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Pre-Sterilized NALGENE Labware
Ethylene Oxide
Gamma Irradiation
Other Testing

How is the sterility of NALGENE Labware assured?

Some NALGENE labware is sterilized and tested after assembly, and sterility is guaranteed as long as the packaging is intact. Two methods of sterilization are used -- ethylene oxide gas and gamma irradiation. Although our disposable filtration products are not classified as medical devices, they are sterilized following Good Manufacturing Practices of the United States FDA Medical Device Act of 1976. American Association of Medical Instrumentation (AMMI) recommended practices are used as a guideline for our sterilization methods.

Indicator dots used on NALGENE products undergo an irreversible color change upon sterilization and are specific for either ethylene oxide gas (EtO) or gamma irradiation. Purple EtO dots turn green when products have been properly processed. Yellow gamma dots turn red when products have been properly exposed.
Ethylene Oxide
Ethylene oxide (EtO) is used for sterilization where low temperature and pressure are necessary (the material to be sterilized cannot be autoclaved). The labware is exposed to EtO in chambers where temperature, humidity, and pressure are carefully controlled and monitored. NNI uses three methods to assess the outcome of the EtO procedure. External color indicators on the packaging demonstrate exposure to the gas but not sterility. Biological indicators are used to evaluate sterility. These indicators are resistant strains of bacterial spores, usually Bacillus subtillis var. niger, whose failure to grow demonstrates the effectiveness of the EtO cycle. Sterility testing may be performed on filterware after the sterilization process. As with biological indicators, the criterion for confirming sterility is the absence of microbial growth.
After EtO sterilization, the labware is quarantined until all test results are known. This quarantine period lasts from 7 to 14 days and assures adequate time for the outgassing of EtO and possible residues. NALGENE labware is routinely evaluated for the presence of these residues, and the levels found fall well below the FDA recommended limits for implanted medical devices.
NALGENE labware sterilized by EtO includes sterilization filter units, analytical filter units, and filter funnels.
Gamma Irradiation
During this procedure, the labware is exposed to high energy, ionizing gamma radiation from a Cobalt 60 source at room temperature. This process is indicated where there must be an absolute assurance that no potentially toxic residue, however minute, may be present to affect the experimental procedure. Product sterility is achieved by an accumulated absorbed radiation dosage measured in megarads (Mrads). Dosage levels are selected by a process verification dose experiment, which includes bioburden determination and sterility testing. The sterility of the product is assured by dosimetric release, which confirms that the specified minimum dose has been delivered to the product.
NALGENE labware sterilized by gamma irradiation includes all of our tissue culture filter units, our filter unit receivers and PETG bottles and carboys.
Other Testing

All NALGENE sterile labware products undergo testing for:
Bioburden
Pyrogens
Cytotoxicity(^1)

NALGENE filtration products are also subjected to several other tests, regardless of the type of sterilization they undergo. These include:
Membrane retention/unit integrity
Membrane thickness
Membrane extractables
Bubble point

Details on these tests are available from NNI Technical Service. Certification of sterility and compliance with specifications will be supplied upon written request. Write to Quality Assurance Department, NNI, Box 20365, Rochester, New York 14602-0365 USA. Or email us at nnitech@nalgenunc.com

(^1) All materials (including plastic housings and caps) used in our tissue culture units are tested and shown to be noncytotoxic, using both mouse fibroblast L929 cells and the more sensitive human diploid lung cell line WI-38. Guess, W.L., Rosenbluth, S.A., Schmidt, B., and Autian, J., Agar diffusion method for toxicity screening of plastics on cultured cell monolayers. J. Pharm. Sci. 54:1, p 1545-7, 1965.
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