Understanding Sterilization Techniques for Polyurethanes in Biomedical Applications

The medical device industry has established guidelines and procedures in collaboration with the Association for the Advancement of Medical Instrumentation (AAMI) and the European Committee for Standardization (CEN). These efforts aim for global harmonization between European and American standards to ensure the safe use of materials like polyurethanes in medical applications. Sterilization is a critical process in this context, as it eliminates contaminants and ensures the safety of medical devices.

One common sterilization method is steam heat sterilization, which, despite its efficiency, poses potential concerns. Research indicates that under normal conditions, this technique does not produce harmful compounds such as 2,4-toluenediamine (MDA). However, it has been suggested that this process can lead to hydrolysis in some polyurethane materials, particularly those susceptible to moisture and heat. This means that careful consideration must be given to the types of polyurethanes being sterilized using steam heat.

Autoclaving has proven to be effective for thermoset polyurethanes, which are more resilient to the harsh conditions of heat, moisture, and pressure. In contrast, polyester-urethanes are advised against autoclaving due to their vulnerability to hydrolysis. Ethylene oxide (EO) sterilization stands out as a favorable method, especially for polyurethane materials, since it results in minimal toxic byproducts compared to other techniques like autoclaving and gamma-ray sterilization. However, manufacturers must ensure that residual EO levels in the products remain within safe limits.

Gamma-ray sterilization is widely used for various biomedical materials, including polyethylenes and polystyrenes. Despite its prevalence, this technique can lead to detrimental effects on polyurethane properties, such as chain scission and crosslinking, resulting in compromised mechanical integrity. Research has shown that gamma-ray sterilization can produce more MDA than steam sterilization, posing additional concerns for manufacturers and healthcare providers.

Several commercial polyurethanes are employed in biomedical applications, each requiring specific processing and sterilization methods. For example, products like Angioflex® and Cardiothane® are designed for particular uses, including artificial hearts and blood conduits, and must be sterilized appropriately to maintain their functionality and safety. Understanding these materials and their sterilization requirements is essential for ensuring effective and safe medical devices.