Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
  • A61L2/02—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor using physical phenomena
  • A61L2/14—Plasma, i.e. ionised gases
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/2406—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/2406—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes
  • H05H1/2443—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes the plasma fluid flowing through a dielectric tube
  • H05H1/245—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes the plasma fluid flowing through a dielectric tube the plasma being activated using internal electrodes
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H2245/00—Applications of plasma devices
  • H05H2245/30—Medical applications
  • H05H2245/36—Sterilisation of objects, liquids, volumes or surfaces

Definitions

• the present disclosure relates generally to the sterilization or disinfection of medical apparatus and articles, and more particularly to the application of a gas plasma with reactive species to effect sterilization or disinfection of medical articles such as medical instruments or medical endoscope lumens.
• ethylene oxide is an excellent sterilizant and penetrates well into the lumens of, e.g., endoscopes, ethylene oxide also exhibits undesirable toxicity and flammability, and for at least these reasons, the art has sought alternatives.
• the present disclosure provides a sterilization or disinfection system employing an oxygen/nitrogen plasma as the sterilizing gas.
• the disclosed embodiments permit a high electrode energy density while minimizing unwanted heat production.
• the present disclosure relates to a system including a plasma generator.
• the plasma generator includes an electrode, a shield, and a dielectric gap between the electrode and the shield.
• a source of electrical power is connected to the plasma generator for applying an electrode energy density between the electrode and the shield.
• a source of gas provides a gas flow through the plasma generator to form from the gas a plasma containing acidic and/or oxidizing species.
• the system may also include a device for conveying an article undergoing sterilization through a chamber fluently connected to the source of the gas.
• the gas includes one or more species selected from the group consisting of molecular oxygen, molecular nitrogen, nitric oxide, nitric acid, and nitrous oxide.
• the gas includes water vapor, molecular oxygen, and molecular nitrogen.
• the gas comprises air.
• the relative humidity of the gas entering the plasma generator is at least 21%.
• the temperature at the surface of the shield is preferably maintained at less than 150 °C when the electrode energy density is greater than 0.05 eV/molecule of the gas passing between the electrode and the shield.
• the source of electrical power is a pulsed DC source having a high dV/dT.
• the system further includes a cooling apparatus.
• the system includes a filter for removing the acidic and/or oxidizing species from the gas.
• the present disclosure describes a method for sterilizing a contaminated article using a sterilizer including a plasma generator having an electrode, a shield, and a dielectric gap between the electrode and the shield, a source of electrical power connected to the plasma generator for applying an electrode energy density between the electrode and the shield, and a source of gas providing a flow through the plasma generator to form a plasma containing acidic and/or oxidizing species from the gas.
• the gas containing the acidic and/or oxidizing species is directed from the plasma generator into an enclosed area including the portions of the article undergoing sterilization.
• the gas includes water vapor, oxygen, and nitrogen, and the temperature at the surface of the shield is maintained at less than 150 °C when the electrode energy density is greater than 0.05 eV/molecule of the gas passing between the electrode and the shield.
• the contaminated article is exposed to the gas containing the acidic and/or oxidizing species for an exposure time sufficient to sterilize the contaminated article, which is preferably no more than one hour.
• the present disclosure describes a method of disinfecting a
• a disinfecting system having a plasma generator having an electrode, a shield, and a dielectric gap between the electrode and the shield, a source of electrical power connected to the plasma generator for applying an electrode energy density between the electrode and the shield, and a source of a gas comprising water vapor, oxygen, and nitrogen, configured to provide a flow of the gas through the plasma generator between the electrode and the shield to form a plasma containing acidic and/or oxidizing species from the gas.
• the gas containing the acidic and/or oxidizing species is directed from the plasma generator into an enclosed area including the portions of the article undergoing disinfection.
• the contaminated article is contaminated with at least one of a bio-film comprising a plurality of microorganisms, or a plurality of microbial or fungal spores.
• the contaminated article is exposed to the gas containing the acidic and/or oxidizing species for an exposure time sufficient to disinfect the contaminated article by achieving at least a 2-logio and optionally up to an 11-logio reduction in colony forming units of the disinfected contaminated article relative to the contaminated article.
• a system comprising:
• a plasma generator including:
• a source of electrical power connected to the plasma generator, for applying an electrode energy density between the electrode and the shield;
• a source of a gas comprising water vapor, oxygen, and nitrogen, configured to provide a flow of the gas through the plasma generator between the electrode and the shield to form a plasma containing acidic and/or oxidizing species from the gas;
• a temperature at the surface of the shield is maintained at less than 150 °C when the electrode energy density is greater than 0.05 eV/molecule of the gas passing between the electrode and the shield, optionally wherein the system further comprises a device for conveying an article undergoing sterilization through a chamber fluently connected to the flow of the gas through the plasma generator containing the acidic and/or oxidizing species.
• Embodiment B The system of Embodiment A, wherein the gas includes one or more species selected from the group consisting of molecular oxygen, molecular nitrogen, nitric oxide, nitric acid, and nitrous oxide.
• Embodiments A to D The system of any one of Embodiments A to D, further comprising a cooling apparatus.
• a method of sterilizing a contaminated article comprising:
• a sterilizer including:
• a plasma generator having:
• a source of electrical power connected to the plasma generator for applying an electrode energy density between the electrode and the shield;
• a source of a gas comprising water vapor, oxygen, and nitrogen, configured to provide a flow of the gas through the plasma generator between the electrode and the shield to form a plasma containing acidic and/or oxidizing species from the gas;
• Embodiment H further comprising removing at least a portion of the acidic and/or oxidizing species from the gas upon achieving the desired degree of sterilization of the article.
• Embodiment I wherein the removing at least a portion of the acidic and/or oxidizing species from the gas is performed with an apparatus comprising one or more materials selected from the group consisting of activated carbon, a species with a basic functionality, a species providing a basic adsorbent, a reducing species, and a molecular sieve.
• a method of disinfecting a contaminated article comprising:
• a disinfecting system including:
• a plasma generator having:
• a source of electrical power connected to the plasma generator for applying an electrode energy density between the electrode and the shield, and a source of a gas comprising water vapor, oxygen, and nitrogen, configured to provide a flow of the gas through the plasma generator between the electrode and the shield to form a plasma containing acidic and/or oxidizing species from the gas;
• the gas containing the acidic and/or oxidizing species from the plasma generator into an enclosed area enclosing at least a portion of the contaminated article, wherein the contaminated article is contaminated with at least one of a bio-film comprising a plurality of microorganisms, or a plurality of microbial or fungal spores;
• Embodiment V The method of Embodiment U, wherein the contaminated article is a medical device and the enclosed area is a hollow area of the medical device.
• Embodiment V wherein the medical device is an endoscope and the hollow area is a lumen of the endoscope, further wherein the gas containing the acidic and/or oxidizing species from the plasma generator is passed through the lumen of the endoscope.
• the bio-film comprises a plurality of microorganisms selected from the group consisting of Geobacillus stearothermophilus, Bacillus subtilis, Bacillus atrophaeus, Bacillus megaterium, Bacillus coagulans, Clostridium sporogenes, Bacillus pumilus, Aspergillus brasiliensis, Aspergillus oryzae, Aspergillus niger, Aspergillus nidulans, Aspergillus flavus, Clostridium difficile, Mycobacterium terrae, Mycobacterium tuberculosis, Mycobacterium bovis, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus epidermidis, Staphyolococcus lugdunensis, Staphylococcus saprophytics, Entero
• AA The method of any one of Embodiments U to Z, wherein the gas includes at least one species selected from the group consisting of molecular oxygen, molecular nitrogen, nitric oxide, nitric acid, and nitrous oxide.
• Embodiment AA wherein the gas comprises air.
• FIG. 1 is a schematic view of an exemplary sterilization system of the present disclosure.
• FIG. 2A is a cross-section view of one variant of a plasma generator taken along section lines 2-2 in FIG. 1.
• FIG. 2B is a cross-section view of another variant of a plasma generator taken along section lines 2-2 in FIG 1.
• FIG. 2C is a cross-section view of another variant of a plasma generator taken along section lines 2-2 in FIG 1.
• the present disclosure describes an apparatus and methods for sterilizing or disinfecting articles using a gas plasma including oxygen, nitrogen, and reactive species produced from these gases.
• the plasma is directed to a chamber in which the goods to be sterilized or disinfected are placed.
• the plasma is directed into the lumen of an apparatus or article requiring sterilization or disinfection.
• a viscosity of "about” 1 Pa-sec refers to a viscosity from 0.95 to 1.05 Pa-sec, but also expressly includes a viscosity of exactly 1 Pa-sec.
• a substrate that is “substantially” transparent refers to a substrate that transmits more radiation (e.g. visible light) than it fails to transmit (e.g. absorbs and reflects).
• a substrate that transmits more than 50% of the visible light incident upon its surface is substantially transparent, but a substrate that transmits 50% or less of the visible light incident upon its surface is not substantially transparent.
• the present disclosure describes a sterilization or disinfection system including a plasma generator.
• the plasma generator includes an electrode, a shield, and a dielectric gap between the electrode and the shield.
• a source of electrical power is connected to the plasma generator for applying an electrode energy density between the electrode and the shield.
• a source of gas provides a gas flow through the plasma generator to form from the gas a plasma containing acidic and/or oxidizing species.
• the system may also include a device for conveying an article undergoing sterilization through a chamber fluently connected to the source of the gas.
• the gas includes one or more species selected from the group consisting of molecular oxygen, molecular nitrogen, nitric oxide, nitric acid, and nitrous oxide.
• the gas includes water vapor, molecular oxygen, and molecular nitrogen.
• the gas comprises air.
• the relative humidity of the gas entering the plasma generator is at least 21%.
• the temperature at the surface of the shield is preferably maintained at less than 150 °C when the electrode energy density is greater than 0.05 eV/molecule of the gas passing between the electrode and the shield.
• the source of electrical power is a pulsed DC source having a high dV/dT.
• the system further includes a cooling apparatus.
• the system includes a filter for removing the acidic and/or oxidizing species from the gas.
• Sterilization/disinfection system 20 includes a source of gas 22, which comprises molecular oxygen and nitrogen.
• the gas from source 22 may be air or a specific blend including molecular oxygen and nitrogen at a specified ratio, and may be pressurized or unpressurized as provided. If from an unpressurized source 22, a compressor 24 may be used to pressurize the gas to a convenient pressure.
• the gas is then transported via line 26 to a flow controller 28 to meter the mass flow of gas to the rest of the sterilization system 20.
• Flow controller 26 may take the form of a pressure regulator, a ball-in-tube flowmeter, an electronic mass flow controller, or other similar device.
• the gas is then transported via line 30 to a humidification device 32 to bring the humidity of the gas to between about 1 and 50 g/m 3 , between 2 and 40 g/m 3 , between 3 and 30 g/m 3 , between 4 and 20 g/m 3 , or even between 5 and 15 g/m 3 .
• a humidification device 32 to bring the humidity of the gas to between about 1 and 50 g/m 3 , between 2 and 40 g/m 3 , between 3 and 30 g/m 3 , between 4 and 20 g/m 3 , or even between 5 and 15 g/m 3 .
• the humidified gas is conveyed via line 34 to an optional humidity detector 36 to verify that the humidity level is within the desired range.
• feedback control via control line 38 is provided to manipulate humidification device 30 appropriately.
• the humidified gas is transported via line 40 to a plasma generator 50, which will be discussed with more particularity below.
• Plasma generator 50 induces the production of diverse chemical species in the humidified gas, including one or more of nitrous acid, nitric acid, ozone, and nitrous oxide.
• This gas is conveyed to a remote location by line 52.
• line 52 may be quite long without losing sterilizing efficacy: distances between about 0.5 to 90 meters have been found to be suitable.
• Line 52 may, for example deliver sterilizing/disinfecting gas directly to an endoscope
• Gas leaves the endoscope 60 via line 62 and is conveyed to a filter 64 to render the gas harmless.
• the filter 64 will include an alkaline element such as sodium bicarbonate to neutralize any remaining acidic species.
• An element such as activated carbon to remove oxidizing species such as ozone is also conveniently present. After filtration, the gas can be released to ambient via outlet 66.
• FIG. 2A a cross-section view of one variant 50a of plasma generator 50 taken along section lines 2-2 in FIG. 1 is illustrated.
• the gas is conveyed through lumen 70 in outer tube 72.
• Tube 72 is a dielectric, conveniently glass.
• inner tube 74 having a lumen 76.
• Tube 74 is also a dielectric, conveniently glass.
• first electrode 80 Within lumen 76 is first electrode 80.
• a second electrode 82 surrounds the outer tube 72, and in some convenient embodiments has heat radiating fins 84 so that it serves additional duty as a heat sink.
• Other expedients may be used to provide cooling, such as a fan, fins, heat exchanger, piezoelectric cooling, and combinations thereof.
• first electrode 80 is the high voltage electrode and second electrode 82 is the ground electrode.
• An AC voltage of between about 4 to 12 kV is conveniently applied to first electrode 80, having a frequency of between about 4 to 30 kHz.
• the exact conditions depend on the gas flow needed to efficaciously treat the apparatus needing sterilization, the available cooling capacity for plasma generator 50, and the dimension of the outer and inner tubes 72 and 74 respectively. In any case, the electrical parameters must cause the conditions to exceed the breakdown voltage of the gas between the tubes.
• FIG. 2B a cross-section view of another variant 50b of plasma generator 50 taken along section lines 2-2 in FIG. 1 is illustrated.
• the gas is conveyed through lumen 90 in tube 92.
• Tube 92 is conveniently polymeric tubing such a polytetrafluoroethylene (PTFE).
• PTFE polytetrafluoroethylene
• ribbon cable 94 including a first conductor 96, a second conductor 98, conveniently both within a dielectric insulation 100.
• FIG. 2C a cross-section view of one variant 50c of plasma generator 50 taken along section lines 2-2 in FIG. 1 is illustrated.
• the gas is conveyed through lumen 110 in tube 112.
• Tube 112 is conveniently polymeric tubing such a polytetrafluoroethylene (PTFE).
• electrode subassembly 114 comprising electrode 116, conveniently the high voltage electrode, surrounded by a dielectric layer 118.
• dielectric layer 118 is another electrode 120, conveniently the ground electrode. Fins 122 be conveniently be present to improve the electric field being generated.
• first conductor 96 is the high voltage electrode and second conductor 98 is the ground electrode.
• the rise of the pulse the highest instantaneous rate of change of the voltage should reach a rate of at least 10 kV/nano-sec, at least 20kV/nano-sec, at least 30 kV/nano-sec, at least 40 kV/nano-sec, or even at least 50 kV/nano-sec.
• This type of charging allows plasma to be generated within the gas with relatively little heating.
• the sterilization system includes a plasma generator having an electrode, a shield, and a dielectric gap between the electrode and the shield, a source of electrical power connected to the plasma generator for applying an electrode energy density between the electrode and the shield, and a source of gas providing a flow through the plasma generator to form a plasma containing acidic and/or oxidizing species from the gas.
• the gas containing the acidic and/or oxidizing species is directed from the plasma generator into an enclosed area including the portions of the article undergoing
• the gas includes water vapor, oxygen, and nitrogen, and the temperature at the surface of the shield is maintained at less than 150 °C when the electrode energy density is greater than 0.05 eV/molecule of the gas passing between the electrode and the shield.
• the contaminated article is exposed to the gas containing the acidic and/or oxidizing species for an exposure time sufficient to sterilize the contaminated article, which is preferably no more than one hour.
• the method further includes removing at least a portion of the acidic and/or oxidizing species from the gas upon achieving the desired degree of sterilization of the article.
• Removing the acidic and/or oxidizing species from the gas may be performed with an apparatus including one or more adsorbent or absorbent materials selected from activated carbon, a chemical species with a basic functionality (e.g. , an organic amine, sodium hydroxide, potassium hydroxide, lithium hydroxide, and the like), a species providing a basic adsorbent (e.g. a basic ion exchange resin), a reducing species (e.g., one or more active metals such as platinum, palladium, and the like), and a molecular sieve.
• adsorbent or absorbent materials selected from activated carbon
• a chemical species with a basic functionality e.g. , an organic amine, sodium hydroxide, potassium hydroxide, lithium hydroxide, and the like
• removing the acidic and/or oxidizing species from the gas may be performed by directing the gas through a catalytic reducer.
• the enclosed area is a sterilization chamber.
• the article undergoing sterilization is a medical device and the enclosed area is a hollow area of the medical device.
• the medical device is an endoscope and the hollow area is the lumen of the endoscope, and the gas containing the acidic and/or oxidizing species from the plasma generator is passed through the lumen of the endoscope.
• the medical device is a medical instrument and the hollow area is at least one internal cavity of the medical instrument.
• Certain embodiments of the present disclosure also describes a method of disinfecting a contaminated article, including providing a disinfecting system having a plasma generator having an electrode, a shield, and a dielectric gap between the electrode and the shield, a source of electrical power connected to the plasma generator for applying an electrode energy density between the electrode and the shield, and a source of a gas comprising water vapor, oxygen, and nitrogen, configured to provide a flow of the gas through the plasma generator between the electrode and the shield to form a plasma containing acidic and/or oxidizing species from the gas.
• the gas containing the acidic and/or oxidizing species is directed from the plasma generator into an enclosed area including the portions of the article undergoing disinfection.
• the contaminated article is contaminated with at least one of a bio-film comprising a plurality of microorganisms, or a plurality of microbial or fungal spores.
• the contaminated article is exposed to the gas containing the acidic and/or oxidizing species for an exposure time sufficient to disinfect the contaminated article by achieving at least a 2-logio and optionally up to an 11-logio reduction in colony forming units of the disinfected contaminated article relative to the contaminated article.
• the article undergoing sterilization is a medical device and the enclosed area is a hollow area of the medical device.
• the medical device is an endoscope and the hollow area is the lumen of the endoscope, and the gas containing the acidic and/or oxidizing species from the plasma generator is passed through the lumen of the endoscope.
• the bio-film comprises a plurality of microorganisms selected from spores such as, for example, Geobacillus stearothermophilus, Bacillus subtilis, Bacillus atrophaeus, Bacillus megaterium, Bacillus coagulans, Clostridium sporogenes, Bacillus pumilus, Aspergillus brasiliensis, Aspergillus oryzae, Aspergillus niger, Aspergillus nidulans, Aspergillus flavus, Clostridium difficile; bacterial cells such as, for example, Mycobacterium terrae, Mycobacterium tuberculosis, and Mycobacterium bovis; and biofilm-forming bacteria such as, for example Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus epidermidis, Staphyolcoccus lug
• the contaminated article is contaminated with a bio- film including a plurality of microorganisms
• the exposure time is at least 5 minutes
• the reduction in colony forming units of the disinfected article relative to the contaminated article is from 4-logio to 9-logio. More preferably, the reduction in colony forming units of the disinfected article relative to the contaminated article is from 5-logio to 9-logio; from 6-logio to 9-logio; or even from 6-logio to 9-logio.
• the exposure time to achieve the desired level of disinfection of the contaminated article contaminated with a bio-film including a plurality of microorganisms is selected to be at most one hour. More preferably, the exposure time to achieve the desired level of disinfection is no greater than 50 minutes, 40 minutes, 30 minutes, 20 minutes, or even 10 minutes. Most preferably, the exposure time to achieve the desired level of disinfection is selected to be at most 9 minutes, 8 minutes, 7 minutes, 6 minutes, 5 minutes, or as low as 4 minutes, 3 minutes, two minutes, or even 1 minute
• the contaminated article is contaminated with a bio- film including a plurality of microbial or fungal spores
• the exposure time is at least 2 minutes
• the reduction in colony forming units of the disinfected article relative to the contaminated article is from 6-logio to 10-logio. More preferably, the reduction in colony forming units of the disinfected article relative to the contaminated article is from 7-logio to 10-logio; from 8-logio to 10-logio; or even from 9-logio tolO-logio.
• the exposure time to achieve the desired level of disinfection of the contaminated article contaminated with a bio-film including a plurality of microbial or fungal spores is selected to be at most one hour. More preferably, the exposure time to achieve the desired level of disinfection is no greater than 50 minutes, 40 minutes, 30 minutes, 20 minutes, or even 10 minutes. Most preferably, the exposure time to achieve the desired level of disinfection is selected to be at most 9 minutes, 8 minutes, 7 minutes, 6 minutes, 5 minutes, or as low as 4 minutes, 3 minutes, two minutes, or even 1 minute
• Clostridium sporogenes ATCC® 3584TM (ATCC), Manassas, VA
• Mycobacterium smegmatis (ATCC® 14468TM) (ATCC), Manassas, VA
• Geobacillus stearothermophilus spore solution ( ⁇ lxl0 8 Colony Forming Units per mL (CFU/mL), vortexed for 1 minute) were drop-cast onto the films. All spores were kept in a refrigerator at 4°C between uses. The films containing -lxlO 6 spores/film were left to sit with the petri the dish lid open for > 1 h to ensure that the spore films were fully dry. Next, the films were inserted into 3- inch (7.62 cm) long PTFE sample tubes simulating an endoscope using clean tweezers with 3 films per sample tube. The films were inspected to make sure there was no significant overlap in the spore spot and that the films were in the PTFE tube with the spores face up.
• the films were immediately transferred to 50 milliliter (mL) tubes containing 25 mL of IX phosphate buffered saline (PBST) to neutralize the pH and all charged plasma species.
• PBST IX phosphate buffered saline
• the IX PBST was prepared from 100 mL of 10X PBS, 900 mL of deionized water and 1 g of polyethylene glycol sorbitan monooleate surfactant commercially available as TWEEN 80 from Sigma-Aldrich of St. Louis, MO.
• the IX PBST solutions were mixed for 5 minutes on a stir plate and were then vacuum filtered with 0.2 micrometer ( ⁇ ) pore size vacuum filter to ensure sterility and stored at 4°C.
• the spore films in IX PBST were vortexed, then sonicated for 20 min and vortexed an additional time to ensure all of the spores were removed from the surface.
• the colony forming units were counted using the PETRIFILM PLATE READER, commercially available from 3M Company. In each case the control samples of untreated spore films were used as the standard. For ideal quantification of kill, the number of CFU per plate was quantified in the range of 20-200. Based on the number of CFU and the known dilution concentration, it was possible to calculate the number of original CFU from the controls or treated spore films and quantify spore kill.
• a sterilization system generally as described in FIG. 1, and having a plasma generator generally as described in FIG. 2B was provided. More specifically, the plasma generator was constructed by feeding parallel electrodes composed of two strands of 3M Color Coded Flat Cable 3302, commercially available from 3M Company of St. Paul, MN into PTFE tubing having an lumen 3/16 inch (4.76 mm) in inside diameter. The anode and cathode were separated on a PVC backing at 0.05 inch (1.27) center-to-center spacing.
• DC pulsed power was supplied by a power supply commercially available as FPG 50-1NM from FID GmbH of Burbach, DE. The power was set to provide a square pulse with a pulse width of 10 ns and a variable pulse repetition rate and a variable voltage. Power measurements were taken with a homemade E-dot and B-Dot probe.
• Flow rates of oxygen and nitrogen gas from tanked sources were controlled using MKS mass flow controllers commercially available from MKS Instruments of Andover, MD.
• the gasses were mixed and subsequently humidified before being transported to the plasma generator.
• the plasma byproducts were further transported through connected tubing in order to measure the downstream response.
• PET film samples which had been inoculated with spores were inserted at recorded lengths within the tubing. In all cases, the spores are downstream from the plasma, outside of the afterglow region. In some cases, the plasma composition was monitored downstream past the spore films using Fourier-Transform Infrared (FTIR) Spectroscopy.
• FTIR Fourier-Transform Infrared
• processing parameters including voltage, repetition rate (pulse repetition frequency, PRF), and gas flow rate were changed independently and the mean logio of G. stearothermophilus was observed and recorded.
• the parameters were altered independently (all others held constant) of values in Table 1. The process values were then normalized according the equation:
• V 2 /R The energy term (V 2 /R ) was taken from I-V measurements on the device. The process values and results are recorded in Table 3.
• a sterilization system generally as described in FIG. 1, and having a plasma generator generally as described in FIG. 2A was provided. More specifically, the ozone generator tube available from Ozonefac Co. (Guangzhou, Guangdong, China) as part of the CT-AQ8G ozone machine was utilized as the plasma electrode. Power was coupled to the plasma electrode from 12 kHz ac power supply with a voltage of 3.6 kV and a total power of 85 W. Oxygen and nitrogen gasses were introduced in the plasma electrode at rates of 0.5 and 2.5 standard liter per minute (SLM), respectively. The gas precursor was humidified with 8.3 g/m 3 of vaporized water.
• SLM standard liter per minute
• the following Examples describe a plasma disinfection method useful to achieve microbial kill of mature biofilm found in lumened medical devices such as endoscopes.
• the plasma disinfection method provides a 6-log reduction in bacteria after 5 minutes of treatment.
• the disinfection method works on flexible lumened surfaces such as the interior channels of an endoscope.
• the disinfection method is effective in the presence of moisture and therefore integrates well in the current reprocessing procedures used to decontaminate endoscopes.
• reprocessed endoscopes that have been manually cleaned can be treated with the plasma disinfection method before they are exposed to a high level of disinfection or even sterilization.
• high level disinfected scopes can be treated with plasma immediately after the automated endoscope reprocessing (AER) cycle and before storage in a drying cabinet.
• the scopes can also be manually cleaned, disinfected in an AER cycle and stored in a drying cabinet.
• Plasma treatment can be applied to the stored scopes on demand in a drying cabinet, e.g., prior to patient use to kill any biofilm that may be growing due to improper storage conditions or in the procedure room before use on a patient similar to flash sterilization.
• Plasma disinfection according to the presently disclosed system and method has also been shown to be effective up to a distance of 6 feet from the source of the plasma, which would accommodate a majority of the endoscopes available on the market today.
• Plasma disinfection is an on-demand point-of-use disinfection system that is portable and scalable to allow for the treatment of multiple endoscopes at one time.
• Pseudomonas aeruginosa ATCC 15442 was subcultured on Tryptic Soy Agar (TSA) plates and incubated at 37°C for 16 to 18 hours, A single colony was isolated from a streak plate and used to inoculate 10 mL of Tryptic Soy Broth bacterial growth media. A culture was grown at 37°C for 16 to 18 hours. Viable bacterial density was determined by a ten-fold serial dilution which was plated for enumeration. This was used as the inoculum solution to initiate biofilm growth.
• TSA Tryptic Soy Agar
• the positive control PTFE tubing was cut into halves. One half was further cut into four 10 cm sections representing the ends and the middle of the lumen. Each tubing section was placed into a separate sterile Falcon tube containing 15 mL of phosphate buffered saline. The samples were sonicated for 20 minutes at 25°C. The sonicated samples were vortexed and a tenfold serial dilution was made of the PBST used to sonicate each tubing section by transferring 1 mL of the liquid to a sterile conical vial containing 9 mL buffered water.
• a sterilization system generally as described in FIG. 1, and having a plasma generator generally as described in FIG. 2B was provided. More specifically, the plasma generator was constructed by feeding parallel electrodes composed of two strands of 3M Color Coded Flat Cable 3302, commercially available from 3M Company (St. Paul, MN) into PTFE tubing having an lumen 3/16 inch (4.76 mm) in inside diameter. The anode and cathode were separated on a PVC backing at a 0.05 inch (1.27 cm) center-to-center spacing.
• DC pulsed power was supplied by a power supply commercially available as FPG 50- 1NM from FID GmbH (Burbach, Germany). The power was set to provide a rectangular pulse with a pulse width of 10 nanoseconds and a variable pulse repetition rate and a variable voltage. Power measurements were taken with a homemade E-dot and B-dot probe.
• the flow rate of compressed air or a nitrogen/oxygen mixture into the was controlled using an MKS mass flow controller commercially available from MKS Instruments of Andover, MD.
• the gas was humidified through a bubbling unit before being transported to the plasma generator.
• the plasma byproducts were further transported through connected tubing in order to measure the downstream response.
• the PTFE biofilm tubes contained rinse liquid, which was subsequently blown out of the lumen once the plasma treatment was initiated. This liquid is recorded as the "flow though sample,” and was evaluated by vacuum filtration to determine if any bacteria could be recovered. No bacteria were present in the "flow through sample.” [0078] After plasma treatment, the PTFE tubing was flushed with PBST (1ml x 4) to remove any remaining bacteria which was subsequently recovered by vacuum filtration.
• the following Examples describe a plasma disinfection method useful to achieve microbial kill of biofilm found in washed but undried lumened medical devices such as endoscopes.
• the Examples show effective kill of four different microorganisms in liquid droplets using two models (10 wells and 5.80 mm ID lumens) treated using a remote plasma treatment system and method.
• These Examples demonstrate disinfection-level kill (>6 logio) using models that mimic the conditions and residual droplets encountered in the channels of a washed flexible endoscope.
• This remote plasma system and method is effective at killing microorganisms at a distance of 10 feet ( ⁇ 3 m) away from the plasma source using an extremely short treatment cycle (e.g. , 60 - 150 seconds).
• TSA Individual streak plates
• E. coli, P. aeruginosa, S. aureus, and E. faecalis were prepared from freezer stocks and incubated for 24 hours at 37°C.
• a single colony from each plate was used to inoculate 10 mL of TSB growth medium to culture each organism overnight (16-18 hours) with shaking at 250 RPM at 37°C.
• Each overnight culture reached a concentration ⁇ 10 9 colony forming units per milliliter (CFU/mL) and was diluted 1 : 10 in Butterfield's Buffer to create a solution containing ⁇ 10 8 CFU/mL used to inoculate samples for plasma treatment.
• a plasma disinfection system generally as described in FIG. 1, and having a plasma generator generally as described in FIG. 2A was utilized in examples 7 and 8.
• the ozone generator tube available from Ozonefac Co. (Guangzhou, Guangdong, China) as part of the CT-AQ8G ozone machine was utilized as the plasma electrode.
• Power was coupled to the plasma electrode from 12 kHz ac power supply with a voltage of 3.6 kV and a total power of 85 W.
• Plasma disinfection was achieved by transporting the gas output from the plasma through a 10-foot ( ⁇ 3 m) length of FEP tubing with an inner diameter of 1/8 inch ( ⁇ 3.2 mm). Samples were inserted at the end of the 10-foot ( ⁇ 3 m) tube. The gas output from the remote plasma generator was flowing at a rate of 3 L/min, and the gas was selected to be 1,000 standard cm 3 /min (SCCM) of moist air and 2000 SCCM of dry air. The relative humidity during all disinfection treatments ranged between 40-60%.
• SCCM standard cm 3 /min
• the disinfection treatment cycle for the SRBI wells described in Example 7 consisted of a 150 second plasma exposure followed by a 60 second air flush.
• Plasma treatments in the Lumen Model ranged from 0 - 150 seconds followed by a 60 second air flush.
• 3M SRBI nanosilica primed wells were cut from a roll of the film into individual strips using a standard paper cutter. Each strip contained eight wells capable of holding 10 of liquid between the two edges. The strips were cleaned by wiping with 70% isopropyl alcohol and dried prior to use. For each experiment, ⁇ 10 6 microorganisms were loaded into wells in positions 1 and 8 by pipetting 10 of a bacterial suspension containing ⁇ 10 8 CFU/mL prepared for each organism (E. coli, P. aeruginosa, S. aureus and E. faecalis) as described in the Bacterial Culture section.
• strips containing the microbial samples were loaded into the 1 foot removable section 6.35 mm outer diameter (OD)/5.80 mm inner diameter (ID) PTFE tubing using sterile tweezers and either treated with a plasma cycle of 150 seconds + 60 seconds of air or 210 seconds of air (positive controls).
• the wells containing the 10 samples were cut off from the rest of the strip using sterile dissecting scissors and transferred to individual 1.5-mL tubes containing 1 mL of PBS-TWEEN with sterile tweezers. Each tube was vortex-mixed at maximum speed for 1 minute and serial dilutions were made in Butterfield's Buffer, which were plated on PETRIFILM AEROBIC COUNT plates through the 10 "7 dilution for each sample.
• Inoculated plates were incubated for 24-48 hours at 37 °C and counted using a 3M PETRIFILM READER.
• the 1 minute vortex-mixing in PBS-TWEEN was validated by comparing recovery to enumeration controls (direct serial dilutions of the 10 inoculum into Butterfield's Buffer instead of the SRBI well; see Table 11), thereby confirming that this method recovered all of the microorganisms deposited in the SRBI well.
• n 6.
• the inoculated lumens were then attached to the plasma treatment set up as described in the Plasma Exposure section above. Each removable section of tubing was sequentially connected to the 10-foot ( ⁇ 3 m) piece. A time-course experiment was conducted with duplicate samples exposed to a plasma disinfection treatment cycle of 0 seconds, 15 seconds, 30 seconds, 60 seconds, 90 seconds, 120 seconds and 150 seconds, with each plasma exposure followed by a 60 second air flush.
• each lumen was cut in half to create two 3-inch (-7.62 cm) sections using a razor blade freshly cleaned with isopropyl alcohol and transferred to a 15-mL conical vial containing 10 mL of PBS-TWEEN. Any remaining viable bacteria were then recovered from each lumen by vortex-mixing the vial at maximum speed for 1 minute, disrupting with 2 x 20 second duration pulses at 20 kHz with a probe sonicator set at 39% of the maximum amplitude, then vortex-mixing again for 1 minute at maximum speed.
• PETRIFILM AEROBIC COUNT plates through the 10 "7 dilution for each sample (with the original 10 mL recovery solution being the 10 "1 dilution). The inoculated plates were incubated for 24-48 hours at 37°C and counted using a 3M PETRIFILM READER. This lumen test procedure was adapted from the American Society for Testing and Materials International (ASTM) method E1837 - Standard Test Method to Determine Efficacy of Disinfection Processes for Reusable Medical Devices (Simulated Use Test).
• ASTM American Society for Testing and Materials International
• a kill curve in a 5.80 mm ID PTFE lumen model based on ASTM E1837 was generated by exposing duplicate samples incubated with P. aeruginosa suspensions to plasma cycles of varying exposure time from 0 second - 150 seconds. Each lumen contained droplets ranging from -5-50 when plasma treatment was initiated. Visible droplets remained in the lumen after plasma exposure, but the amount of residual liquid was not quantified. Recovery of any remaining viable bacteria after the plasma cycle showed the complete kill (7.6-logio) was achieved within 60 seconds of plasma treatment (Table 13).
• Table 13 Survival of P. aeruginosa in a 5.80 mm ID Lumen over Time.

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