Sterilization: What is it?

Any procedure that eliminates, destroys, or deactivates all life is called sterilization. The word “sterile,” which denotes the total absence of live microorganisms or microbes with the capacity to proliferate, is associated with sterilization. As a result, after being put in their final packing, sterile products that go through sterilization are frequently thermally or chemically sterilized. Any bacteria found within the products (obtained during manufacture and packaging) are eliminated by chemical or heat sterilization. Terminal sterilization is the process of sterilizing a product using heat or chemicals after it has been packaged.

What is moist heat sterilization?

Steam sterilization is another name for sterilization by wet heat. Using steam under pressure, moist heat sterilization eliminates microorganisms in a product. The most used technique for sterilizing medical devices and products is moist heat sterilization.

What things may wet heat sterilize?

Rubber, sturdy plastics, mixing tanks, surgical instruments, filling tools, freeze-dryer chambers, and full product containers that can tolerate exposure to high temperatures are among the items that are typically sterilized by moist heat.

How is moist heat sterilization carried out?

To put it simply, steam under pressure is used to sterilize using moist heat. Autoclaves, which are pressurized vessels, are the most often used devices for moist heat sterilization. Pure steam devoid of air or other non-condensable gases is required for wet heat sterilization. The primary function of autoclaves is to eliminate air from the chamber and substitute it with pure, saturated steam. For steam sterilization to work, air must be eliminated. The presence of moisture (steam) to displace air, the type of air removal mechanism (such as vacuum), the design of the load being sterilized, and the absence of air leaks in the autoclave all affect how well air is removed.

Temperature is monitored via thermocouples in autoclaves. Indicators such as Bowie-Dick or Dart confirm that the temperature being recorded is steam heat rather than dry heat. When sufficient steam penetration has taken place, dark brown stripes start to emerge over the Bowie-Dick tape. Temperature, pressure, and biological indications are additional markers for verifying the sterilization of wet heat sterilization procedures.

Microorganisms’ lethality is dependent upon:

• Level of exposure to heat
• The length of time spent in the heat
• Level of moisture

By denaturing the proteins inside the cells, heat-based sterilizing techniques destroy bacteria. Saturated steam that comes into contact with a surface that is colder than itself will raise the surface temperature and release heat of condensation during the water’s phase transition from gas to liquid in moist heat sterilization. Any germs in the area where the steam penetrates are killed by the hundreds of calories of energy released by the heat of condensation. An item cannot be properly sterilized by moist heat if moisture cannot get to it, such as with oil.

Three phases make up the standard steam sterilization cycle:

• Preconditioning the chamber and its contents to exclude air and substitute it with saturated steam
• The sterilizing cycle that was selected
• Pressure is released and steam is removed

By increasing 15 pounds per square inch of pressure above atmospheric pressure, the boiling point of water is raised from 100°C to 121°C in order to produce steam. The ability of the steam to completely enter the items being sterilized is essential to the steam sterilization cycle. For solution sterilization, the temperature of the solution must be raised to the point where microbial proteins are denatured by heating the container walls. There must be a certain amount of moisture within any covered or sealed container. Otherwise, the interior of the container won’t be properly sanitized and steam won’t be able to enter. Glass containers are utilized for steam-sterilized liquids since plastic syringes or containers can rupture under pressure.

Which kind of autoclave is best for your product or medical device?

The many autoclave designs that are in use are numerous. The post-sterilization phase is carried out differently in each. Air replaces steam during the depressurization step known as post-sterilization. The following describes some examples of these different autoclave designs.

Vacuum-equipped autoclave with time-controlled vacuum maintenance

Following the completion of the sterilization cycle, the product load is vacuum-purged and allowed to cool. Both porous and nonporous solid materials are autoclaved employing time-controlled vacuum maintenance.

autoclave with cold water running through the jacket

This type of autoclave removes steam while introducing compressed sterile air. In order to keep solutions from boiling, compressed air is injected at pressures equivalent to the sterilizing pressure. with order to aid with cooling, this autoclave also circulates cold water inside its jacket. This kind of autoclave is used to sterilize liquids, including culture media.

Nebulized spray water autoclave

These autoclaves quickly condense steam and lower pressure by spraying the sterilized load with nebulized cool water after the sterilization cycle. This kind of autoclave is frequently used to sterilize plastic containers and glass-sealed ampoules.

Superheated water spray autoclave (water cascade)

Flexible containers that cannot withstand abrupt changes in both temperature and pressure are sterilized using this autoclave. No air is expelled from the chamber at the start of the water cascade autoclave sterilizing procedure. Rather, water is sprayed onto the load after being circulated in a heat exchanger. This procedure reduces sterilizing time by providing great temperature uniformity. To replace the steam and cool the load, cold tap water enters the heat exchanger’s plates. To prevent temperature or pressure shock, the autoclave chamber’s sterile air counter-pressure is constantly maintained. The containers cannot be dried during the cycle by this kind of autoclave.

Autoclave with Counter-Pressure Air Over Steam

Water cascade autoclaves and counter pressure autoclaves are comparable. One advantage of counter-pressure autoclaves is the ability to dry containers while the cycle is running. The cooling step takes a lot longer than with water cascade autoclaves, which is a drawback. Similar to water cascade systems, the chamber’s air is left in place prior to the cycle. Compared to traditional saturated steam autoclaves, this autoclave’s internal pressure is significantly higher. Throughout the autoclave operation, fans and flow deflectors in the chamber are used to control the partial air pressure of the air and steam, ensuring a uniform mixing of air and steam. In order to condense the steam and preserve the sterilizing phase pressure, air is fed into the chamber during the cooling phase.

• In-Place Sterilization (SIP)
• Large equipment items, mixing tanks, vessel-filter-filler systems, and isolator units are all sterilized using SIP.
• Equipment needed for a successful SIP must be able to withstand the pressures needed for steam sterilization.
• Use microbiological retentive filters to provide proper air ventilation.
• Condensate trap
• Avoid leaks
• possess no interior surfaces that aren’t steam-exposed.

What issues exist with wet heat sterilization?

The fundamental issue with moist heat sterilization is that not everything can withstand the pressure of steam without losing its integrity. Therefore, not all objects can be sterilized using moist heat, particularly those that contain electronics or flexible polymers. Additionally, because steam cannot reach oils or enclosed dry systems, moist heat cannot properly terminally disinfect them.

In Brief

The most affordable and widely used sterilizing technique is wet heat sterilization. Microbes are killed via moist heat sterilization, which exposes them to pressurized steam. The overkill method is frequently used in sterilization validations for moist heat sterilization. Overall, make sure the contract testing company you select can offer the right sterilizing validations for your product requirements.