Fittipaldi Mauro, Grace Landon R
Department of Mechanical and Aerospace Engineering, University of Miami, Coral Gables, FL, USA.
Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC, USA.
J Mech Behav Biomed Mater. 2017 Apr;68:80-87. doi: 10.1016/j.jmbbm.2017.01.031. Epub 2017 Jan 24.
The thermoplastic elastomer Poly(Styrene-block-Isobutylene-block-Styrene) (SIBS) is highly biocompatible, which has led to its use in several commercially-available implants. However, lipid-induced degradation has been previously identified as a primary cause of failure in long-term SIBS implants subject to mechanical loading. Thus, understanding the mechanisms and extent of lipid-induced damage and the role of styrene-isobutylene ratio and molecular weight is critical to improving longevity of SIBS-based implants in order to fully exploit the biocompatibility advantages. Samples of four different SIBS formulations were fabricated via compression molding, immersed to lipid saturation contents from 5 to 80% by weight, and tested in uniaxial tension, stress relaxation, and dynamic creep modes. Degradation mechanisms were investigated via infrared spectroscopy, chromatography, and microscopy. No evidence of lipid-induced chemical interactions or chain scissoring was observed. However, a decrease in tensile strength, loss of dynamic creep performance and faster relaxation with increasing lipid content is attributed to strong internal straining. The magnitude of these losses is inversely proportional to both molecular weight and styrene content, suggesting that selection of these variables during the design phase should be based not only on the mechanical requirements of the application, but the expected degree of lipid exposure.
热塑性弹性体聚（苯乙烯-嵌段-异丁烯-嵌段-苯乙烯）（SIBS）具有高度的生物相容性，这使其被用于多种市售植入物中。然而，脂质诱导的降解先前已被确定为长期承受机械负荷的SIBS植入物失效的主要原因。因此，了解脂质诱导损伤的机制和程度以及苯乙烯-异丁烯比例和分子量的作用对于提高基于SIBS的植入物的使用寿命至关重要，以便充分利用其生物相容性优势。通过压缩成型制备了四种不同SIBS配方的样品，将其浸入重量比为5%至80%的脂质饱和溶液中，并在单轴拉伸、应力松弛和动态蠕变模式下进行测试。通过红外光谱、色谱和显微镜研究降解机制。未观察到脂质诱导的化学相互作用或链断裂的证据。然而，随着脂质含量的增加，拉伸强度降低、动态蠕变性能丧失以及松弛加快归因于强烈的内部应变。这些损失的程度与分子量和苯乙烯含量成反比，这表明在设计阶段选择这些变量时不仅应基于应用的机械要求，还应基于预期的脂质暴露程度。
