Sterilisation wrap

These products are used to wrap and pack surgical instruments ready for sterilisation ahead of theatre use. Traditionally, the market used paper-based sterilisation wraps, either crepe or plain MG (INDA, Association of the Nonwoven Fabrics Industry) papers. Some parts of the market are now transitioning towards SSMMSS (SSMMSS is a composite of spunbond and meltblown nonwoven proceses) polypropylene composite materials [7]. 

Sterilisation Wrap www.amcor.com/businesses/healthcare/hospital packaging/business afhc hosp sheets.html, www.kcprofessional.com/us/product-details.asp prd id=10709, www.medicaldevice-network.com/features/feature80279/,www.plusmedical.cn/home. 

Humidity can be a problem. Whereas it was shown (284) that 33% RH was best for spore inactivation, and that at least 30% RH was needed for effective sterilisation (285), dried spores are difficult to kill, and the spore substrate material and wrappings compete with the spore for the available moisture (286). Therefore, the relative humidity is adjusted to 50—70% to provide sufficient moisture for the spores to equiUbrate. The exposure time depends upon the gas mixture, the concentration of ethylene oxide, the load to be sterilised, the level of contamination, and the spore reduction assurance requited. It may be anywhere from 4—24 hours. In a mn, cycles of pre-conditioning and humidification, gassing, exposure, evacuation, and air washing (Fig. 9) are automatically controlled. 

There are several ways to handle Petri dishes. The standard dishes are 15-20 mm deep and 12-15 cm in diameter. They are normally available in glass and also transparent plastic. Petri dishes are individually wrapped. The media is separately sterilised while we add the sterilised media to the Petri dishes in front of a flame. It is recommended to use 20-25 ml... 

Dry heat sterilisation is used for equipment that can withstand high temperature and dry heat but cannot withstand wet or steam autoclave. This method is often used for glassware as it dries and sterilises in one operation. The pipets must be wrapped in dustproof aluminum foil or placed in metal pipette cans. The can lids are removed during heating and replaced after sterilisation, that is before any dust can get in the can. Disposable items are not recommended for dry heat sterilisation. This method may only be good for permanent reusable glass pipettes. 

Normal laboratory glassware must first be washed and cleaned. It has to be rinsed with deionised water. The clean glassware is sterilised in an oven set at 200 °C for 1 1 hours. It is suitable to cover glassware with aluminum foil to maintain aseptic conditions after removing the glassware from the oven. If aluminum foil is not available, special heat-resistant wrap paper can be used. The sterile glassware must be protected from the air, which has micro-flora, or any contaminants. Avoid the use of any plastic caps and papers. Detach any labelling tape or other flammable materials, as they are fire hazards. 

Refrigerator parts, packaging, structural housing panels, pipe, defroster and heater ducts, sterilisable household items and hospital equipment, hoops, battery parts, blow moulded containers, including automotive petrol tanks, film wrapping materials, wire cable and insulation and chemical-resistant pipe. 

Cells may be grown in dishes or flasks where the initial inoculum varies from 0.2 X 106 up to 2 X 106. The containers may be glass or plastic. The plastic ware is obtained in sterile wraps from commercial suppliers and is specially prepared for use in cell culture (Fig. 3.2a) (see Appendix 3). The glass bottles are usually medical flat bottles but any bottle with a flat side will do provided it is washed correctly and sterilised before use (see Chapter 8). To a large extent the disposable plastic flask has now replaced the glass bottle. 

Fig. 3.6. Spinner flasks. The flask on the stirrer is protected from excessive heat by a layer of foam insulation. The vessel on the right is wrapped in aluminium foil for sterilisation. The model with the solid spindle which is allowed to swivel top and bottom is preferable to the one with metal swivel (on the left) as the latter tends to stir...

Resuspend the cells in prewarmed growth medium and filter through muslin or cheesecloth (filter funnels with muslin held in place with autoclave tape can be wrapped in aluminium foil or Kraft paper and sterilised by autoclaving). 

To sterilise small items such as rubber bungs they should be placed in glass Petri dishes and wrapped in aluminium foil. 

To obtain sterile gauze for filtering trypsinised suspensions when setting up primary cells the gauze is best arranged in a filter funnel and the whole wrapped in aluminium foil so that it can be unwrapped without contamination. Such wrapped funnels are sterilised by autoclaving. 

The methods of preparation of glassware are indicated in Chapter 8, and if sterilisation is monitored as described the glassware should not be a source of contamination. Likewise plasticware is obtained from the manufacturer in a sterile condition. Usually sterilisation of plastic is achieved using ethylene oxide or irradiation procedures and vessels are supplied wrapped in cellophane. 

Similar reactions are involved with the organotin stablilisers in PVC wrapping film when food is sterilised by y-irradiation.57... 

The items to be sterilised, other than products in sealed containers, should be wrapped in a material which allows removal of air and penetration of steam but which prevents recontamination after sterilisation. All parts of the load should be in contact with the sterilising agent at the required temperature for the required time. 

It is preferable for articles sterilised before use in the cleanroom to enter only via double-ended sterilisers sealed into the wall. Equipment to be sterilised for use in the cleanroom, such as filtration or sealing apparatus or hoses should be wrapped in a material which with normal handling does not permit recontamination after sterilisation. 

Thermally stable material such as glassware or metal instruments may be sterilised by heating them in an oven at 185°C for two hours. The material is wrapped in autoclave paper prior to heating, and after removal remains sterile until the wrapping paper is removed. Steam treatment in an autoclave is normally used for the sterilisation of aqueous material. The autoclave uses steam at a pressure greater than atmospheric and laboratory systems normally operate at 15 lbs in which corresponds to a temperature of 121 °C. This makes the assumption that the atmosphere inside the autoclave is composed only of steam and therefore it is necessary to expel all the air before the sterilisation process commences. 

The packaging of medical devices after cleaning and before sterilisation should protect the content (against contamination) as well as (during sterilisation) allow for removal of air and penetration of steam. The classical and most often used packaging material is sterlisation paper. Instrumentation kits are wrapped in sheets of sterilisation paper or non-woven materials that are subsequently sealed with sterilisation tape, which usually has a sterilisation indicator. 

The materials that need to be sterilised can be cleaned in the usual way. The packaging materials should be non-adsorbent to hydrogen peroxide. Therefore, plastics such as polyethylene and polypropylene are used instead of paper for wrapping the load. 

Remove the outer layer of the wrapped, sterilised disposable equipment and place them in the grade A zone or on the sterile area . 

The wraps have to be suitable for steam, EtO and gamma sterilisation. Specifically, wraps have to meet the requirements of BS EN 868 Part 2 and ISO 11607 Part 1. 

Since I consider sterilisation by irradiation a very suitable method there seems no point in using ethylene oxide which must surely be soluble in this plastic. Ethylene oxide freely penetrates two layers of low density polyethylene 250 micron thick and until proved otherwise, I think one has to accept that it will be very soluble in high density polyethylene. I fail to see how one can be sure of getting out all the ethylene oxide when double wrapped, even with the precautions mentioned in this letter. 

---