Is Parylene Coating Biocompatible?

Parylene is one of the most biocompatible conformal coatings currently available. Its chemical properties make it a natural for use in medical and biological applications. In addition, some of its general benefits also make it particularly valuable in healthcare applications. Finally, Parylene also holds a stringent USP Class VI biocompatibility certification.

Parylene’s Chemistry and Capabilities

One of Parylene’s key benefits for biological applications is that it is chemically inert. Just about anything that it would encounter inside a body would have no impact on it. Acids, bases, salts and organic chemicals have essentially no ability to break it down.

It is also hydrophobic, making it impervious to water. This means that it is a powerful tool for sealing items against bodily fluids.

The Parylene coating film is colorless and odorless, eliminating an additional source of irritation. Furthermore, because it requires no catalysts or initiators to be vaporized, deposited or cured, it also has no impurities that could compromise its unique benefits.

Physical Characteristics of Parylene

More than being chemically biocompatible, Parylene is also a powerful tool based on its physical attributes. From its strength to its thermal capabilities that are optimized for biological applications, it is structured for implantability.

Parylene’s unique vapor-based method of deposition means that it provides the best possible conformal coating. It coats anything that air can touch. This means that it generates a coating not just on top of components but also under them. It can even coat inside an item if it has even a microscopic opening to gas molecules (i.e., air). While this can be challenging for some applications, it is a desirable capability in biological settings. Adding to its desirability, Parylene coats evenly and without any pinholes.

Typically, discussions of Parylene’s thermal endurance focus on its ability to withstand temperatures of up to 80°C for continuous periods. However, biological applications typically involve contact with lower temperatures. Parylene can also withstand high pressures and even radioactivity, making it an excellent coating for items that need to go through medical-grade sterilization procedures.

Parylene forms a strong coating that is also flexible. This means that in some applications — like stents — it can add a small degree of needed reinforcement to the component. In addition, it also forms an extremely smooth coating. In fact, it has lubricity that is roughly comparable to that of PTFE. This means that Parylene coated items are likely to be easier to insert and to cause less irritation and discomfort while they are implanted.

The USP Class VI Standard

Parylene is not just biocompatible because of its structure and chemistry. It is also biocompatible because The United States Pharmacopeia (USP) has certified it to be. Furthermore, it meets the USP’s highest standards for biocompatibility — the Class VI standard.

The USP Class VI standard uses three broad types of testing to determine if a given plastic is truly biocompatible. These tests include Intracutaneous Reactivity, Acute Systemic Toxicity and Implantation. 

Parylene has been through this stringent process and earned its USP Class VI certification. In addition, over a period of more than 40 years, it has proven its ability to withstand biological applications with excellent performance and results for the patients benefiting from Parylene-coated medical devices. SCS maintains FDA Drug and Device Master Files that may be referenced by FDA examiners on behalf of SCS coating service customers.

Over a period of decades, Parylene has proven itself to be an outstanding option for coating medical devices. From simple items like coated syringes all of the way up to coated stents, implantable devices and surgical equipment, Parylene saves lives and improves outcomes.