Why Noxilizer
Noxilizer enables terminal sterilization for products that cannot tolerate traditional methods
Terminal sterilization versus aseptic processing alone
Sterilization is an essential requirement for the pharmaceutical, biotech and medical device industries because even medical innovations manufactured and filled under aseptic conditions can introduce microbial risk to patients.
For some drug delivery devices, especially in ophthalmology, FDA, EMA, and USP <1211> all emphasize that terminal sterilization is preferred over aseptic processing due to its higher sterility assurance level (SAL of 10⁻⁶ vs. 10⁻³).
ASEPTIC PROCESSING ALONE:
Sterility assurance level (SAL) = 10-3 = Fewer than 1 non-sterile unit per 1000
TERMINAL STERILIZATION AFTER ASEPTIC PROCESSING:
Why other methods fails
Traditional terminal sterilization methods (i.e., ethylene oxide [EtO], gamma, heat) are designed for robustness and scale but often introduce compromise for prefilled syringes and biologic drug products:
High heat and radiation degrade proteins
High heat from EtO, steam, and VHP can lead to protein denaturation:
Ionizing radiation from x-ray and gamma can break the protein chains:
Pressure changes (due to vacuums) can force syringe plungers to move, allowing microbes and sterilant to contaminate the biologic drug products
HEADSPACE
Prefilled syringes have a small amount of gas-filled space between the product and stopper/plunger
PLUNGER MOVEMENT
When exposed to low pressure (vacuum), this air expands and then contracts when the pressure increases, forcing the plunger to move up and down
MICROBIAL PLUNGER VEILING
Veiling occurs when the plunger moves and traps microbes between the plunger and syringe wall, shielding them from sterilant
INGRESS
Plunger movement may pull sterilant into the drug itself and contaminate the biologic active ingredient
RESOURCE — TO LEARN MORE:
Terumo study finds that NO2 did not chemically alter protein in prefilled syringes, whereas EtO and VHP did
Fujiwara S, et al. J Pharm Sci. 2022 Jan;111(1):41-50. doi: 10.1016/j.xphs.2021.09.003. Epub 2021 Sep 6. PMID: 34499900.
Noxilizer’s proprietary terminal sterilization process
“The NO2 sterilization process is completed in a vacuum chamber and begins with evacuation of the air in the sterilization chamber. After evacuation, the sterilization chamber is filled with the sterilization process gases which consist of NO2 and humidified air. For most medical devices and drug delivery devices that can tolerate a deep vacuum” of 150 mbars, “the chamber is evacuated to a relatively low vacuum pressure (e.g., 20 mbar; see figure below).
Some drug delivery devices, such as prefilled syringes, are susceptible to piston” (plunger) “movement during the sterilization cycle, due to the influence of the evacuated pressure, which causes the gases in the prefilled syringe to expand. The movement of the syringe piston may allow for the contamination of the syringe contents with both microorganisms and sterilant
gas. To address this issue, a shallow-vacuum cycle has been developed. This type of
shallow-vacuum cycle uses a much higher minimum process pressure (e.g., about 500 mbar
minimum process pressure) compared to typical minimum process pressure levels used
with deep vacuum cycles.”
Excerpt from Ray N, et al. Drug Delivery Device Design and Compatibility with Nitrogen Dioxide Gas Sterilization. Pharmaceuticals (Basel). 2025 Dec 8;18(12):1869. doi: 10.3390/ph18121869. PMID: 41471358; PMCID: PMC12736310:
With the NO2 process, both deep vacuum and shallow-vacuum cycles have similar process stages. These stages are described below and illustrated in the figure below. The process stages are:
Evacuation
Humidity Addition
Relative Humidity (RH) is added to the chamber until the desired percentage is reached, typically between 40% RH and 80% RH.
NO2 Injection
Pressurization
NO2 Exposure Stage
Aerations
†ISO 14937:2009; Sterilization of Health Care Products—General Requirements for Characterization of a Sterilizing Agent and the Development, Validation and Routine Control of a Sterilization Process for Medical Devices. International Organization for Standardization: Geneva, Switzerland, 2009.
Graph of pressure (mbar) vs. time (minutes) for an example deep vacuum NO2 sterilization cycle.
Figure adapted from Ray N, et al. Pharmaceuticals (Basel). 2025;18(12):1869.
Mechanism of action
NO₂ sterilization works by damaging the DNA and RNA of microorganisms so extensively that they cannot survive or repair themselves. When NO₂ enters the sterilization chamber, it mixes with a small amount of humidity to form reactive nitrogen species, including dinitrogen trioxide (N₂O₃), a potent nitrosating agent. These reactive molecules penetrate spores and cells and break their DNA and RNA strands, preventing the organism from reproducing.
Laboratory studies show that NO₂ causes rapid, irreversible single‑strand DNA breaks (SSB), beginning within minutes. Even one of these breaks is enough to stop a cell or spore from completing mitosis or germination. As exposure continues, the damage accumulates into complete DNA degradation, leaving microorganisms with no ability to recover or repair themselves.
Rapid aeration — hours vs. days
Nitrogen dioxide’s low boiling point allows for rapid aeration.
NO2 does not permeate materials to the same degree as other methods, greatly reducing the overall cycle time of the sterilization process and eliminating the lengthy post-sterilization aeration. (Noxilizer has short overall cycle times of 6–12 hours.) This benefit applies to terminal sterilization using a batch process or high-level decontamination in isolators.
The rapid aeration process results in fewer residuals on product and packaging. Noxilizer’s sterilant residues are non-carcinogenic, non-cytotoxic and non-teratogenic. Sterilized batches can be handled and packaged/shipped immediately without any health risk concerns for employees.
Material compatibility
NO₂ is compatible with many materials
Don’t see a material on this list?
We would be happy to provide you with more information about material compatibility.
RESOURCE— TO LEARN MORE:
Drug delivery device design and compatibility with NO2 gas sterilization
Ray N, et al. Pharmaceuticals (Basel). 2025 Dec 8;18(12):1869. doi: 10.3390/ph18121869. PMID: 41471358; PMCID: PMC12736310.
Packaging compatibility
NO₂ is compatible with commonly-used sterile barrier packaging, including:
- Tyvek® pouches
- Tyvek® – Mylar® pouches
- Thermo Formed (PETG) with Tyvek® lids
Noxilizer’s process is not compatible with cellulosic materials such as paper and cardboard. Due to incompatibility of cellulosic materials, consideration needs to be given to labels and inserts that are included during sterilization. Those items can be added after sterilization as part of final packaging.
Why customers choose Noxilizer biological indicators.
Our rigorous characterization program helps customers:
- Increase confidence in cycle development and validation
- Reduce variability during qualification studies
- Support regulatory submissions with robust scientific data
- Improve process control and monitoring
- Accelerate sterilization program execution
Every spore batch & every BI lot are fully characterized, supporting validated, reproducible sterility
Biological indicators designed for confidence
When sterilization validation is critical, the quality and consistency of the biological indicator matter. At Noxilizer, we take a scientifically rigorous approach to biological indicator manufacturing by characterizing every spore production batch before application and every finished biological indicator lot after application to the carrier.
This dual-stage characterization provides exceptional lot-to-lot consistency, predictable resistance profiles, and greater confidence that the biological indicator accurately challenges the sterilization process.
A higher standard for biological indicators
Unlike conventional biological indicators that rely primarily on characterization of the initial spore crop, Noxilizer evaluates both the incoming spore population and the finished biological indicator. This approach ensures that the effects of manufacturing and spore application are understood and controlled, resulting in a more reliable challenge system for sterilization validation and routine monitoring.
Using ISO 18472-aligned resistometer methodologies, we evaluate critical performance characteristics including:
Designed specifically for NO2 sterilization
Noxilizer biological indicators utilize Geobacillus stearothermophilus spores with a population greater than 106 CFU on proprietary quartz carriers engineered for nitrogen dioxide sterilization applications.
Key features include:
- Characterization of every spore production batch
- Characterization of every finished biological indicator lot
- Fully characterized resistance profiles
- Lot-to-lot consistency verification
- 12-month shelf life
- Transport stability validation
- Up to 48-hour post-exposure hold time
- 42-hour reduced incubation capability
- Complete quality documentation and traceability
Proprietary, validated, resistometer-measured biological indicators (BI)
RESOURCE— TO LEARN MORE:
NO2 sterilization follows log-linear microbial inactivation kinetics using Geobacillus stearothermophilus biological indicators
Richards T, et al. PDA J Pharm Sci Technol. 2025 Aug 1;79(4):379-390. doi: 10.5731/pdajpst.2024.012997. PMID: 40523727.
RESOURCE— TO LEARN MORE:
Biological indicators and process challenge devices for nitrogen dioxide sterilization
Lisco D, et al. Biomed Instrum Technol. 2026;60(2):19-31. doi: 10.2345/0899-8205-60.2.19. Epub 2026 May 5. PMID: 42085597; PMCID: PMC13143232.
