Patent Publication Number: US-2022212355-A1

Title: Isolator and method for sterilizing same

Description:
TECHNICAL FIELD 
     The present invention relates to an isolator to be used for cell preparation, and a method for sterilizing the same. 
     BACKGROUND ART 
     When cells or microorganisms are handled in research on pathogens, etc., regenerative medical treatments, etc. an isolator or a safety cabinet is to be used. 
     In the isolator that is a closed system, a worker can perform work via work gloves from the outside of an isolated work room. In the isolator, when a patient tissue to be handled is changed to another one or the type of a pathogen to be handled is changed, the sterilization of the inside of the work room or the work gloves by cleaning and disinfection is required. The sterilization is performed by supplying a sterilization gas to the work room or the gloves. 
     Patent Document 1 discloses one example of an isolator that supplies a sterilization substance, which has evaporated from a sterilization substance supply unit, to a work room to perform a sterilization process. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: JP 2010-69255 A 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the isolator that is a closed system, a sterility assurance level can be secured by sterilizing the work room or the work gloves by means of a supply of the sterilization gas thereto. Here, the sterility assurance level (SAL) refers to a maximum survival probability of contaminants estimated to exist in a sterilized product processed in a proper sterilization step, and is expressed by 10 −n . Currently, SAL 10 −6  is adopted internationally, and means that the survival probability of microorganisms in a sterilized object after a sterilization operation is one millionth. 
     Patent Document 1 describes the isolator that raises the temperature of a heater with the supply of the sterilization substance in parallel with a gas flow path leak test, to shorten the time required for the sterilization process; however, in Patent Document 1, shortening the time for a step for removing the sterilization substance (aeration step) is not taken into consideration. 
     An object of the present invention is to provide an isolator that is capable of improving work efficiency by shortening a sterilization time, and that is capable of securing a sterility assurance level. 
     Solutions to Problems 
     In order to solve the problem, according to one example of the present invention, there is provided an “isolator” in which a circulation fan above a work room supplies clean air to the work room via a HEPA filter, the isolator including: the work room; a front door provided in a front surface of the work room; a glove provided in the front door; and an air supply unit that causes an air supply HEPA filter to clean air taken in from an air supply airtight damper, and that causes an air supply fan to supply the clean air into the isolator, when work is performed. When a sterilization gas is removed, the air supply unit is configured such that the air supply fan circulates the air inside the isolator through a sterilization gas-removing catalyst. 
     In addition, according to one example of the present invention, there is provided a “method for sterilizing an isolator” including an air supply unit that cleans air taken in from an outside to supply the clean air into the isolator, and an exhaust unit that cleans air inside the isolator to exhaust the clean air to the outside, in which a circulation fan above an work room supplies the clean air to the work room via a HEPA filter when work is performed, the method including: a decontamination step of closing an air supply damper of the air supply unit and an exhaust damper of the exhaust unit, and supplying a sterilization gas into the isolator; and an aeration step of causing an air supply fan of the air supply unit to circulate the air inside the isolator through a sterilization gas-removing catalyst, causing an exhaust fan of the exhaust unit to circulate the air inside the isolator through a sterilization gas-removing catalyst, and removing the sterilization gas, after the decontamination step ends. 
     Effects of the Invention 
     According to the present invention, the sterilization time can be shortened, the work efficiency can be improved, and a sterility assurance level can be secured. 
     Tasks, configurations, and effects other than those described above become apparent from the description of the following embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view illustrating one example of an isolator of a first example. 
         FIG. 2  is a right central cross-sectional view of one example of the isolator of the first embodiment. 
         FIG. 3  is a plan view of one example of the isolator of the first embodiment. 
         FIG. 4  is a view illustrating a positional relationship between an exhaust unit and an air supply unit, and circulation fans of the isolator of the first embodiment. 
         FIG. 5  is a graph illustrating a change in the concentration of hydrogen peroxide gas in each step of a sterilization cycle. 
         FIG. 6  is a view illustrating a positional relationship between the exhaust unit and the air supply unit, and the circulation fans of an isolator of a second embodiment. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Embodiments of the present invention will be described with reference to the drawings. Incidentally, in the drawings for describing the embodiments, the same components will be denoted by the same names and reference signs as much as possible, and repeated descriptions thereof will be omitted. 
     First Embodiment 
       FIG. 1  is a front view illustrating one example of an isolator of a first embodiment,  FIG. 2  is a right central cross-sectional view thereof (cross-sectional view taken along line A-A in  FIG. 1 ), and  FIG. 3  is a plan view seen from above. 
     A work room  12  in which the work of handling specimens such as pathogens is to be performed is provided inside a case (housing). A front surface of the work room  12  is provided with a front door  14  covering an opening portion, and a lower portion of the front door  14  is provided with gloves  15  into which a worker can insert the hands to perform work. A circulation fan  16  is provided above the work room  12 , a circulation HEPA filter and a punching plate  19  are provided downstream of the circulation fan  16 , and clean straightened air is to be supplied to the work room  12 . A front slit (front suction port)  13   a  is provided on a front surface side of a lower portion of the work room  12 , and suctions air into the work room. In addition, air inside the work room is to be suctioned from a back slit (rear suction port)  13   b  provided on a back surface side. Air circulates in such a manner that the air suctioned through the slits  13   a  and  13   b  returns to an upstream side of the circulation fan  16  through ducts provided on side surfaces and back surfaces of the work room. An exhaust unit  20  is provided on an upper left side of the isolator, and a part of circulating air is to be fed to an exhaust HEPA filter  27  by an exhaust fan  26  and to be exhausted to the outside from an exhaust airtight damper  22  provided on an upper surface of the case. In addition, an air supply unit  40  is provided above right side portion of the isolator, an air supply HEPA filter  47  cleans air taken in from an air supply airtight damper  42 , and an air supply fan  46  supplies the clean air into the isolator. Here, the HEPA filter is an abbreviation for a high efficiency particulate air filter. 
     The front door  14  of the work room  12  is made of, for example, transparent glass or resin, and allows a worker to see work to be performed with the hands. In addition, the front door  14  is configured to be rotatable as indicated by an arrow in  FIG. 2  to be opened and closed. The front door  14  can be closed and sealed when work is performed, and can be opened during inputting of instruments and materials to allow the entry and exit of the instruments, etc. In the isolator of  FIG. 1 , two circulation fans  16 , two circulation HEPA filters  18 , etc. are provided in bilateral symmetry, but only one set may be provided. 
     The isolator includes a sterilization gas generation device to be used for sterilization, supplies a sterilization gas such as hydrogen peroxide gas to the work room  12  from a condition (outgoing) path  36  during a sterilization step, and sprays the sterilization gas from a sterilization gas inlet port  32 . The sterilization gas circulates through a flow path of the isolator, and a part of the sterilization gas returns to the sterilization gas generation device  30  through a condition (return) path  34 . 
     The isolator is provided with an aeration path for removing the sterilization gas after the sterilization step ends. As the aeration path, for example, as illustrated in the front view of  FIG. 1 , in the exhaust unit  20 , an exhaust H 2 O 2  catalyst unit  28  that absorbs the sterilization gas is provided in a blowout path of an exhaust fan  26 , and the exhaust airtight damper  22  is to be closed and a circulation airtight damper  24  is to be opened to allow the sterilization gas to circulate inside the safety cabinet. The exhaust H 2 O 2  catalyst unit  28  adsorbs the sterilization gas. In addition, in the air supply unit  40 , an air supply H 2 O 2  catalyst unit  48  is provided on a suction side of the air supply fan  46 , and the air supply airtight damper  57  is to be closed to allow the sterilization gas to circulate inside the isolator. The air supply H 2 O 2  catalyst unit  48  adsorbs the sterilization gas. 
     A sterilization process is to be performed roughly as follows (refer to  FIG. 5 ). 
     (1) Dehumidification Step 
     Humidity is to be lowered by dry air. The lowering of the humidity keeps the required concentration of a sterilization gas (for example, hydrogen peroxide gas) to a saturation level or less during the following conditioning step and the following decontamination step. Returning air passes through a dry cartridge to dried and heated. 
     (2) Conditioning Step 
     While a sterilization agent is injected into airstreams, the dry air continues to circulate until immediately before the sterilization gas leaves the isolator. The conditioning step is a step of causing the sterilization concentration to reach a target sterilization concentration rapidly. 
     (3) Decontamination Step 
     For a specified time, the sterilization agent causes the entire concentration of the sterilization gas inside the isolator to be maintained, and sterilizes the work room, the HEPA filter, etc. 
     (4) Aeration Step 
     The injection of the sterilization agent is to be stopped, and the airstreams circulate through the aeration path including the catalyst units that adsorb the sterilization gas. Then, the dry air is to be circulated for a certain time to lower the concentration of the sterilization gas inside the isolator and connection hoses. 
     An operation in the present embodiment will be described with reference to the drawing of  FIG. 4  illustrating a positional relationship between the exhaust unit and the air supply unit, and the circulation fans. 
     The exhaust unit  20  is provided on the upper left side of the isolator, and the exhaust unit  20  includes the exhaust fan  26 , the exhaust HEPA filter  27 , the exhaust airtight damper  22 , the exhaust H 2 O 2  catalyst unit  28 , and the circulation airtight damper  24 . When work is performed in the isolator, the circulation airtight damper  24  is closed, the exhaust airtight damper  22  is opened, a part of air circulating inside the isolator is to be fed to the exhaust HEPA filter  27  by the exhaust fan  26 , and cleaned air is to be exhausted to the outside from the exhaust airtight damper  22 . 
     During the sterilization process, the exhaust airtight damper  22  is to be closed, and the circulation airtight damper  24  is to be opened. Then, in the aeration step (step of removing a sterilization substance), the exhaust fan  26  circulates air containing the sterilization gas through the exhaust HEPA filter  27 , the exhaust H 2 O 2  catalyst unit  28 , and the circulation airtight damper  24 , and the sterilization gas is to be adsorbed on the exhaust H 2 O 2  catalyst unit  28 . As illustrated in  FIG. 4 , an outlet for the circulating air is disposed in an upper portion of a right circulation fan  16   b.  The circulating air is to be blown out to the upper portion of the right circulation fan  16   b,  and a part of the air and another part of the air are to be blown to the work room  12  from the right circulation fan  16   b  and from a left circulation fan  16   a,  respectively. 
     The air supply unit  40  is provided above the right side portion of the isolator, and the air supply unit  40  includes the air supply airtight damper  42 , the air supply fan  46 , the air supply HEPA filter  47 , and the air supply H 2 O 2  catalyst unit  48 . When work is performed in the isolator, the air supply airtight damper  42  is opened, the air supply HEPA filter cleans air taken in from the air supply airtight damper  47 , and the air supply fan  46  supplies the clean air into the isolator. 
     During the sterilization process, the air supply airtight damper  42  is to be closed. Then, in the aeration step (step of removing the sterilization substance), the air supply fan  46  circulates air containing the sterilization gas inside the isolator through the air supply HEPA filter  47  and the air supply H 2 O 2  catalyst unit  48 , and the sterilization gas is to be adsorbed on the air supply H 2 O 2  catalyst unit  48 . In this case, an air intake port  49  of a circulation path is provided in an upper portion of the duct provided on the side surface of the work room  12 , so that the sterilization gas in the air which has passed through the work room  12  can also be effectively removed. As illustrated in  FIG. 4 , the outlet for the circulating air is disposed in the upper portion of the right circulation fan  16   b . The circulating air is to be blown out to the upper portion of the right circulation fan  16   b,  and a part of the air and another part of the air are to be blown to the work room  12  from the right circulation fan  16   b  and the left circulation fan  16   a , respectively. 
       FIG. 5  illustrates a change in the concentration of hydrogen peroxide gas that is a sterilization gas in four steps of the sterilization process in the present invention and in the related art. The time for the aeration step is shortened in the present invention more significantly than in the related art. Here, in the related art, gas containing a sterilization gas in the gas flow path passes through a sterilization substance-removing filter of a gas exhaust unit once to be exhausted to the outside. In the case where the sterilization gas-removing catalyst and the exhaust HEPA filter are provided on a suction side of the exhaust fan and the sterilization gas is to be exhausted to the room, when high-concentration hydrogen peroxide gas passes through the catalyst during aeration, detoxification, for example, a reduction in concentration from 1,000 ppm to 1 ppm or less with one pass is required. For that reason, a large quantity of the catalysts is required, catalyst resistance increases, an aeration efficiency is poor, and the sterilization time is lengthened. In addition, electric power consumption increases, thereby resulting in high cost. In addition, when the sterilization gas passes through the catalysts only once, in a case where a catalyst function does not work or there are gaps between the catalysts, high-concentration sterilization gas leaks into the room, which is dangerous. 
     According to the present embodiment, since the circulation path is formed and the sterilization gas-removing catalysts are provided in the exhaust unit including the exhaust fan and in the air supply unit including the air supply fan, catalyst resistance can be reduced, the sterilization time can be shortened, and the work efficiency can be improved. In addition, since the air that has passed through the sterilization gas-removing catalysts is not exhausted to the outside of the room and only circulates inside the isolator, high-concentration hydrogen peroxide gas can be prevented from leaking to the outside of the isolator, and safety can be secured. 
     In addition, according to the present embodiment, since the disposition is such that low-concentration air which has passed through the catalyst of the air supply unit and the catalyst of the exhaust unit is to be suctioned to inlets of the circulation fans, the flow speed of the air can be increased, and the sterilization time can be significantly shortened. 
     Incidentally, in the present embodiment, the sterilization gas-removing catalysts are disposed in both the air supply unit and the exhaust unit, and air containing the sterilization gas circulates therethrough; however, the sterilization gas-removing catalyst may be disposed in only one thereof, and air containing the sterilization gas may circulate therethrough. In addition, the air supply units may be provided above the right side portion and above a left side portion of the isolator, a blowout port of the air supply unit disposed above the right side portion may be disposed near the inlet of the right circulation fan, and a blowout port of the air supply unit disposed on the left side portion may be disposed near the inlet of the left circulation fan. 
     Second Embodiment 
       FIG. 6  illustrates a positional relationship between the exhaust unit and the air supply unit, and the circulation fans of a second embodiment of the present invention. In the second embodiment, the size of the exhaust unit is reduced, a blowout port for air from the exhaust unit during aeration is disposed above the left circulation fan. 
     The exhaust unit  20  is provided on the upper left side of the isolator, and the exhaust unit  20  includes the exhaust fan  26 , the exhaust HEPA filter  27 , the exhaust airtight damper  22 , the exhaust H 2 O 2  catalyst unit  28 , and the circulation airtight damper  24 . 
     During the sterilization process, the exhaust airtight damper  22  is to be closed, and the circulation airtight damper  24  is to be opened. Then, in the aeration step (step of removing the sterilization substance), the exhaust fan  26  circulates air containing the sterilization gas through the exhaust HEPA filter  27  and the exhaust H 2 O 2  catalyst unit  28 , and the sterilization gas is to be adsorbed on the exhaust H 2 O 2  catalyst unit  28 . As illustrated in  FIG. 6 , the outlet for the circulating air is disposed in the upper portion of the left circulation fan  16   a , and the circulating air is to be taken into the left circulation fan  16   a  and to be fed to the work room  12 . 
     Meanwhile, the configuration of the air supply unit  40  is the same as that in the first embodiment, and the outlet for the circulating air is disposed in the upper portion of the right circulation fan  16   b,  and the circulating air is to be taken into the right circulation fan  16   b  and to be fed to the work room  12 . 
     According to the present embodiment, in the isolator including two right and left circulation fans, the blowout port of the air supply unit is provided above one circulation fan, and the blowout port of the exhaust unit is provided above the other circulation fan, so that low-concentration gas can be uniformly supplied to the work room, and the sterilization time can be shortened. 
     REFERENCE SIGNS LIST 
     
         
           10  Isolator 
           12  Work room 
           13   a  Front slit 
           13   b  Back slit 
           14  Front door 
           15  Glove 
           16  Circulation fan 
           18  Circulation HEPA filter 
           19  Punching plate 
           20  Exhaust unit 
           22  Exhaust airtight damper 
           24  Circulation airtight damper 
           26  Exhaust fan 
           27  Exhaust HEPA filter 
           28  Exhaust H 2 O 2  catalyst unit 
           30  Sterilization gas generation device 
           32  Sterilization gas inlet port 
           34  Condition (return) path 
           36  Condition (outgoing) path 
           40  Air supply unit 
           42  Air supply airtight damper 
           46  Air supply fan 
           47  Air supply HEPA filter 
           48  Air supply H 2 O 2  catalyst unit 
           49  Air intake port