Overview of Sterilization Procedures
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A primary concern in the design of a sterile barrier system is the sterilization process. Key considerations dictated by the sterilization method include porosity requirements, material and device compatibility (either functional or cosmetic), and the handling logistics required before, during, and after sterilization, such as the type of overpackage (e.g., corrugated boxes and product carriers). The commonly used procedures are summarized below; however, the science of sterilization continues to evolve and the introduction of new materials will also dictate the impact of these considerations upon the design of the entire packaging system.
Gaseous and Chemical Processes—In general, these processes require porosity to allow gas permeation and to withstand moderately elevated temperatures. Safety concerns include outgassing of hazardous materials via the package in the event of gas retention or residuals if proper precautions are not taken. This may require aeration prior to safe handling.
Ethylene Oxide—Sterilization by alkalizing gas.
Peroxide—Sterilization by oxidizing gas.
Ozone—Sterilization by oxidizing gas.
Chlorine Dioxide—Sterilization by oxidation and other chemical-based biocidal actions.
Radiation and E-Beam Processes—These processes use electromagnetic radiation or accelerated particles such as electrons to destroy bonds within biological cells. These techniques require the package to allow passage of the radiation or particle stream while minimizing packaging material degradation.
Pulsed UV Light—Destruction of molecular bonds using UV radiation generally with 200–300–nm wavelength.
X-Ray and Gamma Irradiation—Destruction of DNA and other molecules through exposure to electromagnetic radiation at specific wavelengths from various sources.
Electron Beam—Ionization and bond dislocation through exposure to electron beams.
Steam and Heat Processes—As these processes deliver heat to achieve biocidal action, packaging materials used must be able to withstand significantly elevated temperatures.
Steam—Steam can be delivered in an autoclave under pressure or at atmospheric conditions. Steam sterilization requires sterile barrier system materials that allow direct contact of the steam with the device to be sterilized, and that do not degrade in high humidity.
Autoclave—This is suitable for applications where there is liquid inside the package and thus requires nonporous materials which also do not degrade in high humidity. At the elevated temperatures employed, the heated liquid becomes the sterilant.
Dry Heat—Because there is no moisture involved, this process requires packaging materials capable of tolerating long exposure times at elevated temperatures.