cone oil—on the insides of syringes for nearly half a century to
ensure the smooth movement of the plunger during injection.
The oil, however, can clump certain bioengineered proteins, it
can turn certain drugs cloudy and it also can alter the shelf life
of some pharmaceuticals.
Yet companies continue to use the oil.
“About two years ago, I chaired a discussion group
where people talked about all the problems with a certain
technology,”recalled David Opie, Ph.D. “The morning of that
conference, we heard people talk about alternatives to that tech-
nology, but no one was using those alternatives. I asked the pan-
el why they were still discussing the problems with the original
technology when we heard about alternatives that don‘t have the
same issues. One guy said, ‘No one’s ever been fired for choosing
the status quo.’ That’s it in a nutshell. No one is willing to put
their career on the line to risk a product line in which millions
of dollars are invested for the hope of something better because
they have the devil they know. They have problems with the cur-
rent technology and they don’t know what problems might arise
when they try to implement the new technology. People see that
unknown as a risk to their career and a risk to the product line.
It’s that risk that really steers the decision-making and adoption
of new technologies across the board. Change is hard ... no one
wants to be first.”
Certainly not. But medtech companies may have no other
choice—cost pressures, federal/international regulations, envi-
ronmental concerns and device complexity are nudging them
toward previously uncharted territory in sterilization techniques.
Blazing new trails are technologies such as nitrogen dioxide
(NO2), X-ray and supercritical carbon dioxide (SCCO2), the latter of which is used mostly in the orthopedic industry to sterilize bone, tendon, skin and other allograft tissue. Developed by
Lansing, N.Y.-based NovaSterilis Inc., SCCO2 is neither a gas
nor liquid, but rather carbon dioxide in a“fluid state,”the point at
which its temperature and pressure are equal to or greater than
the critical point ( 31.1 degrees Celsius, 74 atm).
By falling within the gas-liquid spectrum mid-point, supercritical fluids inherit the talents of both forms of matter—they can
diffuse through solids like a gas, and dissolve materials like a liquid. Such non-committal, along with its density, solvency, gas-like
viscosity, compressibility and low surface tension, enables SCCO2
to better penetrate bone and allograft tissue without damaging
their structural or chemical integrity, the company claims. As a result, the process completely kills infectious organisms that might
be missed by traditional bone sterilization methods like gamma
radiation and cold washings with disinfecting solutions.
Since it converts to its supercritical (fluid) stage at a relatively low pressure and temperature, SCCO2 is ideal for materials that are heat-sensitive or reactive with other sterilization methods. It is non-toxic, non-flammable, chemically inert,
comparably inexpensive, and can easily be removed from a
system by simple depressurization.
NovaSterilis’s Nova 2200 features a 20-liter sterilization cham-
ber in which up to 60 individual allografts (transplant tissues)
can be purified. To deactivate spores as well as live bacteria, the
company provides sheets of paper treated with a mix of chemical
additives including an acid that can be dissolved into the super-
critical SCCO2 sterilizing fluid, much like detergent in a washing
machine. The fluid penetrates bacterial cells and kills them.
SCCO2 sterilization slowly is gaining popularity and accep-
tance in the medtech industry, having been used to sanitize re-
generative materials, biologic scaffolds and resorbable polymers
ranging from poly-L-lactide and poly-D-lactide to L-lactide, DL-
lactide and L-lactide/glycolide. Sutures could soon be added to
the mix—last spring, NovaSterilis received a patent to remove
toxic ethylene oxide (EO) residuals from absorbable sutures fol-
lowing sterilization. In working to obtain the patent, the compa-
ny eliminated the need for EO sterilization altogether, achieving
a Sterility Assurance Level of 10-6, with SCCO2 maintaining the
“This new application can be applied across many classes of
products that are sterilized with EO, potentially improving the
performance of the product and outcomes of procedures uti-
lizing these devices,” NovaSterilis President David Burns said
upon the issuance of U.S. Patent No. 8658091.“We are confident
this process can be expanded to a broad range of products and
chemicals including, for example, the removal of residual sol-
vents from pharmaceuticals.”
A legion of possibilities truly exists as the company attempts
to branch into other sectors: Its SCCO2 technology already has
infiltrated supranamics manufacturing, industrial degreasing,
silicon wafer cleaning and textile dyeing. Vaccine/pharmaceutical
purification and materials coatings are on the horizon as well.
The technology also is becoming more widespread within
healthcare. More than a half-dozen U.S. tissue banks use SCCO2
to clean bone, tendon and other products; Australian Biotech-
nologies Pty. Ltd. received government approval in 2012 to mar-
ket SCCO2-sterilized cortical and cancellous bone products; and
a Dutch tissue processor/contract manufacturer is distributing
SCCO2-treated allografts in Europe, India, China and Malaysia.
Indeed, the supercritical sterilization approach is gaining
quite a toehold in the medtech arena. Yet many tissue banks are
hesitant to invest in the new technology even though it can help
suppliers significantly reduce costs by bringing the sterilization
process in-house. In addition, the SCCO2 process—like gamma
irradiation—can be performed while samples are sealed within
their final packaging, reducing the opportunity for the reintro-
duction of contaminants.
Nevertheless, surgeons are optimistic about the future of su-
percritical sterilization.“I see the process becoming a standard in
the industry,” one medtech executive speculated.
X-rays carry the same potential.
X-radiation is a viable alternative to hydrogen peroxide, steam
and other traditional cleaning methods due to advancements in
high-energy, high-power electron accelerators. Belgian firm Ion
Beam Applications S.A. (IBA) is a pioneer in the field, having developed a particle accelerator in 1992 from a patented concept
of the French Atomic Energy Commission. The company offers