Pipette tubes are regarded as one of the most essential utensils in the laboratory, and they enable the measurement of the amount of liquid and the transfer of it from one vessel to another. Since these tubes are utilized often to manipulate many different chemicals and biological specimens, they must not be contaminated. Sterilizing pipette tubes is one of the most elementary methods in laboratory practice, but even slight contamination is critical in microbiology, molecular biology, and chemistry. This article contains information on the methods of sterilization of pipette tubes, the recommendations, problems, and the importance of the sterile environment in the laboratory.
Sterilization of the pipette tube is crucial to avoid any complications that may arise in laboratory experiments. The presence of bacteria, viruses, fungi, or chemical residues may introduce variables that may lead to inaccurate results. Non-sterile pipette tubes are very dangerous to use in clinical and diagnostic situations because they increase the possibility of cross-contamination, which may lead to the wrong diagnosis or treatment regimen. Therefore, proper sterilization methods should be employed for scientific purposes, safety, and reliability in clinical practice.
The common methods are autoclaving, dry heat sterilization, chemical sterilization, and UV sterilization. All the methods are good and bad in their way, and the choice of the process depends on the kind of experiments that will be carried out.
The name ‘STERIS’ has become the gold standard in sterilization.
Sterilization of pipette tubes is widely believed to be best done through autoclaving. This process involves using high-pressure saturated steam between 121°C and 134°C. Hot and pressure eliminate all types of microorganisms, including bacterial spores, which are very difficult to destroy by other sterilization methods.
To autoclave pipette tubes, they are usually placed in autoclave racks or trays that allow steam to penetrate each pipe. This is also true when filling the tubes so they do not touch one another, as this may affect the steam distribution and, thus, inadequate sterilization. The autoclave cycle for pipette tubes normally takes 15-20 minutes, and another cycle is needed to ensure no moisture on the tubes.
Dry heat sterilization involves putting pipette tubes in an oven and heating them at 1600C and 1800C for 1-2 hours. It differs from autoclaving in that it does not employ moisture, making it suitable for sterilizing glass pipette tubes and metal parts that may rust or be betrayed by steam.
Dry heat sterilization of pipette tube is done in a sterilization oven, and the tubes should not touch or be in close contact. This arrangement allows hot air to cover each tube evenly so that all the surface areas attain the required temperature. When the sterilization process is complete, the tubes are left in the oven to cool to prevent thermal shock that may cause the glass tubes to crack.
Dry heat sterilization is most useful for eliminating microbial load and bacterial spores, mainly through the oxidation of cell constituents. However, it is slower than autoclaving and uses more energy. Heat sterilization should not be used on plastic pipette tubes because the heat weakens the plastic and can make it melt or warp.
Chemical sterilization involves using a liquid or gaseous chemical to sterilize pipette tubes. It applies to tubes that cannot be sterilized through heat, such as plastics or rubber. Chemical sterilants include ethylene oxide, hydrogen peroxide, glutaraldehyde, and peracetic acid. Such chemicals can inactivate microorganisms by disrupting their cell walls and other functions.
Before chemical sterilization, pipette tubes are rinsed to eliminate any organic matter that may react with the sterilizing agent. Depending on the kind of chemical to be employed and the pollution level, they are placed in or covered with the chemical agent for a given time. After the exposure, the tubes are washed with sterile water to remove any remnant of the chemical that may interfere with other experiments to be carried out.
Chemical sterilization benefits materials that cannot be subjected to autoclave or dry heat sterilization. However, this process takes longer and should be well handled and aired since most chemical sterilants are hazardous to human health. In addition, some chemicals may leave deposits that are difficult to remove, affecting the pipette tubes' efficiency.
UV sterilization is a non-thermal sterilization process in which short-wavelength UV light, particularly UV-C light, is used to disinfect pipette tubes by inactivating microorganisms on the surface of the tubes. UV radiation destroys microorganisms by affecting their DNA and RNA, thus preventing their reproduction and killing the cells.
UV sterilization is most suitable for sterilizing the outer surface of pipette tubes, which is very helpful for those already autoclaved pipettes that can be reused after some time or for those pipettes that are to be autoclaved again for some other experiment. However, UV light could be more penetrative. It is less effective in removing the interior surface of pipette tubes or any other part that is not directly exposed to the light.
For UV sterilization of pipette tubes, the tubes are arranged in a UV sterilization cabinet or under a UV lamp so that all the surfaces of the tubes are exposed to light. The exposure time can vary from several minutes to one hour, depending upon the intensity of UV light and the extent of contamination. The main advantage of UV sterilization is that the materials are sterilized without heat or chemicals, and therefore, the properties of the materials are not altered.
Some key considerations include:
Proper Cleaning Before Sterilization: Another precaution is to ensure that pipette tubes are well cleaned before the sterilization process so that no organic material is left behind, as this will affect the sterilization of microorganisms. Cleaning also helps to prevent the buildup of residue that may reduce the effectiveness of the pipette tubes.
Choosing the Right Sterilization Method: It is advisable to select the most appropriate sterilization method according to the material used in the pipette tubes and the anticipated contaminants. Most applications prefer autoclaving, while other methods, like dry heat, chemical treatment, or UV exposure, are suitable for heat-sensitive materials.
Validation and Quality Control: It is also important to periodically examine the efficiency of the sterilization process. This can be done by biological tests, chemical tests, or using spore strips to check that the sterilization parameters have been achieved.
Proper Handling and Storage: If pipette tubes have been sterilized, they should not be touched roughly to avoid contamination. They should be stored clean, preferably in a sterile container or bag.
Pipette tube sterilization is one of the most crucial procedures that should be observed in the laboratory to avoid invalidating experiments. By understanding the various sterilization methods and practicing the right measures, laboratory personnel can sterilize pipette tubes, reducing contamination and providing accurate experiment results. This paper has demonstrated that no matter the method used, whether autoclaving, dry heat, chemical sterilization, or UV irradiation, the principles of pipette tube sterilization are preparation, validation, and handling.
The most prevalent technique is autoclaving. It involves applying pressure steam at 121°C for 15-20 minutes. The autoclave process is efficient in eliminating microorganisms, including resistant bacterial spores.
Yes, pipette tubes can be sterilized with dry heat if they are heat resistant. Usually, this requires a heat treatment at 160°C to 180°C (320°F to 356°F) for 1 to 2 hours.
Another sterilization method is using chemicals, especially when the pipette tubes are heat-sensitive. Chemical reagents such as ethylene oxide or hydrogen peroxide vapor are used to clean the tubes.
