Millon L E, Wan W K
Graduate Program in Biomedical Engineering, University of Western Ontario, London, Ontario N6A 5B9, Canada.
J Biomed Mater Res B Appl Biomater. 2006 Nov;79(2):245-53. doi: 10.1002/jbm.b.30535.
Finding materials suitable for soft tissue replacement is an important aspect for medical devices design and fabrication. There is a need to develop a material that will not only display similar mechanical properties as the tissue it is replacing, but also shows improved life span, biocompatibility, nonthrombogenic, and low degree of calcification. Polyvinyl alcohol (PVA) is a hydrophilic biocompatible polymer with various characteristics desired for biomedical applications. PVA can be transformed into a solid hydrogel with good mechanical properties by physical crosslinking, using freeze-thaw cycles. Hydrophilic bacterial cellulose (BC) fibers of an average diameter of 50 nm are produced by the bacterium Acetobacter xylinum, using a fermentation process. They are used in combination with PVA to form biocompatible nanocomposites. The resulting nanocomposites possess a broad range of mechanical properties and can be made with mechanical properties similar to that of cardiovascular tissues, such as aorta and heart valve leaflets. The stress-strain properties for porcine aorta are matched by at least one type of PVA-BC nanocomposite in both the circumferential and the axial tissue directions. A PVA-BC nanocomposite with similar properties as heart valve tissue is also developed. Relaxation properties of all samples, which are important for cardiovascular applications, were also studied and found to relax at a faster rate and to a lower residual stress than the tissues they might replace. The new PVA-BC composite is a promising material for cardiovascular soft tissue replacement applications.
寻找适合软组织替代的材料是医疗器械设计与制造的一个重要方面。需要开发一种材料，它不仅要展现出与被替代组织相似的机械性能，还要具有更长的使用寿命、更好的生物相容性、抗血栓形成性以及低钙化程度。聚乙烯醇（PVA）是一种亲水性生物相容性聚合物，具有生物医学应用所需的各种特性。通过使用冻融循环进行物理交联，PVA可以转化为具有良好机械性能的固体水凝胶。平均直径为50纳米的亲水性细菌纤维素（BC）纤维由木醋杆菌通过发酵过程产生。它们与PVA结合使用以形成生物相容性纳米复合材料。所得的纳米复合材料具有广泛的机械性能，并且可以制成与心血管组织（如主动脉和心脏瓣膜小叶）相似的机械性能。在圆周和轴向组织方向上，至少有一种PVA - BC纳米复合材料能够匹配猪主动脉的应力 - 应变特性。还开发了一种与心脏瓣膜组织具有相似性能的PVA - BC纳米复合材料。对所有样品的松弛特性（这对心血管应用很重要）也进行了研究，发现它们比可能被其替代的组织松弛速度更快且残余应力更低。新型PVA - BC复合材料是用于心血管软组织替代应用的一种很有前景的材料。
