Zdrahala R J, Zdrahala I J
R&I Consulting International, Eden Prairie, MN 55346, USA.
J Biomater Appl. 1999 Jul;14(1):67-90. doi: 10.1177/088532829901400104.
Polyurethanes, having extensive structure/property diversity, are one of the most bio- and blood-compatible materials known today. These materials played a major role in the development of many medical devices ranging from catheters to total artificial heart. Properties such as durability, elasticity, elastomer-like character, fatigue resistance, compliance, and acceptance or tolerance in the body during the healing, became often associated with polyurethanes. Furthermore, propensity for bulk and surface modification via hydrophilic/hydrophobic balance or by attachments of biologically active species such as anticoagulants or biorecognizable groups are possible via chemical groups typical for polyurethane structure. These modifications are designed to mediate and enhance the acceptance and healing of the device or implant. Many innovative processing technologies are used to fabricate functional devices, feeling and often behaving like natural tissue. The hydrolytically unstable polyester polyurethanes were replaced by more resistant but oxidation-sensitive polyether polyols based polyurethanes and their clones containing silicone and other modifying polymeric intermediates. Chronic in vivo instability, however, observed on prolonged implantation, became a major roadblock for many applications. Presently, utilization of more oxidation resistant polycarbonate polyols as soft segments, in combination with antioxidants such as Vitamin E, offer materials which can endure in the body for several years. The applications cover cardiovascular devices, artificial organs, tissue replacement and augmentation, performance enhancing coatings and many others. In situ polymerized, cross-linked systems could extend this biodurability even further. The future will expand this field by revisiting chemically-controlled biodegradation, in combination with a mini-version of RIM technology and minimally invasive surgical procedures, to form, in vivo, a scaffold, by delivery of reacting materials to the specific site in the body and polymerizing the mass in situ. This scaffold will provide anchor for tissue regeneration via cell attachment, proliferation, control of inflammation, and healing.
聚氨酯具有广泛的结构/性能多样性，是当今已知的生物相容性和血液相容性最强的材料之一。这些材料在从导管到全人工心脏等众多医疗设备的发展中发挥了重要作用。诸如耐用性、弹性、类弹性体特性、抗疲劳性、顺应性以及在愈合过程中身体对其的接受或耐受性等特性，常常与聚氨酯相关联。此外，通过亲水性/疏水性平衡或通过连接生物活性物质（如抗凝血剂或生物可识别基团）对本体和表面进行改性的倾向，可通过聚氨酯结构特有的化学基团来实现。这些改性旨在调节和增强设备或植入物的接受度和愈合能力。许多创新的加工技术被用于制造功能性设备，这些设备的感觉和行为常常类似于天然组织。水解不稳定的聚酯型聚氨酯已被更具耐受性但对氧化敏感的聚醚多元醇型聚氨酯及其含有硅氧烷和其他改性聚合物中间体的同类产品所取代。然而，在长期植入时观察到的慢性体内不稳定性，成为了许多应用的主要障碍。目前，使用更具抗氧化性的聚碳酸酯多元醇作为软段，并与维生素E等抗氧化剂结合，可提供能在体内耐受数年的材料。其应用涵盖心血管设备、人工器官、组织替代与增强、性能增强涂层等诸多领域。原位聚合的交联体系甚至可以进一步提高这种生物耐久性。未来，通过重新审视化学控制的生物降解，并结合微型反应注射成型技术和微创手术程序，将反应材料输送到身体的特定部位并在原位聚合形成支架，这将拓展该领域。这种支架将通过细胞附着、增殖、炎症控制和愈合为组织再生提供支撑。
