The Principles of Medical Device Decontamination

The enzymes are designed to break down larger molecules into smaller, more water- soluble ones, a process known as hydrolysis, and are extremely efficient biocatalysts, which are proteins that accelerate chemical reactions supporting the degradation of specific bonds. These enzymes are very selective and only target specific soil components and will have negligible effects on other molecules. The detergent formulation is typically neutral to mild alkaline pH in order to prevent damage to these enzyme proteins. These enzymatic detergents generally work better in immersion systems used for manual cleaning but are also widely used in automated washer-disinfectors. Enzymes are typically named after the substances they help to break down; for example, proteases help to break down protein, amylases help to break down starch, lipases help to break down fats/lipids and cellulases help to break down cellulose; typically, however, only proteases are useful in medical device cleaning formulations due to protein being of particular interest as a model soil. Different proteases can be combined to broaden pH or temperature effectiveness, but using a higher concentration of the same enzyme will not necessarily increase efficacy; enzymes are only one part of the process of breaking down soils, and other elements are still required to wash and remove all types of soil. An important note is that enzymatic detergents that contain multiple enzymes, i.e. protease, amylase and lipase may be unstable in the presence of one another. Studies have shown relatively rapid destruction of one enzyme by another enzyme in as little as a few months’ storage at room temperature; this degradation may be much faster at elevated temperatures. Alkaline detergents are detergents that contain alkalis as well as surfactants. These alkaline detergents are so-called as they form a solution in water that is high in pH, typically greater than pH 10; they usually contain metal hydroxides such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), producing the hydroxide ion (OH-) in aqueous solutions. These detergents demonstrate high efficacy at removing fats, oils and proteins, as the alkali results in hydrolysis of large proteins and lipids, breaking them into smaller water-soluble pieces. They are more effective at higher temperatures (greater than 60˚C), but high pH and high temperature may have material compatibility issues (i.e. alkaline corrosion), however this is very much dependent upon the concentration used.

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