Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using direct contact with electrical or electromagnetic...
Reexamination Certificate
1998-10-30
2001-07-17
Till, Terrence R. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using direct contact with electrical or electromagnetic...
C422S023000, C422S028000, C422S292000, C422S906000, C422S907000, C250S455110
Reexamination Certificate
active
06261518
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a plasma sterilization process and apparatus comprising pulsed treatment with a gaseous or vaporized antimicrobial agent such as hydrogen peroxide or a peracid to kill microorganisms and spores on the article. In particular, this invention relates to exposing an article to be sterilized to a plurality of treatment cycles, each cycle including cyclic pulses of a gaseous or vaporized antimicrobial agent at one pressure, followed by pressure reduction to a lower pressure. The article is then exposed to a gas plasma. The article to be sterilized may include a container or enclosure whose interior is required to be sterilized.
BACKGROUND OF THE INVENTION
A variety of gas sterilization methods has been investigated in the past. Methods using ethylene oxide and other disinfecting gases are widely used for sterilizing a wide range of medical products from pharmaceutical preparations to surgical instruments. Irradiation alone or together with disinfecting gases has also been investigated, as summarized by Russell, A. THE DESTRUCTION OF BACTERIAL SPORES. New York: Academic Press (1982).
A sterilizing method must effectively kill all organisms, including spores, without damage to the article or goods being sterilized. However, many disinfecting gases which meet this criterion, such as ethylene oxide and irradiation methods have been recognized to expose workers and the environment to safety hazards. States and Federal legislation are severely restricting the amount of hazardous gases such as ethylene oxide (a carcinogen) in the working environment, or the use of any system or method which produces toxic residues or exhaust products. This is presenting a major crisis in hospitals and other areas of the health industry.
DESCRIPTION OF THE PRIOR ART
Sterilizing plasmas have been generated with a wide variety of gases: argon, helium or xenon (U.S. Pat. No. 3,851,436); argon, nitrogen, oxygen, helium or xenon (U.S. Pat. No. 3,948,601); glutaraldehyde (U.S. Pat. No. 4,207,286); oxygen (U.S. Pat. No. 4,321,232); oxygen, nitrogen, helium, argon or Freon with pulsed pressure (U.S. Pat. No. 4,348,357); hydrogen peroxide (U.S. Pat. Nos. 4,643,876 and 4,756,882); nitrous oxide, alone or mixed with oxygen, helium or argon (Japanese Application Disclosure No. 103460-1983); and nitrous oxide, alone or mixed with ozone (Japanese Application No. 162276-1983). Unfortunately, these plasmas have proven to be too corrosive to articles being sterilized and particular packaging materials; have left toxic residues on the sterilized articles; or have presented safety or environmental hazards.
Typical prior art plasma sterilizing systems such as U.S. Pat. No. 4,643,876 have a combined chamber where both plasma generation and sterilization take place. The plasma is generated from hydrogen peroxide vapor and residue, and the article being sterilized is directly exposed to the plasma inducing electromagnetic field. The in situ generation of the ions and free radicals in the vicinity of the article surface is considered to be a critical part of the static process. Antimicrobial hydrogen peroxide pretreatment has been combined with exposure of the article to the electromagnetic plasma generating environment to remove any remaining hydrogen peroxide residues. The process is static, that is, the plasma is generated in the volume of gas initially in the closed chamber, and the articles are not exposed to plasma generated from a mixture of hydrogen, oxygen and inert gases, as in the process of this invention. These systems tend to rapidly decompose plastic and cellulose containing packages because of the strong oxidizing properties of the ions and free radicals in the elevated temperatures of the process. Limiting the process time to prevent package destruction also produces an inadequate spore kill rate.
Plasma gas sterilizer systems described in U.S. Pat. Nos. 3,851,436 and 3,948,601 comprise separate plasma RF generation chamber and sterilizing chamber. A gas plasma produced in the plasma generating chamber with argon, helium, nitrogen, oxygen or xenon is passed into a separate sterilization vacuum chamber.
Non-plasma gas sterilization procedures have been described using ozone (U.S. Pat. No. 3,704,096) and hydrogen peroxide (U.S. Pat. Nos. 4,169,123, 4,169,124, 4,230,663, 4,366,125, 4,289,728, 4,437,567 and 4,643,876). These materials are toxic or corrosive and leave undesirable residues.
Peracid sterilization processes have been disclosed in East German Patent Application Serial No. 268,396, EPO Patent Application Publication No. 109,352 A1, and U.K. Patent 2,214,081, for example. The sporicidal activities of peracetic acid, alone and in combination with other compounds including ethanol and hydrogen peroxide are disclosed by Leaper, S., Food Microbiology. 1:199-203 (1984); Leaper, S. et al, J. Applied Biol. 64:183-186 (1988); Leaper, S., J. Food Technology. 19:355-360 (1984); and Leaper, S., J. Food Technology. 19:695-702 (1984). These methods are not effective to sterilize the contents of packages containing cellulose and other materials which are reactive with peracid species.
The use of plasma to sterilize containers was suggested in U.S. Pat. No. 3,383,163.
The above apparatus and methods do not achieve complete sterilization for many types of articles requiring sterilization, and most produce damage to articles and packaging in the course of producing high sterilization rates. As a result, they do not achieve the necessary goal of providing an all purpose, effective sterilizing system and process.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved plasma sterilizing process which carries out effective sterilization quickly, with no toxic residues and with emissions which present no environmental safety hazard and without damage to articles, including those that are packaged or in the form of a container.
It is another object of this invention to provide an economical sterilizing process which is safe and effective for use in a hospital environment.
It is another object of the present invention to provide an efficient process which achieves sterilization with all types of articles used in the health care environment, including metallic articles and articles contained in porous sterilization packaging including cellulosic materials.
It is also another object of the present invention to provide an efficient and cost-effective process for sterilization of vessels or chambers such as lyophilizers or sterile isolation enclosures.
These and additional objects are accomplished by the method of this invention for plasma sterilization which comprises exposing an article in a sterilizing chamber to at least one combination sterilizing cycle. In the case where the article to be sterilized is the interior of a container, the container itself may function as a sterilizing chamber connectable to a plasma source and an antimicrobial source. Each sterilizing cycle is comprised of a pulsed treatment with gaseous antimicrobial agent, removal of the gaseous antimicrobial agent, and a plasma treatment. The pulsed treatment comprises one or more pulse-vacuum cycles, each pulse-vacuum cycle comprising the steps of evacuating the sterilizing chamber and exposing the article to the gaseous antimicrobial agent for a predetermined duration. After the pulsed treatment, the antimicrobial agent is removed by evacuating the sterilizing chamber. The plasma treatment comprises exposing the article to a stream of plasma having essentially uncharged, highly reactive free radicals which are oxidizing or reducing agents. The plasma is generated in a separate plasma generating chamber and is supplied to effect sterilization in the sterilization chamber. The pulsed treatment and the plasma treatment follow a predetermined order in each combination sterilizing cycle.
According to one aspect of the invention, the antimicrobial agent is preferably selected from the group consisting of hydrogen peroxide, a peracid antimicrobial agent, or mixtures thereof, the pe
Amsler Thomas J.
Campbell Bryant A.
Campbell Louise A.
Caputo Ross A.
Du Kangyan
Barnes & Thornburg
Campbell Louise A.
DePuy Orthopaedics, Inc.
Snider Theresa T.
Till Terrence R.
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