[Triclosan is hidden in many household and personal care items under
different naes. ; The chemical name for Triclosan is
2,4,4'-Trichloro-2'-hydroxydiphenyl ether. CAS#
3380-34-5. Other names: Microban, Irgasan DP-300, Lexol 300,
Ster-Zac, Cloxifenolum, Biofresh (still more) -- Catherine]
Germ Warfare
Jennifer Medlin
A new breed of antimicrobial polymers is at work waylaying the growth
of potentially harmful bacteria, molds, and fungi in an array of
industrial, institutional, and consumer products. Developed by a trio
of North Carolina biomedical engineers at Microban Products Company,
the antimicrobial additives go into the products and materials they
protect during the manufacturing process, yielding an inherently
effective defense against the growth of microbes--and a protection
that won't wash off or wear away. Independent laboratory tests have
consistently shown dramatic reductions in microbial populations
present on materials manufactured with Microban.
A large number and variety of products now incorporate Microban
including kitchen cutting boards, dental instrument trays, surgical
incise drapes, socks, bedding, food-service wipes, and even concrete
and industrial drains. The list is growing, thanks to the demand by
companies seeking to infuse antimicrobial properties into their
products and the public's blossoming awareness of the ravages these
omnipresent microbes can inflict on the human body.
The Quest for Cleanliness The quest for cleanliness is hardly new.
During World War I, the Germans discovered that antimicrobial
treatments for uniforms worn by soldiers engaged in trench warfare
lowered the incidence of secondary wound infections. However, until
now, virtually all antimicrobial treatments were applied topically.
Topically applied finishes (for example quaternary ammonium compounds
in silicone carriers) eventually wear off. Ironically, the same kind
of "wear and tear" that erodes these coatings and renders them
ultimately ineffective actually triggers the release of more Microban
molecules at the surface of the material. The activation of these
molecules from abrasion yields permanent effectiveness over the
product's lifetime.
The development of Microban's antimicrobial polymers evolved over a
period of several years. Since their days at Bristol-Myers' medical
products division, Microban President Glenn Cueman and his cofounders
Henry Richbourg and Barnwell Ramsey had product development in their
blood. They also understood the critical need for clean medical
environments. In 1987, they left Bristol-Myers--each of them with a
15-year tenure behind them--to form Clinitex Corporation, the
forerunner of Microban. Clinitex produced orthopedic and specialty
medical devices and related products for hospitals and long-term care
facilities, as well as for in-home medical care.
"Back in the '70s and '80s, we were constantly looking for a way to
improve medical devices," Cueman recalls. "Control of microorganisms
was tops on that list."; For years, the medical community relied on
steam, gas, or radiation to kill harmful microorganisms. And even with
procedures like iodine scrubs and alcohol preps, there was always the
fear that a patient might leave the hospital with an illness worse
than the one he or she had coming in, Cueman says. The whole
environment poses a threat to surgery patients, from surgical drapes
that harbor germs to the heating and air-conditioning ducts that spew
air contaminated by colonies of molds and mildew.
"That was where we began our quest," says Cueman. He and his
colleagues wanted to make a material that would be inherently
resistant to microbial contamination. They knew that heavy metals such
as arsenic, copper, zinc, and silver were microbe-resistant and could
be extruded during the polymer manufacturing process, but that such
materials were often unsuitable or unsafe for human contact. Instead,
they sought to find a compound that "was well-documented for contact
with human skin,"; Cueman says, then to encapsulate it and introduce it
into a product during the manufacturing process.
Antimicrobial Protection Power pellets. In laboratory tests,
bacteria-free zones surround antimicrobial pellets (red and yellow).
Credit: Microban Products Company
Just how these molecules defeat pathogenic microorganisms including
Escherichia coli and Salmonella enteritidis is a small miracle. Using
the Microban process, synthetic fibers or plastics incorporate pellets
encapsulating high concentrations of antimicrobial additives. These
additives differ according to the chemical makeup of the product for
which the pellets are eventually destined. According to Cueman, the
pellets look identical to the polymers Microban customers use to make
their products, and are handled the same way during the manufacturing
process.
";There's a different [additive development] process for each type of
material being made,"; Cueman says. For example, when the eventual
product is socks, "The manufacturer will solubilize our product, then
repolymerize it during the fiber extrusion process," Cueman explains.
"Basically, we're a custom formulator. We have a database that shows
how much [of the additive] to use for each application," he says.
For example, a cutting board with the Microban additive is formed from
polyethylene pellets one-tenth of an inch square. Except for
containing the antimicrobial ingredient, Microban pellets are the same
color and composition as the basic material, Cueman explains, and
";become intimately blended, part of the product's molecular
structure." The synthetic additive retains its antimicrobial
properties for the life of the fabric or plastic into which it is
formulated, and it is not water-soluble. According to independent
tests by several laboratories, the additives are noncarcinogenic and
nonallergenic to the skin. Depending on the application, the additives
also bear the stamp of FDA approval or EPA registration.
The trick to the Microban ingredient's function is introducing it into
the polymer's amorphous phase. "We don't want it to chemically react
or cross-link," says Cueman. Because these molecules exist in the
amorphous phase, they are free to migrate within the polymer, and do
so when the product's surface is abraded--when, for example, a cutting
board, sock, or mattress pad is used or washed.
The additive remains within the interstitial spaces of the fiber or
plastic's polymeric backbone. Suspended there, the additive is free to
migrate to the surface, reactivating the product's antimicrobial
properties. Microban's effectiveness is due in part to the low
concentration of Microban additive dispersed throughout the material,
with surface concentrations measured in micrograms per gram. Even
though the Microban additives are dispersed into lower concentrations
in the finished products, thousands of tests have shown them to be
effective on a number of microorganisms, including gram-positive and
gram-negative bacteria, ammonia-producing bacteria, fungi,
dermatophytes, resident skin bacteria, molds, and yeasts. And, says
Cueman, the product is both safe and permanent.
The front lines. New products containing antimicrobial polymers
include children's chairs, mattress pads, and countertops. Credit:
Microban products Company
The Microban additives lie in ambush, waiting for unsuspecting
microorganisms, then rupture their cytoplasmic membrane. This in turn
releases a leakage of low-molecular-weight cellular material, which
prevents the uptake of amino acids essential to further cellular
growth. Like pins patiently poised to pierce a falling balloon,
Microban pellets penetrate the thin cellular walls of the tiniest
microorganisms. Thicker cell walls--such as those of human cells and
insect cells, for example--remain impervious to this cellular
invasion. So, while the antimicrobial additive is effective on
bacteria and fungi, it is harmless to higher life forms. And, once |