Sterilization VS Sanitization
Background on Medical Device Sterilization
The sterilization of medical devices is a vital process to help prevent serious infections. Center for Devices and Radiological Health(CDRH) remains committed to encouraging novel ways to sterilize medical devices while reducing adverse impacts on the environment and public health and to developing solutions that avert potential shortages of devices that the American public relies upon.
The most commonly used method in the U.S. to sterilize medical devices is ethylene oxide (EtO), and it is widely used by medical device manufacturers and contract sterilizers worldwide. More than 20 billion devices sold in the U.S. every year are sterilized with EtO, accounting for approximately 50% of devices that require sterilization. While some innovations appear promising, other methods of sterilization cannot currently replace the use of EtO for many devices.
Sanitization vs Sterilization
It is important when going through the device gambit to understand the differences and nuances in terminology. In the end, that’s what medical devices are: a lot of nuances.
Sanitizing should not be confused with sterilizing.
Understanding the difference could mean the difference between a lengthier and potentially unnecessary FDA regulation path and a much shorter, less involved approval process.
While sanitizing reduces microorganisms to a safe level, sterilizing removes all microorganisms from an item. Sterilizing is not often performed in a commercial kitchen environment, but is used in places like hospital operating rooms.
FDA regulates liquid chemical sterilants and high-level disinfectants intended to process critical and semicritical devices. The FDA has published recommendations on the types of test methods that manufacturers should submit to FDA for 510[k] clearance for such agents.
We’ve included the link to their website for more clarity.
Understanding Types of Sterilization
Sterilization processes are complex, multiphasic, dependent on surface properties and geometries. They typically aren’t fun to perform and they’re not really enjoyable to either the person performing them or the bacteria that they’re killing. Given the growing complexity of medical devices, modeling remains challenging and microbiology tests cannot be avoided in many instances and from my perspective often encouraged because it can catch a lot of instances that otherwise would be assumed to be edge cases in medical device design of experiments (DoE).
The FDA recognizes several of these methods of sterilization. The innovation within the engineering, manufacturing and medical fields is ever evolving. New methods of sterilization are always emerging. This is not made to be an ever exhausting Bible, but a reference document that could help you on your journey to understanding the greater context and provide a brief breakdown of a few of the methods they currently recognize.
Steam Sterilization
Also known as autoclaving, this method uses moist heat to destroy microorganisms. Items are put in a chamber, which is filled with saturated steam under pressure. It's considered the least expensive and most reliable method for instruments that must be steam-permeable and heat-resistant.
If using this method, it is important to realize that the heat and pressure tend to be extreme for many devices which can cause issues if the devices were included with things like glue that were not made to handle pressure and heat at the same time.
Ethylene Oxide (EtO) Sterilization
A sterilization option for items that can't be processed using steam. Involves exposure to ethylene oxide gas, which requires care. EtO can be a respiratory irritant and is a known carcinogen. Utilizing Ethylene Oxide requires aeration time post-sterilization due to toxic residues.
Vaporized H2O2 and Plasma Gas Sterilization
A popular method of low-temperature sterilization where instruments are introduced to vaporized H2O2. Usually utilized on plastic, silicone, rubber, or with complex geometries. This method can be expensive and is not widely compatible with different metals, coating, and cellulose based materials.
A similar, but less common method is the use of hydrogen peroxide plasma in a chamber to sterilize equipment. After a vacuum is achieved in the chamber and the H2O2 vapor is injected, an electromagnetic field is applied, turning the vapor into ionized gas- or plasma. The free radicals created in the wake of this process kills microorganisms. The drawbacks of this processes are very similar, if only this process takes a much smaller load. It is also more costly than just the vaporized H2O2.
A key take away if you’re doing any engineering within this realm is if you are using anodization, you’re not going to have a fun time. Anodization does not handle this type of sterilization well and fading if not complete a racing of the anodization often occurs which we will cover in a later article.
Ionizing Radiation
A widely used industrial sterilization method, especially for pre-packaged, single-use medical products. This method uses high-energy radiation, such as: Gamma Rays, Electron Beam (E-beam), X-rays. This process damages the DNA of bacteria and other microorganisms and eradicates them. Misappropriating dosages of radiation could cause failure to sterilize the product. This could also cause damage or deterioration of goods undergoing sterilization.
Liquid Chemicals Sterilization
Also known as liquid sterilants or high-level disinfectants, uses extremely strong chemical agents to kill microorganisms. Some common chemical agents used: Glutaraldehyde, Ortho-phthalaldehyde (OPA), Peracetic acid, Hydrogen peroxide (liquid form). This process is normally utilized with devices that can’t withstand steam or gas sterilizing treatments. Sterilizing instruments this way can be time consuming and isn’t a terminal sterilization solution. Liquid sterilants are toxic and can cause eye, lung, and skin irritation.
This process can also be used for sterilization of additional items that come initially packed with the bags from factories, which is common and/or could be used intermittently between heavier, sanitization methods, depending on the requirements of the facility and the utilization of the device.
Filtration Sterilization
Unlike the aforementioned sterilization treatments, filtration doesn’t sterilize by killing microorganisms. This process physically removes them; This is accomplished by permeating them through a filter with minute pores. Something to the size of 0.22 microns, which removes bacteria, and in some cases viruses. While this process has miniscule safety hazards, this also means that again, this doesn’t kill any microorganisms- just removes them.
This covers a wide net of sterilization tactics utilized industry wide. Each method has its own risks and rewards, much like anything else. Of course, if sterilization is something pivotal to the development of your product or device- do your own research and find the right method for you.
Much like understanding the different tracks for how you will be going through the FDA. It is super imperative and important the beginning of any project to work with your engineering team or your partners to understand the sterilization process because it affects not only the materials but the overall build of the unit a wrong application for sterilization or sanitization could have huge impact later on after products are built and being tested.
We hope this was helpful and make sure to stay tuned for the next one.