Sterilization methods and apparatus which employ additive-containing supercritical carbon dioxide sterilant

• US 20050025667A1
• Filed: 06/17/2004
• Published: 02/03/2005
• Est. Priority Date: 06/23/2003
• Status: Active Grant

• Current Assignee: NovaSterilis, Inc.
• Original Assignee: NovaSterilis, Inc.
• Inventors: Christensen, Timothy Wayne, Burns, David Carroll, Eisenhut, Anthony Romey, Ganem, Bruce, White, Angela Lydia
• Granted Patent: US 7,108,832 B2
• Time in Patent Office: Days
• US Class Current: 422/33
• CPC Class Codes: A61L 2/0088 Liquid substances
• CPC Class Codes: A61L 2/0094 Gaseous substances
• CPC Class Codes: A61L 2/186 Peroxide solutions
• CPC Class Codes: A61L 2/24 Apparatus using programmed or automatic operation
• CPC Class Codes: A61L 2202/24 Medical instruments, e.g. endoscopes, catheters, sharps

Abstract

Sterilization methods and apparatus are effective to achieve a 6-log reduction in CFUs of industry standard bacteria and bacterial spores, i.e., B. stearothermophilus and B. subtilis spores, by subjecting sterilizable materials to a chemical additive-containing carbon dioxide sterilant fluid at or near its supercritical pressure and temperature conditions. Most preferably, the chemical additive-containing supercritical carbon dioxide sterilant fluid is agitated during sterilization, e.g., via mechanical agitation or via pressure cycling.

Claims

1. A sterilization method comprising (a) bringing a material in need of sterilization into contact with a sterilant fluid comprised of carbon dioxide at or near its supercritical pressure and temperature conditions, and a sterilization enhancing effective amount of a chemical sterilization additive, and (b) maintaining said contact with the sterilant fluid under said temperature and pressure conditions for a time sufficient to achieve a 6-log reduction or greater in colony forming units (CFUs).

2. The sterilization method of claim 1, which comprises agitating the sterilant fluid.

3. The sterilization method of claim 2, wherein said step of agitating the sterilant fluid is practiced by subjecting the sterilant fluid to mechanical agitation or by cycling the pressure of the sterilant fluid between at least two different pressure conditions.

4. The sterilization method of claim 1, wherein the chemical sterilization additive comprises a peroxide or a carboxylic acid.

5. The sterilization method of claim 4, wherein the chemical sterilization additive comprises an alkanecarboxylic acid and/or an ialkanepercarboxylic acid, each of which may optionally include one or more electron-withdrawing group selected from halogen oxygen or nitrogen groups substituted at the alpha carbon thereof.

6. The sterilization method of claim 1, wherein the chemical sterilization additive comprises at least one selected from the group consisting of hydrogen peroxide, acetic acid, peracetic acid and trifluoroacetic acid.

7. The sterilization method of claim 1, wherein the chemical sterilization additive comprises a mixture of acetic acid, hydrogen peroxide and peracetic acid.

8. The sterilization method of any one of claims 1-7, wherein the sterilization additive is present in an amount of between about 0.001% to about 2.0% based on the total volume of the sterilant fluid.

9. A sterilant fluid which comprises carbon dioxide at or near its supercritical pressure and temperature conditions, and a sterilization enhancing effective amount of a chemical sterilization additive.

10. The sterilization method of claim 9, wherein the chemical sterilization additive comprises a peroxide or a carboxylic acid.

11. The sterilization method of claim 10, wherein the chemical sterilization additive comprises an alkanecarboxylic acid and/or an alkanepercarboxylic acid, each of which may optionally include one or more electron-withdrawing group selected from halogen oxygen or nitrogen groups substituted at the alpha carbon thereof.

12. The sterilant fluid of claim 9, wherein the chemical sterilization additive comprises at least one selected from the group consisting of hydrogen peroxide, acetic acid, peracetic acid and trifluoroacetic acid.

13. The sterilant fluid of claim 9, wherein the chemical sterilization additive comprises a mixture of acetic acid, hydrogen peroxide and peracetic acid.

14. The sterilant fluid of any one of claims 9-13, wherein the sterilization additive is present in an amount of between about 0.001% to about 2.0% based on the total volume of the sterilant fluid.

15. Apparatus for sterilizing an article in need of sterilization comprising:

a pressure vessel for containing the article in need of sterilization;

a source of supercritical carbon dioxide connected to the pressure vessel;

a source of a liquid chemical sterilization additive connected operatively to the pressure vessel;

means for introducing the supercritical carbon dioxide and sterilization additive to the pressure vessel; and

a depressurization line fluid-connected to the pressure vessel for evacuating at least some portion of the carbon dioxide and sterilization additive from the pressure vessel so as to depressurize the same.

16. Apparatus as in claim 15, further comprising a liquid-gas separator in said depressurization line for separating carbon dioxide gas from the liquid sterilization additive.

17. Apparatus as in claim 15 or 16, further comprising a valve in said evacuation line to allow said at least some portion of the carbon dioxide and sterilization additive to be evacuated from the pressure vessel through the depressurization line.

18. Apparatus as in claim 15, further comprising agitation means for agitating the carbon dioxide and sterilization additive within the pressure vessel.

19. Apparatus as in claim 18, wherein said agitation means comprises means for periodically changing pressure conditions within the pressure vessel.

20. Apparatus as in claim 18, wherein said agitation means comprises a stirrer for mechanically stirring the carbon dioxide and sterilization additive within the pressure vessel.