Sterilization

Sterilization is a validated process that destroys, eliminates, or deactivates all forms of microorganisms (ie, bacteria, fungi, parasites, and viruses) along with the most resistant endospores and prions. Although both sterilization and disinfection remove pathogens, the key to distinguishing these two techniques is the endospore. After the complete sterilization process, an object is referred to as ascetic or sterile. Sterilization is commonly used in healthcare facilities (surgical and injectable devices), pharmaceutical industries (injectable medication and intravenous fluid), and food industries to protect against the contamination of Solar System bodies. Depending on the objectives and target materials, physical or chemical means of sterilization are commonly used. Among all the physical means, incineration is the most obvious form; however, it is not always practical, especially when the target object is reused or recycled. Therefore, the best alternative is the autoclave, a moist heat sterilization process typically done at high temperature and pressure (15 minutes at 121°C and 100 kPa). This is mainly used for glass, surgical instruments, and pre-treatment of medical wastes. Dry heat sterilization uses higher heat and more prolonged exposure to lethal temperatures (ie, two hours at 160°C) than moist heat sterilization. Nowadays, instead of flaming, microincineration is being used for inoculation loops and straight-wires sterilization due to the fire hazard. Ionizing radiation (Gamma rays, X-rays) and non-ionizing radiation (UV-A) can sometimes be used as sterilants. Although heat is the reliable means of sterilization, heat-sensitive material chemicals, either in a gaseous or liquid form, can be used. Ethylene oxide, nitrogen dioxide, ozone, and hydrogen peroxide gas plasma are common among gaseous sterilants. In contrast, glutaraldehyde, formaldehyde, hydrogen peroxide, peracetic acid, chlorine, and phenolic compounds are frequently used as liquid sterilants. Heat-, irradiation-, or chemical-sensitive fluids (pharmaceuticals, proteins, and other biologics) are sterilized using membrane filters. In this process, nanofilters with a smaller pore size (ie, 20-50 nm) are used for virus removal. Aseptic processing technique like sealed packaging until use is required to maintain the sterility of the sterilized products. [Md. Rakibul Islam]