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From: Food Quality & Safety magazine, June/July 2005

The N-Halamine Suit of Armor

Antimicrobial uniforms and gloves safeguard from worker contamination.

by Dr. Jeff Williams

As a result of highly publicized foodborne illness outbreaks, demand continues to increase for hygienic surfaces, capable of persistent antimicrobial action. There are many approaches to built-in antimicrobial technology, and some of these applications are timely and cost-effective to implement.

One such application targets a major contamination threat in the food industry today: Workers. What if the uniforms and gloves they wear - a single layer of protection - could also actively kill germs before they can ever be transmitted?

Fabrics, vinyl and many other surfaces treated with antimicrobial coatings can give organizations new ability to reduce the risk of many common and alarming contamination threats, including E. coli, Salmonella, Staphylococcus aureus and many other well-known bacteria commonly found in food preparation and food packaging facilities.

Today, innovative N-Halamine antimicrobial chemistries are coming to market, delivering biocidal speed, efficacy and longevity. These chemistries can be applied as a coating, delivering a renewable, durable and highly effective antimicrobial solution.

The N-Halamine approach harnesses the proven killing power of chlorine - commonly available in the form of household bleach - to prolong and localize its antimicrobial effects at the treated or coated surface, where bacteria, fungi, viruses and germs first make contact.

The key feature of N-Halamine treated uniforms and gloves is that the antimicrobial power can be renewed with bleach, as part of the normal laundering regime. This feature makes its antimicrobial properties highly effective for the life of the product, sustained and refreshed with each new laundering cycle.

For the food industry, this represents a major advantage to help reduce food contamination. An outbreak affects consumers' perception of the entire market for that product, as evidenced by the impact that E. Coli contamination had on hamburger sales after the widely publicized accounts of a few, but very serious, cases.

N Killing Power

N-Halamine compounds have a unique molecular structure that binds chlorine to treated surfaces to provide extended antimicrobial properties. These compounds are bonded to the surface of the textile and remain active long after free chlorine has evaporated or has been rinsed down the drain. When germs come into contact with this surface, the N-Halamine compounds penetrate and kill these microbes in the same way they would be killed by free chlorine.

The N-Halamine approach provides five distinct clinical benefits over surface-active antimicrobials and conventional biocides:

  1. Faster kill rate: Eliminates microbes in seconds or minutes, compared to hours or days for some other alternatives.
  2. Broader kill spectrum: Destroys a wide range of disease-causing microbes such as E. coli O157, Salmonella, MRSA staphylococci and foodborne and water-borne viruses, such as rotavirus, norovirus and polio.
  3. Longer functional life: Capable of being recharged with normal laundering with chlorine bleach, remaining effective for years.
  4. Superior safety: Limits exposure of workers and the environment to "free" chlorine.
  5. Mutation resistant: Avoids microbe resistance and mutation.

Chlorine's atomic structure in the form that is bound in N-Halamine makes it highly reactive with other atoms and molecules, because its outer shell is missing just one electron. Stabilizing chlorine in the N-Halamine makes it controllable, capable of remaining in place and active on materials including cotton, synthetics and vinyl. Applications include clothing, gloves, coverings and even floors. The stabilized chlorine retains its ability to interact with molecular targets on the surfaces of bacteria and other microbes, and kills them.

With an N-Halamine surface treatment, chlorine from chlorine bleach sanitizers remains highly effective at the surface or point of contact, making it much more efficient than conventional biocidal sprays, solutions or treatments like Triclosan or silver. These products typically are much slower in action and therefore less potent and useful in a food hygiene setting.

Speed and Spectrum of Biocidal Properties

When charged by exposure to sources of free chlorine, treated surfaces exhibit highly biocidal properties on contact with microbial organisms, rather than depending on the release of chlorine into the surrounding environment.

Lab testing was conducted by exposing N-Halamine treated fabrics to sodium hypochlorite bleach solutions, followed by extensive rinsing in de-ionized water, so that the control surfaces showed little to no residual antimicrobial activity due to the presence of free chlorine, and the fabrics were allowed to dry. Charged substrates were then stored in the dark at 20° C for periods ranging up to six months, and removed for visual and analytical or microbiological testing at intervals to determine the longevity of the chlorine charge.

Chlorine bleach-charged coatings on textiles showed potent activity against a wide spectrum of microbes, including yeasts, viruses and fungi, even when contact times were as short as a few minutes. This evidence of the persistence of chlorine suggests the strong likelihood that charged surfaces may be protected for at least weeks, and in some instances, months, depending on the susceptibility of the target microbes.

While observations indicate that bound chlorine may be gradually diminished over a period of months. Subsequent re-exposure to free chlorine resulted in the rapid recharge, demonstrating that the N-Halamine was not removed by laundering and remained bound firmly to the surface.

Surfaced treated N-Halamine products are already widely used in health care settings, where sanitary conditions are equally critical. Requiring just normal laundering practices, N-Halamine-treated antimicrobial uniforms and gloves may fill a critical gap in plant sanitation policies, particularly as the need for improved safeguards against contamination across the food processing industry becomes more critical.

Dr. Jeff Williams is chief technology officer for Vanson HaloSource, the bioscience company that develops antimicrobial technologies for applications in health care, industrial, water treatment and home markets. He can be reached at 425-881-6464 or jwilliams@vanson.com.

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