of a protocol based on Raman and infrared spectroscopies to nondestructively estimate the oxidative degradation of UHMWPE used in total joint arthroplasty
Validation of a protocol based on Raman and infrared spectroscopies to nondestructively estimate the oxidative degradation of UHMWPE used in total joint arthroplasty
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DOI：
10.1016/j.actbio.2016.04.040
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发表时间：
2016-07-01
影响因子：
9.7
通讯作者：
Pezzotti, Giuseppe
中科院分区：
文献类型：
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作者：
Puppulin, Leonardo;Miura, Yoshihiro;Pezzotti, Giuseppe
事实上，高交联聚乙烯（HXLPE）的体内氧化降解仍然是影响关节置换术长期生存的限制因素之一。最近的研究明确指出，全髋关节和膝关节置换术中的新一代高交联和重熔聚乙烯部件在植入5-10年后也发生了意外氧化。研究聚乙烯（PE）氧化的标准方法依赖于红外光谱的使用，如果从一方面来说，红外光谱是检测含有羰基的氧化物质的可靠技术，另一方面，它不能区分导致链断裂和随后的聚合物机械性能劣化的羧酸部分。在本研究中，我们验证了一个新的协议的基础上拉曼光谱，这是适合于评估聚乙烯的氧化诱导的结构降解。在体外加速老化实验之后，根据ASTM标准通过红外光谱法计算的不同市售HXLPE的氧化指数（01）与通过拉曼光谱法计算的结晶相（α 1）的最严重变化明确相关。在每种材料中，01值相等的位置显示出不同程度的断链诱导的重结晶，证实红外光谱可能高估了聚合物的有效机械降解。此外，与基于红外光谱的标准相比，由于拉曼光谱的非破坏性及其高空间分辨率，这种评估氧化的新方法能够调查HXLPE组件原始表面上发生的降解。适用于评价聚乙烯氧化引起的结构降解。事实上，研究聚乙烯中氧化的标准方法依赖于红外光谱的使用，其能够检测含有羰基的氧化物质的存在，所述羰基是聚烯烃中氧化的主要产物。如果一方面这种技术能够定量分析氧化，另一方面，它不能区分的部分物种与羰基负责断链。事实上，酯、酮和羧酸是在由自由基的存在引发的氧化级联的末端通常在聚乙烯上形成的羰基的氧化产物，但只有后者负责断链和随后的机械性能劣化。根据ASTM标准获得的氧化指数与一定程度的机械劣化没有明确的相关性，但是，简单地说，具有相同数量羰基的两种回收物可能具有不同的机械性能劣化。重结晶是断链后分子量降低的直接结果。拉曼光谱（RS）是一种可行的非破坏性方法，用于评估聚乙烯中结晶相的分数，并且由于其高空间分辨率，完全适合于分析介观尺度下的微观结构改性，其中氧化的影响显现出来。本文的目的有两个：i）比较目前市场上5种不同类型的关节置换聚乙烯体外氧化引起的微观结构变化; ii）根据IR和RS结果的比较分析建立方案，以获得能够判断氧化降解引起的材料机械劣化的现象学相关性。(C)2016 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
As a matter of fact, the in vivo oxidative degradation of highly cross-linked polyethylene (HXLPE) still remains one of the limiting factors that affect the long term survivorship of joint replacements. Recent studies clearly pointed out that also the new generation of highly cross-linked and remelted polyethylene components in total hip and knee replacement underwent unexpected oxidation after 5-10 years of implantation. The standard methodology to investigate the oxidation of polyethylene (PE) relies on the use of infrared spectroscopy, which, if from one hand is a reliable technique for the detection of oxidized species containing carbonyl group, on the other hand it is not capable of discriminating the fraction of carboxyl acids that is responsible for chain scission and subsequent deterioration of the mechanical properties of the polymer. In the present study we validate a new protocol based on Raman spectroscopy, which is suitable on assessing the structural degradation of polyethylene induced by oxidation. Following in vitro accelerated aging experiments, the oxidation index (01) of different commercially available HXLPEs, as calculated by infrared spectroscopy according to ASTM standard, has been univocally correlated to the most severe variation of crystalline phase (a,), as calculated by Raman spectroscopy. In each material, locations with equal values of 01 showed different degree of recrystallization induced by chain scission, confirming that infrared spectroscopy might overestimate the effective mechanical degradation of the polymer. In addition, as compared to the standards based on infrared spectroscopy, this new method of assessing oxidation enables to investigate the degradation occurring on the original surface of HXLPE components, due to the nondestructive nature of Raman spectroscopy and its high spatial resolution.Statement of SignificanceIn the present study we validate a new protocol based on Raman spectroscopy, which is suitable on assessing the structural degradation of polyethylene induced by oxidation. In fact, the standard methodology to investigate the oxidation in polyethylene relies on the use of infrared spectroscopy, which is capable of detecting the presence of oxidized species containing carbonyl group, the main products of oxidation in polyolefins. If from one hand this technique enables quantitative analysis of oxidation, on the other hand it is not capable of discriminating the fraction of species with carbonyl groups responsible for the chain scission. In fact, esters, ketones and carboxyl acids are products of oxidation with carbonyl groups commonly formed on polyethylene at the end of the oxidative cascade initiated by the presence of free radicals, but only the latter are responsible for the chain scission and the subsequent deterioration of the mechanical properties. The oxidation index as obtained according to the ASTM standards is not univocally correlated to a certain degree of mechanical deterioration, but, in simple words, two retrievals with the same amount of carbonyl groups might have had different degradation of the mechanical properties. Recrystallization is a direct consequence of the reduction of molecular weight that occurs after chain scission. Raman spectroscopy (RS) is a viable non-destructive method to assess the fraction of crystalline phase in polyethylene and, due to its high spatial resolution, is perfectly suitable to analyze the microstructural modification at the mesoscopic scale, where the effects of oxidation manifest themselves. The aim of the present paper is twofold: i) to compare the microstructural modifications caused by in vitro oxidation on 5 different types of polyethylene currently available on the market of joint replacements; ii) to establish a protocol based on the comparative analysis of IR and RS results to obtain a phenomenological correlation capable to judge the mechanical deterioration of the material induced by the oxidative degradation. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.