Plasma sterilization eliminates viable microorganisms such as viruses, bacteria, and fungi, as well as their spores. Learn more about sterilization and disinfection with plasma now.
Plasma sterilization explained simply – Definition
Plasma sterilization is an innovative, fast, and highly effective low-temperature process (45 °C to 60 °C) for the residue-free elimination of germs and pathogenic microorganisms. It is typically used in pharmaceutical and medical fields and frequently in the packaging industry.
Advantages
The low-temperature process offers significant advantages—such as efficiency, gentleness on materials, sustainability, and workplace safety—over conventional sterilization methods such as steam (+100 °C) or ethylene oxide gas (toxic and leaves residues).
Due in particular to its thermolabile properties, which are beneficial for heat-sensitive instruments, dry plasma sterilization is suitable for materials sensitive to heat and moisture. These include, among others, surgical materials, plastics, dental instruments, cables, and aerospace materials.
Disadvantages
Plasma sterilization has fewer disadvantages and more limitations. For example, the items being treated must be completely dry and, when using low-pressure plasma, must also be vacuum-tight and plasma-resistant. Because the plasma treatment takes place in a vacuum chamber, even objects with complex geometries or cavities can be sterilized effectively—something that is not always possible without a reaction vessel.
plasma technology’s approach: Our plasma systems therefore use only low-pressure plasma for sterilization. This ensures efficient processing times, and thanks to the high durability of our products, our solutions are both efficient and cost-effective.
Applications for Materials and Products
Suitable products and materials for plasma sterilization or disinfection. Which products or materials can be disinfected or sterilized in low-pressure plasma?
Materials
In addition to various metals, polymers (plastics)—such as thermoplastics, thermosets, elastomers, TPU, and, in particular, silicones—can also be cleaned, disinfected, and sterilized using plasma. Glass, ceramics, and various textiles and membranes are also suitable for plasma sterilization and plasma disinfection.
In general, materials must be plasma- or vacuum-resistant in order to undergo plasma treatment. Materials that cause significant disruption to the vacuum or plasma due to heavy outgassing are therefore not suitable for treatment in low-pressure plasma.
Products
Typical products suitable for disinfection or sterilization in low-pressure plasma include those from the pharmaceutical, medical, and dental sectors, as well as the packaging industry. For low-pressure plasma sterilization, the products must be able to be placed inside the plasma chambers.
Fixed components, such as hospital interiors, cannot be treated with low-pressure plasma. Additionally, the plasma cannot reach products that are already packaged. In this case, the plasma sterilizes only the packaging, not the product itself.
Examples of products that can be successfully disinfected and sterilized in low-pressure plasma:
- Respiratory masks
- Safety goggles
- Surgical instruments
- Dental instruments
- Catheters and prostheses
- Endoscopes (thermolabile)
- PE, PP, and blister packaging
Even FFP3 respirators and other protective equipment for hospital staff, which are normally intended for single use, can be reprocessed for further use through plasma disinfection.
Process and Mechanism
Gas plasma sterilization is a gentle, dry, low-pressure process that oxidizes and completely destroys the cellular components of viable microorganisms. Since it is typically performed at temperatures between 37 °C and 60 °C, it is ideally suited for heat-sensitive materials.
Plasma Sterilization Process
Plasma has been proven to damage or inactivate all components of pathogens, such as bacteria, viruses, virions, prions, and fungi and their spores. This destroys, among other things, their cell walls, viral or spore coats, cell membranes, and the pathogens’ DNA genetic material. Furthermore, plasma removes contaminants and toxins from surfaces.
In a low-pressure process, the items to be sterilized (cleaned and dried) are placed in a sterilization chamber. When using low-pressure plasma, the chamber is evacuated to create a vacuum, and a process gas is introduced.
Due to the high penetrability of low-pressure plasma, even the smallest cavities and crevices are reached during plasma disinfection or sterilization. Depending on the process gas used and the selected treatment intensity and duration in the plasma atmosphere, products are both disinfected and sterilized.
How Plasma Sterilization Works
The scientifically proven sterilizing effect of plasma is the result of several factors.
The factors and how they work in detail:
High reactivity of the particles contained in the plasma
– The various reactive species contained in the plasma damage the organic molecules of living organisms, such as bacteria.
– Bacteria are killed by the oxides present in the plasma.
UV radiation generated in low-pressure plasma
– Ultraviolet radiation is a powerful disinfectant and damages the genetic material of pathogens, i.e., their DNA molecules.
– UV radiation affects living cells, such as bacteria, as well as viruses, which lack their own metabolism.
– Viruses are inactivated by the UV radiation present in the plasma.
– Bacteria are killed by the UV radiation present in the plasma.
High kinetic energy of ions and electrons
– The plasma particles strike the surfaces of the products at high speed, mechanically dislodging existing contaminants and pathogens (sputtering effects).
– Regardless of the nature of the particles—whether living or not—they can be mechanically dislodged, transferred into the gas phase, and removed from the treatment chamber via constant gas transport.
– The charged particles destroy bonds in the cell membranes and thus also penetrate the viral envelopes of enveloped viruses (for information: The SARS-CoV-2 virus is an enveloped virus).
The fine vacuum present in the low-pressure plasma
– The fine vacuum and the temperature increase upon contact with the high-energy plasma species cause the organisms of the pathogens to dry out.
Plasma Disinfection
Plasma disinfection reduces the number of disease-causing microorganisms so that an object no longer poses a risk of infection. These are methods for the targeted, but not complete, killing and inactivation of disease-causing (pathogenic) microorganisms. Disinfected objects are therefore not 100% germ-free, but rather have a reduced or low microbial load. Effective disinfection achieves a KRINKO guideline of approximately 84 to 99.9%. Depending on the process gas used and the selected treatment intensity and duration in the plasma atmosphere, products are both disinfected and sterilized.
Difference from Plasma Cleaning
Plasma cleaning generally refers to the removal of unwanted contaminants and microorganisms without killing or inactivating the latter. In medical settings, cleaning can be performed, for example, using cleaning agents, wipes, or vacuum cleaners.
In the context of plasma, the mechanical removal of microorganisms through sputtering effects corresponds to simple cleaning. Simple cleaning achieves a germ reduction of approximately 50–80%. Plasma disinfection therefore achieves a significantly higher germ reduction than plasma cleaning.
Difference from Plasma Sterilization
The key difference between plasma disinfection and plasma sterilization lies in the (percentage) reduction in the microbial count, which is significantly reduced by disinfection (84 to 99.9%) and completely eliminated without residue by sterilization (100%). Sterile products are therefore free of viable microorganisms, such as bacteria, fungi, or spores. Prions, viruses, and virions must also be inactivated.
Plasma disinfection can be applied to living tissue, e.g., for wound treatment with cold plasma (below 40 °C), and performed on-site.
Plasma sterilization is typically performed in an optimized low-pressure plasma system with appropriate processing times and process gases.
Suitable Plasma Systems and Process Gases
The selection of the appropriate plasma system and process gas depends primarily on the product to be treated. Product quantities, the scheduled timing of disinfection or sterilization, and the desired outcome must also be taken into account.
Suitable plasma systems for sterilization with low-pressure plasma:
If a sterilization process is to be integrated into production, large-volume production systems are the ideal choice. Production systems are adapted to the specific requirements of the products to be sterilized and tailored to existing manufacturing processes. The plasma systems can also be equipped with a pass-through function.
Suitable low-pressure plasma systems for plasma disinfection:
For more mobile on-site use, such as disinfection after the first use of smaller products, small laboratory systems are certainly better suited.
Suitable process gases include various noble gases as well as hydrogen, nitrogen, and oxygen. Mixtures of different gases are also possible. The selection of the process gas depends on the product to be sterilized or disinfected. However, the desired effect of the plasma process is also a factor in the selection.