Today's KNOWLEDGE Share:STERILIZATION METHODS

 Today's KNOWLEDGE Share:

STERILIZATION METHODS:

Plastics are used to manufacture a wide range of medical products, including those used as part of surgical and other invasive medical procedures. According to the Center for Disease Control, approximately 46.5 million of these procedures are performed annually. Each procedure presents a major risk for the introduction of pathogens: bacteria, fungi, parasites, and viruses. Because of this, sterilization and disinfection are important.

Sterilization describes a process that destroys or eliminates all forms of microbial life, including both pathogens and spores, by physical or chemical methods.

Disinfection describes a process that eliminates many or all pathogenic microorganisms, except bacterial spores, on inanimate objects.

Sterilization and disinfection methods include:

· Heat Sterilization: both hot air, and autoclaving (steam)

· Irradiation: both gamma and E-beam radiation

· Chemical Sterilization: both gaseous and liquid products

Each method has advantages and disadvantages based upon many factors including efficacy, equipment and operating costs, time required, and environmental concerns. A major issue with the use of sterilizing methods, is that they all can have a deleterious effect on plastics. Plastic materials can undergo molecular degradation and environmental stress cracking (ESC) when subject to sterilization or disinfection.

This has been illustrated over the last 10 years by the failures of plastic medical devices in contact with aggressive chemical disinfectants, such as those based on quaternary ammonium salts, glutaraldehyde, phenolics, alcohol, and chlorine compounds. The synergistic effects of these chemicals, together with molded-in and assembled-in stress, have produced a rash of failures.

The best way to minimize the chances of premature failure is to do upfront material compatibility testing. A good guideline for this testing is ASTM D543, “Standard Practice for Evaluating the Resistance of Plastics to Chemical Reagents” Practice A involves sterilization of unstressed plastic samples, followed by assessment of weight and dimensional changes, as well as mechanical property changes. This is useful for the assessment of chemical attack and molecular degradation. Practice B of the standard includes exposure of stressed plastic test specimens, followed by inspection for crack formation and testing for mechanical property changes.

This type of chemical compatibility testing should be done early in the product development cycle, before manufacturing tooling and methodologies have been finalized. This allows for material changes with minimal cost implications if incompatibility issues are identified.

Source:The Madison Group