Hot air sterilization

Controlling contamination when incubating cell cultures


Eliminating human-pathogenic germs: Hygiene vs. bacteria


To prevent contamination by unwanted germs, suitable precautions must be taken based on the specific application. Medical and pharmaceutical applications in research and in the field distinguish between the processes of disinfection and sterilization. In many cases, disinfection alone is not sufficient where there is a need to effectively eliminate bacteria, viruses and fungal spores, since disinfecting only reduces the number of germs with the aim of protecting against infections.  

On the other hand, when products manufactured for medical or pharmaceutical use must remain free of human-pathogenic microorganisms, sterilizing all instruments and tools is preferable to disinfection. This is the only way to achieve the required process stability for complicated procedures such as cell cultivation in CO2 incubators, for example.  


Methods of sterilization

Sterilization utilizes both physical and chemical methods. Surfaces, tools and instruments can be sterilized by exposure to high temperatures from water vaporization (under pressure) or dry heat, UV radiation, gassing, or chemical treatment. Choosing the right sterilization method depends on the material properties of the items being sterilized (thermostability, geometric form) and the requirements specific to the application (e.g., no permissible residues), but it also depends on whether bacteria, viruses or fungal spores are to be eliminated. In addition, any potential resistance—an increasingly common phenomenon among bacteria in particular—should also be taken into account.



Dry heat sterilization at high temperatures: The highest possible level of safety 

Dry heat sterilization works with hot, dry air. It allows users to reliably kill human-pathogenic germs without leaving any residues. Complete decontamination is achieved through exposure to a specific temperature over a defined length of time, e.g., 180 degrees Celsius for 30 minutes. The advantage of this method is that decontamination is possible even for narrow openings or difficult-to-reach cavities in highly complex designs, which otherwise pose a risk as potential hiding spots for germs. 

The units used for this method—dry-heat ovens—run more cost-effectively than autoclaves that use water (steam sterilization), require less maintenance, and are extremely user-friendly. Their broad temperature range (e.g., from 5 to 300 degrees Celsius) means that, aside from dry heat sterilization, they can also be used for a number of other functions, e.g., for drying or heating samples.  

Dry heat sterilization is only suitable for materials which are not heat-sensitive, since unlike sterilization that uses steam, this method requires a higher temperature to effectively kill bacteria, viruses or fungal spores with dry heat. This means that reusable metal and glass instruments can be sterilized, for example. 


Special applications require specific measures

The sterilization methods currently available for laboratory instruments are already highly advanced. In some settings, however, steps must also be taken to effectively prevent the process environment from being contaminated. These cases include all procedures where the main focus is on cell cultivation, e.g., in cancer research, regenerative medicine, in vitro fertilization, diagnostic analysis, biosensor production, and many others. If cell cultures ultimately intended for external or internal use on humans are contaminated with germs, patients will be exposed to a very serious risk, one that can be life-threatening under some circumstances. Therefore, it is critical that all process steps be designed to be as safe as possible, with special emphasis on the process interfaces themselves. Even more important for us, as a manufacturer of simulation chambers, is the need to continuously enhance the safety precautions involved, and for you, the user, to put these measures into practice while also staying informed of the latest technological developments. 



Cell cultivation inside the CO2 incubator

Cell cultivation is performed in an environment that simulates the naturally occurring conditions of the material being incubated. In CO2 incubators, the supply of gas (carbon dioxide, oxygen, nitrogen) and temperature setting can be programmed accordingly and maintained with the help of sensors. What the in vitro cell cultures being grown don’t have, however, is their own defense system. The problem here is that unwanted microorganisms often feel equally at home in the same conditions that are ideal for the cell cultures. For example, bacteria from the Enterobacteriaceae family thrive at a temperature of 37 degrees Celsius. It is therefore essential to keep the germ load as small as possible by implementing effective hygiene precautions throughout all process steps. This means that, in addition to thoroughly disinfecting and sterilizing all surfaces, vessels and instruments used, choosing the right units, e.g. dry-heat ovens or CO2 incubators, also plays a major role. 


Two-in-one solution: Auto-sterilization for safety across all process steps

Our CO2 incubators place a special emphasis on high-temperature dry heat sterilization. The incubator interior must be sterile if cell cultivation is to be performed. To eliminate any possibility of contamination, we have integrated a program for auto-sterilization at 180 degrees Celsius (2 h) in our machines. To start the program, all the user needs to do is press a button after removing the sample. A special feature of our CB series incubators is that the CO2 sensor can be heat-sterilized and therefore does not need to be removed from the unit.  

The auto-sterilization program is based on the previous specifications of DIN 58947. Information on the test of the sterilization program that must be regularly conducted using biological indicators can be found in DIN EN ISO 11138-4 and DIN EN ISO 18472, which are available for purchase from the Beuth-Verlag publishing house. The publisher also offers regular training courses on various aspects of health care technology


BINDER units help ensure sterile work environment

The equipment and features of our cell-cultivation machines have been designed to create a sterile work environment using both dry heat sterilization and other additional measures. The units are extremely user-friendly, which eliminates errors and helps you to reliably produce safe products. One example of this is the seamless design of the inner chamber, which makes it easier to perform the required regular wipe-down disinfection. A special technology is used to keep condensation from forming, which also prevents accumulation of unwanted germs. The integration of a glass inner door gives users a view inside the chamber without letting in potentially contaminated outside air. And last, but not least: Our units include a highly sensitive automatic diagnostic system for continuous CO2 monitoring. 



When combined with our dry-heat ovens—which are available in a wide selection to meet various different requirements, and are a useful tool for sterilizing used lab instruments—these units help you reach the highest level of safety. 



You’re on the safe side with Binder CO2 incubators made in Germany

We offer two separate series in different sizes to incubate your cell cultures. Both series deliver the functionality to dry-heat sterilize the unit’s interior and come equipped with a seamless-design inner chamber, anti-condensation technology, and double doors. Our CO2 incubators also offer a number of other features, meaning that you’ll always find the right unit at Binder—for both routine procedures and highly sensitive applications.


Do you have further questions? Contact us!

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