School of Materials Science and Engineering, Nanyang Technological University, Singapore.
J Biomed Mater Res B Appl Biomater. 2012 Apr;100(3):693-9. doi: 10.1002/jbm.b.32501. Epub 2011 Nov 28.
We report on the testing of materials for a fully degradable tracheal stent. Such a stent has several advantages over currently used permanent stents made of metal or silicone polymers. However, the mode of degradation in the trachea is expected to be different from a fully submerged device, because of the uniqueness of the tracheal environment. A physical model was developed to allow an in-depth study of degradation of bioabsorbable polymers exposed to two differing media; namely 70 wt % water (gel) on one side and humidified air on the other, simulating conditions in a tracheal passage. Longitudinal microtome slices were obtained from both polymer surfaces and degradation kinetics data were derived from size exclusion chromatography. On the basis of the data obtained, it is observed that well-studied bulk-degrading polymers might show surface-eroding properties in such an environment. Generally, hydrophobic polymers retard the formation of a water concentration gradient and exhibit bulk-degradation kinetics. However, addition of specific plasticizers can influence the water uptake gradient, and force the polymer towards a pseudo "surface-eroding" behavior. In vivo studies in a rabbit model of degradable stents made from a selected polymer, demonstrate the feasibility of a fully bioabsorbable tracheal stent. This study aims to improve understanding of degradation of polymers under heterogeneous environments.
我们报告了一种完全可降解气管支架材料的测试结果。与目前使用的金属或硅酮聚合物制成的永久性支架相比，这种支架有几个优点。然而，由于气管环境的独特性，预计在气管中降解的方式将与完全浸没的装置不同。我们开发了一种物理模型，以允许深入研究暴露于两种不同介质的可生物吸收聚合物的降解；即在一侧为 70wt%的水（凝胶），另一侧为加湿空气，模拟气管通道中的条件。从两种聚合物表面获得了纵向切片，并从尺寸排阻色谱法中得出了降解动力学数据。根据获得的数据，观察到在这种环境下，经过充分研究的整体降解聚合物可能表现出表面侵蚀特性。一般来说，疏水性聚合物会阻碍水浓度梯度的形成，并表现出整体降解动力学。然而，添加特定的增塑剂可以影响水吸收梯度，并迫使聚合物表现出一种假的“表面侵蚀”行为。在一种选定聚合物制成的可降解支架的兔模型体内研究中，证明了完全可生物吸收的气管支架的可行性。本研究旨在提高对聚合物在非均相环境下降解的理解。
