HK1147960B - Sterilisation indicator - Google Patents

Abstract

The invention relates to a sterilisation indicator (17) characterised in that it comprises: a compound (21) that heats up upon contact with oxygen (O) and/or nitrogen (N) atoms, and a thermochromic dye (19) which is in thermal contact with the compound (21).

Description

Sterilization indicator

The present invention relates to a sterilization indicator, in particular for use in sterilizing medical or surgical instruments by post-discharge (post-discharge) plasma obtained from nitrogen and/or oxygen based gases, in particular for use in dental applications.

Sterilization refers to the destruction of a given proportion of microorganisms, viruses, or pathogenic proteins present on the internal and external surfaces of an article to be sterilized.

It should be noted that the adjective "sterile" is an absolute term, but ensuring that the item is sterile, i.e. free of microorganisms, is a probability function. The Sterility Assurance Level (SAL) of an article is defined as the probability that any given unit will have microorganisms present after an effective sterilization process. Thus, for an item to be considered sterile with reference to the european standard EN556, it must have 10^-6SAL of (A), i.e.the theoretical probability of isolating the microorganism, must be less than 10⁶And one-fourth.

Various sterilization processes are known, including chemical processes and physical processes.

Among the chemical sterilization processes, there may be mentioned processes using a gas such as ethylene oxide (ethylene oxide), formaldehyde (formaldehide), or hydrogen peroxide (hydrogen peroxide). However, these processes still suffer from the drawback of requiring a long desorption time, which is incompatible with the rapid acquisition of sterilized instruments. In addition, these gases are toxic and irritate the skin and mucous membranes.

The physical processes include in particular steam sterilization in an autoclave by the action of temperature and steam; dry heat sterilization; irradiation with ion beams or gamma rays for articles that cannot be sterilized by heat or chemical means; or filtration using a filter suitable for separating out microorganisms. These processes typically involve high temperatures, often in excess of 100 ℃.

Since temperature sensitive materials, such as polymeric materials, are increasingly used in medical applications, it is desirable to develop a sterilization process that can be performed at low temperatures, particularly below 70 ℃.

A sterilization process using plasma has therefore been developed which operates at temperatures that avoid damage to temperature sensitive materials.

For example, application WO 00/72889 discloses a sterilization process using a plasma based on oxygen and nitrogen. Application FR 2856600 describes a sterilization process using a post-discharge plasma derived from a plasma consisting entirely of nitrogen, whereas application FR 2879933 uses a post-discharge plasma derived from a plasma consisting of hydrogen and nitrogen. Many sterilization processes therefore utilize nitrogen or oxygen based gases to prepare the plasma.

To verify the effectiveness of the sterilizer, a sterilization indicator is used that can monitor one or more necessary parameters in the sterilization process. To this end, three sterilization indicators have been developed: physical indicators, chemical indicators, and biological indicators.

Fewer sterilization indicators have been developed for processes utilizing plasma. Documents US 6659036, WO 98/46279, JP 2005111154 and JP 2004298479 disclose sterilization indicators relating to processes using plasma. However, these documents do not relate to nitrogen and/or oxygen based plasmas.

Therefore, there is a need for a method for utilizing nitrogen N from the group consisting of₂And/or oxygen O₂A post-discharge (post-discharge) plasma obtained in the gas of (a) capable of evaluating at least one parameter of a sterilization process.

Applicants have developed a sterilization indicator that achieves the above-noted goals. In particular, the indicator of the present invention may indicate the presence of oxygen atoms O and/or nitrogen atoms N in the post-discharge plasma.

The sterilization indicator for use in a sterilization apparatus according to the present invention comprises:

composition comprising a metal oxide and a metal oxideWhich, when brought into contact with oxygen atoms O and/or nitrogen atoms N, release heat, in particular from a gas comprising oxygen atoms O₂And/or nitrogen N₂Oxygen atoms O and/or nitrogen atoms N present in the post-discharge plasma obtained in the gas of (a); and

a thermo-sensitive dye (thermo-chemical dye) in thermal contact with the composition.

The term "in thermal contact with the composition" as used herein means that the dye is placed relative to the composition in such a manner that the exotherm of the composition results in an increase in the temperature of the dye.

In order to ensure a large contact area between the composition and the dye, thereby enhancing heat exchange, the composition is preferably in the form of a powder, granules, filaments, or fibers.

The composition preferably comprises at least one metal. The surface recombination of nitrogen atoms N or hydrogen atoms H is enhanced by the presence of the metal surface, which recombination is exothermic. On the metal surface, the atomic recombination probability of nitrogen atoms N or oxygen atoms O is high. Since the reaction is exothermic, the energy of the recombination reaction is partially transferred to the metal.

The metal of the composition may be selected from copper, titanium, steel, aluminum, or alloys thereof.

Copper and its alloys are preferably used.

The heat sensitive dye may be reversible or irreversible. A heat-sensitive dye is a dye that changes color under the influence of temperature. The heat-sensitive dyes are irreversible when the colour obtained under the effect of the temperature is permanent and cannot recover its initial colour.

The reversible or irreversible nature of the thermosensitive dye is selected according to the use to which the indicator is directed. Reversible thermosensitive dyes may be used if it is desired to track the color change of the dye in real time and to reuse the dye immediately after sterilization. Conversely, if the indicator is to be stored with the item to be sterilized for subsequent sterilization parameter verification, an irreversible heat sensitive dye should be used.

The dye should be selected according to the nature of the composition and the parameters of the sterilization process. The temperature rise of the dye is a function of the exothermic capacity of the composition in contact with the nitrogen atoms N and/or the oxygen atoms O, or of the number of nitrogen atoms N and/or oxygen atoms O in contact with the composition.

The composition and the dye are preferably in contact with the medium, i.e. placed on and/or in the medium. The composition can thus be placed or dispersed on the medium in which the dye is located. The composition may also be placed in the medium, for example sprayed in the medium or interwoven in the medium by the form of fibers.

Any type of media, such as porous media, may be used to facilitate diffusion of the dye through the media.

The media may be in the form of a sheet (e.g., made of a polymer or metal), a fiber (e.g., metal, natural or chemical fibers), or a woven or non-woven fabric.

In particular, the medium may be selected from cellulose, fabric, fiber, cotton, paper, or blotting paper.

The present invention also provides a method of indicating the presence of oxygen atoms O and/or nitrogen atoms N in a plasma present in a post-discharge chamber (post-discharge plasma). The method advantageously uses oxygen O₂And/or nitrogen N₂Is achieved in a post-discharge chamber of the sterilization device of the plasma obtained in the gas. The method sequentially comprises the following steps:

contacting a sterilization indicator according to the present disclosure with a plasma; and

the color of the dye of the indicator is compared to a reference color.

The reference color is set as a function of the parameters used in the sterilization process.

Thus, by comparing the color of the dye after the process with a reference color, it can be observed whether the indicator of the present invention has encountered the desired number of nitrogen atoms N and/or oxygen atoms O. The exotherm of the composition and its temperature are proportional to the number of nitrogen atoms N and/or oxygen atoms O with which the composition is exposed. Since the temperature reached by the composition determines the colour of the dye, the colour observed is in fact related to the number of nitrogen atoms N and/or oxygen atoms O with which the composition has been exposed.

The color of the indicator of the present invention can be compared to a reference indicator either visually or by using an automatic comparator device, such as a spectrophotometer.

To define whether two colors are considered to be the same, the Kubelka-Munk equation and color change according to the CIE Lab model, which is a model developed by the international commission on illumination (CIE), representing colors may be utilized.

According to the Kubelka-Munk equation, the ratio of the absorption coefficient K of the dye to the scattering coefficient S of the dye is related to the reflection coefficient beta as follows:

K/S＝(1-β)²/(2β)

according to the CIE Lab model, the color difference between the two compositions 1 and 2 is expressed as follows:

in this equation, L^*Is the brightness, a^*Indicating position on the axis from magenta to green, b^*Indicating the position on the yellow to blue axis.

For the colors of two dyes to be considered the same, then one may require

In one embodiment, the indicator may also be used to indicate the temperature in the post-discharge chamber. In this case, it is appropriate to observe the colour of the dye when the indicator is placed in the post-discharge chamber at the start of the sterilization process. The contact with nitrogen and/or oxygen atoms results in an exotherm of the composition which is slower than the temperature dependent color change of the dye present in the post-discharge chamber.

In such an embodiment, the heat sensitive dye is preferably selected to exhibit at least two different colors, with the color gradually changing as the temperature is increased from ambient temperature (20 ℃) to the temperature to which the metal is heated.

Such dyes may in particular be dyes from the company Chemsong.

The present invention thus provides a method of indicating the following information: a) the presence of oxygen atoms O and/or nitrogen atoms N in the plasma present in the post-discharge chamber, possibly from the group comprising oxygen O₂And/or nitrogen N₂Obtained in the gas of (1); and b) the temperature in the post-discharge chamber.

The method sequentially comprises the following steps:

contacting a sterilization indicator according to the present disclosure with a plasma;

comparing the color of the dye of the indicator to a first reference color, the first reference color being representative of a reference temperature within the cavity; and

comparing the color of the dye of the indicator with a second reference color, said second reference color representing a reference number of oxygen atoms O and/or nitrogen atoms N.

In this way, the colour of the dye can be compared with the first reference colour at the start of sterilisation to ensure that the reference temperature in the post-discharge chamber has been reached. And comparing the colour of the dye with a second reference colour at the end of sterilization to ensure that a reference number of nitrogen atoms N and/or oxygen atoms O in contact with the indicator is reached during sterilization.

The present invention also provides a sterilization indicator that simplifies the testing of the temperature within the post-discharge chamber, while also testing for the presence of nitrogen atoms N and/or oxygen atoms O within the post-discharge chamber. The indicator includes:

a first part comprising a composition that is exothermic when in contact with an oxygen atom, O, and/or a nitrogen atom, N, and a heat-sensitive dye in thermal contact with the composition; and

a second part comprising a heat-sensitive dye and not comprising a composition which releases heat when in contact with an oxygen atom O and/or a nitrogen atom N.

The first part is the same as the above-mentioned indicator, and is used for checking the content of nitrogen atoms N and/or oxygen atoms O in the post-discharge plasma.

The second part includes a heat sensitive dye, but does not include an exothermic composition. The second portion of the sterilization indicator is used to verify the temperature within the post-discharge chamber (sterilization chamber). The dye is not in contact with the exothermic composition and is only affected by the temperature of the post-discharge chamber, without any other heat supply.

The dye of the second part of the indicator may be the same as the dye present in the first part.

Accordingly, the present invention provides a method of indicating the following information: a) the presence of oxygen atoms O and/or nitrogen atoms N in the plasma present in the post-discharge chamber, in particular from the group comprising oxygen O₂And/or nitrogen N₂Obtained in the gas of (1); and b) the temperature within the post-discharge chamber. The method sequentially comprises the following steps:

contacting the sterilization indicator with a plasma; and

the colors of the dyes of the first and second portions of the indicator are compared to two reference colors.

The color of the dye of the first part of the indicator may be compared to a first reference color, which represents a reference number of oxygen atoms O and/or nitrogen atoms N, and then the color of the dye of the second part of the indicator may be compared to a second reference color, which represents a reference temperature within the cavity. The colors of the two parts can also be compared with each other.

By using a two-part indicator, there is no longer a need to track changes in real time in the method.

Other objects, features and advantages of the present invention will be understood by reading the following description, given by way of example only, and with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation showing a sterilization apparatus having an indicator of the present invention;

FIG. 2 shows an indicator in a first embodiment of the invention; and

fig. 3 is a plan view of the indicator in the second embodiment.

The sterilization apparatus shown in fig. 1 comprises an inlet pipe 1 for nitrogen N through a vacuum enclosure 2₂The vacuum enclosure 2 is subjected to an electric field generated by a microwave generator 3 operating at 2.45 gigahertz (GHz). The electric field being specially adapted for forming electric fields originating from N₂The N atom of the molecule. The plasma generated in this way is conveyed into the sterilization chamber 4 through the tube 5 by means of the vacuum pump 6. The plasma is delivered to the chamber 4 through the nozzle 15. The nozzle 15 may advantageously terminate in one or more injectors for homogenizing the plasma stream. The vacuum pump 6 is also used to discharge the plasma to the outside through a pipe 7 provided with a filter 8.

The sterilization chamber 4 is referred to as a "post-discharge" chamber because the plasma is not subjected to the electric field therein, but rather to the field in the enclosure 2. The plasma present in the chamber 4, known as "post-discharge" plasma, is not affected by the electric field and therefore no longer contains Ultraviolet (UV) radiation, ions, or electrons, so that it is possible to avoid excessively raising the temperature in the chamber 4, which would damage the item 10 to be sterilized.

The sterilization chamber 4 is in the form of a rectangular parallelepiped comprising a metallic or non-metallic instrument holder 9 for accommodating the items 10 to be sterilized. The sterilization chamber 4 is equipped with a heater device 11 which delivers a temperature controlled by a control device 12. These heater means may in particular be constituted by resistive or inductive heater means.

The sterilization chamber 4 is closed on one side by a pivoting door 13.

The chamber 4 is also equipped with a reflector 14 and a fan 16 which facilitate the homogenization of the plasma.

The item to be sterilized 10 is placed in the chamber 4 with one or more sterilization indicators 17. The sterilization indicator 17 may extend over the cavity 4 and in particular may be located in a position that is difficult to reach, for example, against the walls of the cavity 4 or below the items 10 to be sterilized. In this way it is ensured that the entire volume of the sterilization chamber is treated with the plasma of nitrogen.

It is particularly useful to place the sterilization indicator 17 on or in the sterilization bag containing the item 10 to be sterilized to ensure that the item 10 itself is in contact with the nitrogen atom N.

The pressure in the sterilization chamber 4 is preferably less than 10⁵Pascal (Pa) to facilitate contact of nitrogen atom N with article 10.

Fig. 2 shows a sterilization indicator 17 of the present invention.

The sterilization indicator 17 includes a medium 18, the medium 18 being impregnated with a dye 19 that diffuses within the medium 18 to form a dye zone 20. A composition 21 in the form of a metal fiber is placed in the media and dye zone 20. As shown in fig. 2, the fibers are placed in the dye region 20, but it is also contemplated that the fibers may be dispersed throughout the media 18 to extend beyond the dye region 20.

Fig. 3 shows a two-part sterilization indicator 17 according to the present disclosure. The indicator 17 includes a first portion 22, the first portion 22 including a dye 19 that diffuses in the medium 18 to form a dye region 20. The composition 21 in the form of metal fibers is placed in a medium in the dye region 20.

In the second portion 23 of the indicator 17, which does not contain the composition 21, the dye 19 forms a dye region 24. The two dye areas 20 and 24 are sufficiently far apart that the metal fiber 21 is not in thermal contact with the dye area 24 of the second portion 23.

In the following two examples, the parameters of the sterilization process are as follows: the temperature in the sterilization chamber 4 was 60 ℃ and the flow rate of nitrogen gas was 1 liter per minute (L/min) at 6.66X 10²The time of exposure to the post-discharge plasma was 40 minutes using nitrogen gas at a pressure of Pa (5 Torr).

Further, the dye 19 used was Kromagen's magenta 120 screen printing ink dye (screen ink dye).

The color of the dye changes as a function of temperature:

20 ℃ of: white pink (tile white pink)

60 ℃ below zero: light pink colour

70 ℃ below zero: pink colour

90 ℃ C: magenta color

120 ℃ C: purple color

With the aid of different reference tests, it has been determined that the exothermicity of the metals in the indicators of examples 1 and 2 requires the dye to reach a temperature of 90 ℃ if the above parameters are followed.

Example 1: a portion of the sterilization indicator

The medium 18 is made of aramid fiber (meta-aramid fiber).

Composition 21 consisted of a copper nickel alloy wire having a diameter of 20 micrometers (μm) sold by the supplier Baltec Inc. under the name Monel. One method of making the indicator is to contact the filament 21 with the media 18 and then pour the dye 19 onto the media 18 and dry it at a temperature of 20 c. The indicator 17 thus produced exhibits a whitish pink color.

An indicator 17 is placed in the chamber 4, where it undergoes a sterilization process.

Dye 19 of indicator 17 is observed after 1 minute after sterilization. Its colour is light pink, indicating that the temperature inside the chamber 4 is about 60 ℃.

At the end of the process, the indicator 17 is magenta (dark pink), i.e. it has the desired color.

Example 2: two-part sterilization indicator

The media 18 is comprised of cotton fibers.

One method of making the indicator is to mix a 20 μm diameter copper wire with cotton fibers in a first portion 22 of the indicator 17 and then disperse the dye 19 onto the medium 18, including the first portion 22 and a second portion 23, to form two dye areas 20 and 24, which are then dried at a temperature of 20 ℃. The indicator 17 thus produced exhibits a whitish pink color.

At the end of the process, the dye region 24 is light pink, indicating that the temperature inside the chamber 4 is about 60 ℃. The dye region 20 is magenta (dark pink). The test is therefore valid.

The colour of the dye in contact with the metal is therefore determined taking into account the various parameters required to be used during the sterilization process, such as the concentration of nitrogen atoms N in the plasma, the duration of exposure of the article 10 to the plasma, the temperature in the sterilization chamber 4, and the volume of the article 10. The concentration of nitrogen atoms N can be selected by adjusting the power of the microwave generator 3 and the flow rate of nitrogen gas.

The determination of the colour of the dye also takes into account the characteristics of the metal 21, since the heat release from the metal surface is a function of the characteristics of the metal, and also takes into account the number of nitrogen atoms N in contact with the metal 21.

Thus, with the indicator 17 of the invention, it is possible to check two parameters of the sterilization process, namely the number of nitrogen atoms N and the sterilization temperature.

It can be determined that the sterilization assurance level of the process is a function of the pressure and flow rate of the nitrogen gas, the content of nitrogen atoms N, the temperature inside the sterilization chamber 4, and the sterilization duration. Since the concentration of nitrogen atoms N is proportional to the power of the microwave generator 3 at a given pressure and flow rate of nitrogen, the parameters used for verification are temperature, content of nitrogen atoms N, and duration of treatment.

The sterilization indicator 17 of the present invention is therefore particularly suitable for ensuring that the nitrogen atoms N present in the post-discharge plasma have actually come into contact with the entire sterilization chamber and the items 10 to be sterilized. Indicator 17 also acts to remove the compound from the composition comprising N₂And post-discharge plasmas obtained from gases of mixtures of other types, e.g. from N₂/H₂Or Ar/N₂The plasma obtained.

The indicator 17 also acts to remove oxygen from the mixture comprising O₂Oxygen atoms O present in the post-discharge plasma obtained in the gas of (2), e.g. from N₂/O₂Or Ar/O₂The plasma obtained.

Claims (13)

1. A sterilization indicator (17), characterized in that it comprises:

a first part (22) comprising a composition (21) that is exothermic when in contact with an oxygen atom O and/or a nitrogen atom N, and a first heat-sensitive dye (19) in thermal contact with the composition (21), the composition (21) comprising at least one metal, the color of the heat-sensitive dye being changed by the heat released when the composition (21) is in contact with an oxygen atom O and/or a nitrogen atom N; and

a second part (23) comprising a second heat-sensitive dye (19) and not comprising a composition (21) which exothermically releases on contact with an oxygen atom O and/or a nitrogen atom N.

2. An indicator (17) as claimed in claim 1, characterised in that the metal is selected from copper, titanium, steel, aluminium, or alloys thereof.

3. An indicator (17) as claimed in claim 2, characterised in that the metal is selected from copper or alloys thereof.

4. The indicator (17) according to any one of claims 1 to 3, characterised in that the composition (21) is in the form of a powder, granules or fibres.

5. The indicator (17) according to any one of claims 1 to 3, wherein the composition (21) and the dye (19) are in contact with a medium (18).

6. An indicator (17) as claimed in claim 5, characterised in that the medium (18) is in the form of a sheet or in the form of fibres.

7. An indicator (17) as claimed in claim 6, characterised in that the medium (18) is selected from the group consisting of cellulose, fabric, cotton, paper.

8. The indicator (17) according to any one of claims 1 to 3, characterised in that the dye (19) is an irreversible thermosensitive dye.

9. Use of an indicator (17) according to any of claims 1 to 8 in a sterilization device for sterilizing medical or surgical instruments by means of a post-discharge plasma obtained from a nitrogen and/or oxygen based gas.

10. Use according to claim 9 for indicating the presence of oxygen atoms O and/or nitrogen atoms N in a post-discharge plasma obtained from a nitrogen and/or oxygen based gas.

11. Use of an indicator (17) according to any of claims 1 to 8, further for indicating a temperature in a post-discharge chamber using a post-discharge plasma obtained from a nitrogen and/or oxygen based gas.

12. A method for indicating the presence of oxygen atoms O and/or nitrogen atoms N in a plasma present in a post-discharge chamber (4) using a post-discharge plasma obtained from a nitrogen and/or oxygen based gas, characterized in that it comprises, in sequence:

contacting the sterilization indicator (17) of any one of claims 1 to 8 with plasma; and

the colour of the dye (19) of the indicator (17) is compared with a reference colour.

13. A method of indicating the following information using a post-discharge plasma obtained from a nitrogen and/or oxygen based gas: a) the presence of oxygen atoms O and/or nitrogen atoms N in the plasma present in the post-discharge chamber (4); and b) the temperature in the post-discharge chamber, characterized in that the method comprises, in order:

contacting the sterilization indicator (17) of any one of claims 1 to 8 with plasma; and

the colours of the dyes (19) of the first and second portions (22, 23) of the indicator (17) are compared with two reference colours.