The Evolution of Polyurethanes in Biomedical Applications

In the mid-20th century, the quest for optimal biomaterials led researchers to explore the potential of polyurethanes for medical applications. Initially, polyester-urethanes gained attention for their possible use in heart valves, chambers, and aortic grafts. However, the early cardiovascular applications faced significant challenges due to the hydrolytic instability of these materials, leading to disappointing outcomes. This realization lumped all polyurethanes together as unsuitable for implants, reflecting a limited understanding of the diverse family of materials within this category.

The tide began to turn when polyether-urethanes—recognized for their superior hydrolytic stability—emerged as a more promising alternative. This shift rekindled interest in polyurethanes, allowing researchers to delve deeper into their properties and potential applications. The early misclassification of polyurethanes highlighted the importance of distinguishing between different subclasses, paving the way for advancements in biomaterials that could meet the rigorous demands of medical devices.

The introduction of Lycra® spandex by DuPont in 1954 marked a significant milestone in the journey of polyurethanes. Initially created as a high-performance alternative to natural rubber, Lycra® was later adapted for biomedical use in 1967. Its unique properties, such as durability and flexibility, made it an ideal candidate for components like cardiac assist pumps. This versatility showcased the potential of segmented polyether-urethane-ureas in medical applications, setting a foundation for future innovations.

The 1970s saw the development of specialized polyurethanes for medical use, most notably Avcothane-51™ and Biomer™. These materials were synthesized specifically for biomedical applications, offering key properties such as thromboresistance and biostability. Avcothane™ ultimately played a pivotal role in the first intra-aortic balloon pump (IAB), while Biomer™ was utilized in the groundbreaking "Jarvik Heart," the first artificial heart implanted in humans. These innovations not only demonstrated the capabilities of polyurethanes but also addressed critical gaps in cardiac assist device technology.

The momentum continued with the commercialization of Pellethane™ 2363 series in 1977, which became the first medical-grade thermoplastic polyether-urethane. Its application as the catheter for the Avco™ IAB underscored the growing acceptance of polyurethanes in implantable devices. Ongoing studies into the toxicity and in vivo stability of these materials further clarified their safety and efficacy, reinforcing their place in the biomedical landscape.

As research and development in biomaterials progress, polyurethanes are likely to remain at the forefront of medical device innovation. Their adaptability and evolving formulations continue to open new avenues for enhancing patient care through advanced medical technologies.