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Five Common Misconceptions About Electron Beam Sterilization

Tue, 09/15/2009 - 11:25am
Electron beams are a source of ionizing radiation, similar to Gamma radiation, and have been successfully used for sterilization for pharmaceutical and medical device applications for decades. The mechanism of microbial disinfection is well understood and the development, validation and control of this type of technology are covered by ISO 11137 Sterilization of Healthcare Products by Radiation documentation. Electron beams differ from Gamma in that they do not depend on the decay of a radioactive isotope to generate the sterilizing energy. In an electron beam system, free electrons are accelerated with a voltage differential and directed towards a product.

While electron beam technology is well established, there are still common misconceptions within the pharmaceutical and medical device industry.

1. Electron beam devices are extremely large and require dedicated facilities
Traditional high voltage electron beam technology is quite large. Complex accelerator designs requiring active vacuum pumping systems and large power supplies have significantly limited the potential applications for electron beam sterilization. However, the past several years have seen radical advancements with the introduction of compact electron beam emitter technology that does not require the use of an external vacuum pumping system and utilizes compact, rack mountable power systems. Compact electron beams have opened up the potential to bring the technology directly to the manufacturing process.

2. Electron beams are exclusively for terminal sterilization
Traditional electron beam technology, based on high voltage (500keV to 10 MeV) accelerator designs, work similarly to Gamma irradiation. High energy electrons penetrate deeply into the material being treated, delivering energy throughout the depth of the product. Low energy (e.g. 80-150keV) electron beams deliver energy predominately to the surface. In addition to being more compact, low energy electron beams are more appropriate for surface sterilization or treatment of thin films. By concentrating energy to the surface, pharmaceutical and medical device manufacturers can sterilize packaging without affective the bulk material properties of the packaging or affecting a drug or device already in the package.

3. Electron beam sterilization is a slow process
While faster than Gamma irradiation, traditional electron beam sterilization does require residence time for products to accumulate sufficient energy exposure to ensure full sterilization. In contrast, since low energy electron beams concentrate energy to the surface, sterilizing levels of energy can be delivered at very high speeds. For most applications, sterilizing doses can be delivered with milliseconds of exposure time. With low energy electron beam technology, sterilization is not the rate limiting step of a packaging application.

4. Electron beam technology is complicated and requires a high level of operator expertise
While electron beams are a high tech product and recent advancements are the product of years of research and development, the technology is very simple to maintain and requires far fewer critical control points than heat or chemical-based sterilization methods. Since sterilization is dependant on electron dose delivery, and the dose delivered is solely dependant on line speed, voltage, and current - all of which can be digitally controlled and monitored - control of the sterilization process is extremely straightforward. This simplicity translates to longer validated filling campaigns and a more straightforward validation process.

5. Electron beam sterilization is only appropriate for a few niche applications (e.g. syringe tub sterilization)
While the first in-line applications for low energy electron beams have been sterile transfer of syringe tubs for isolator filling, there is growing interest in using the technology for direct sterilization of primary packaging components and for more high value sterile connection applications. The flexibility of compact electron beam technology opens up a new range of potential applications. In particular, the technology is well suited for applications requiring:
§ The highest levels of sterility assurance
§ High throughput line speeds
§ The need to protect pre-packaged product from effects of sterilization
- Josh Epstein, Director of Marketing, Advanced Electron Beams

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