For years alkaline detergents have been used in the cleaning of organic soils from multiple surfaces and substances. They are used in the food industry for flatware, dishes and pots and pans, for the cleaning of laundry both in the home and large scale commercial laundries, in labs for the cleaning of glassware, in life sciences, for cage cleaning and are a favorite in Europe for surgical instrument cleaning.
Alkaline detergents can vary in pH from mildly alkaline (pH 9.5-10) to highly alkaline (pH12-13). Alkaline detergents work by chemically changing organic soil. Alkali’s hydrolyzing peptide bonds, breaking down large insoluble proteins into smaller more easily soluble polypetides. Alkali also works on fats by the process of saponification, which changes fats into soap and glycerin. Alkaline detergents are best suited for mechanical washers because these washers lack the friction that manual cleaning provides through brushing or the cavitation provided from ultrasonic cleaners. Alkaline detergents are usually less expensive than enzymatic detergents but require a higher wash temperature of around 175°F to work properly.
So why are we in the US so hesitant to use alkaline detergents to clean surgical instruments? First off is that they are corrosive if not dosed properly. Highly alkaline detergents are caustic and not suitable for all materials, a detergent with the pH of 12 should never be used on anodized aluminum (e.g. rigid containers) because it will begin to break down the anodized coating of the aluminum well within 10 washes. Also unless formulated with the right buffers (e.g. deconex Alka One-x http://www.potomaclabs.com/deconex-28.php ), high alkaline detergents need to be followed with a correctly dosed acid rinse to neutralize any residuals left on the instruments. If they are not buffered or neutralized properly they will begin to remove the passivation layer from stainless steel and corrode the instruments.
On the other hand we have “neutral” pH detergents and “neutral” pH enzymatic detergents. Both forms of neutral pH detergents have a pH range from 7-8.5. Plain Neutral pH detergents are usually considered to be “gentle detergents”. Those intended for use with surgical instruments will normally contain surfactants, chelating agents and if properly formulated anti-corrosive agents. They contain nothing that chemically changes organic soil, but instead depend on their surfactants to lift and remove organic soil from surfaces. There are a few neutral pH detergents that are formulated not only to clean organic soil, but are also capable of removing the residues of High Level Disinfectant from scopes before switching disinfecting processes from aldehydes to amines or visa-versa (e.g. deconex 36 Intensive-x http://www.potomaclabs.com/deconex-36.php ).
Neutral pH enzymatic detergents “pack the kick” for chemically changing organic soil by the addition of the enzymes. Enzymes are Bio-Catalytic protein’s, they break large organic molecules into their smaller building blocks. Unlike alkaline’s which target multiple organic substances at once enzymes are specific to the soil they are breaking down. Protease enzymes break down protein, lipase enzymes break down fats, amylase breaks down carbohydrates. The enzymes in neutral pH enzymatic detergents are produce by bacteria. Subtilisin a protease enzyme was originally obtained from the growing of the bacteria Bacillus subtilis. Presently numerous bacteria and fungi can be engineered to produce specific enzymes, so enzyme manufacturers are not dependent on just one type of bacteria ( e.g Bacillus subtilis) to produce the enzymes they need. Neutral pH enzymatic detergents require a temperature of between 90°F-140°F to do their work. Low temperatures will make the enzymes sluggish and they will not catalyze their target soil properly and temperatures above their working range will denature them. Also until recently most enzymatic detergents were not as efficacious at removing fibrin from surgical instruments as alkaline detergents. The discovery that cellulase will break down this insoluble protein in dried blood has changed this paradigm. Now multi-enzymatic detergents that contain cellulase (e.g. deconex Power Zyme http://www.potomaclabs.com/power-zyme.php ) do a comparable job to the cleaning power of alkaline detergents when it comes to fibrin removal.
Lastly it should be mentioned that a combination of multi-enzymatic and mildly alkaline (pH9-10) detergents has shown to harness the ability of both modes of cleaning into a superior cleaning system especially suited for difficult to clean instruments like daVinci endowrist® instruments (e.g. deconex Twin pH10/ Twin Zyme http://www.potomaclabs.com/deconex-twin.php ) These are normally packed in separate containers and dosed into the washer disinfector during the wash phase of cleaning. In the validation study of the deconex Twin System and the Belimed daVinci load carrier for endowrist instruments not one of the instruments in the study had a proteinaceous soil level “above the alert value of 100μg. In fact if you have a dishwasher at home and use pod packed detergent with separate compartments you are already using a similar system on your dishes. The reason for the separate container/compartments is because if you were to combine the chemistries in one container or “pod” they would “cannibalize” each other, but when combined in “concert” in the washer they support each other to gently remove the toughest of organic soils. The separate packaging of these chemistries has recently been overcome by the scientific staff at Borer Chemie. Their latest product deconex Prozyme Alka http://www.potomaclabs.com/deconex-prozyme-alka.php is a multi-enzymatic mildly alkaline detergent all in one container. It has no know material compatibility and is even mild enough for use on anodized aluminum, yet its superior clean power is capable of breaking down the toughest of organic soils like fibrin and biofilms. Like all Borer Chemie products it is extremely environmentally friendly to the point that it contains no EDTA or NTA. These chelating agents are widely used in detergents to “soften water” but pose major environmental threats because they accumulate and remain in water unchanged for long periods of time.