Embryo development takes place in a special culture media. Like the internal environment of the body, culture media should not only be optimally balanced in terms of trophic factors and essential amino acids composition, but also contain the necessary salts and a buffer system to stabilize osmolarity and pH. These two indicators are critical for embryo survival in vitro. When working in the laboratory, we prepare dishes for culture and manipulation, and at this moment it is extremely important to monitor the speed of this process.
The faster the embryologist copes with such a task, the less water will evaporate from the microdroplet of the medium, which means that its osmolarity will change less. To prevent the media evaporation, the droplets are covered with a layer of mineral oil, which provides additional protection for culture drops from external influences.
The second important indicator of the medium state is its pH. The pH value characterizes the concentration of hydrogen ions in the solution and is equal to inverse decimal logarithm of their concentration. Optimal pH for embryos is about 7.32 – 7.34. As you can see, this is a fairly narrow range of its changes. To stabilize the pH, buffer solutions are used.
Embryo culture is carried out in an incubator with a CO2 percentage close to its value inside the body – 5 – 6%. A bicarbonate buffer system is used to maintain the pH during the culture. During the work process, it is necessary to be sure that the pH value does not exceed the limits critical for normal function of the embryo cells throughout the entire time of culture.
Another important laboratory indicator is the temperature. The optimal temperature for work and culture is the normal human body temperature of 37 ° C. A temperature decrease can lead to depolymerization of microtubules and disruption of the cell cytoskeleton. Therefore, the temperature will be most critical for oocytes at the MII stage, when the chromosomes are lined up in a metaphase plate preparing to diverge to the cell poles. At this stage, fertilization takes place, which makes it necessary to carefully monitor any changes in temperature during the process.
An important parameter is the laboratory air purity. Although embryos spend most of their in vitro existence inside special incubators, there is a need for various manipulations when embryos are removed from this favorable environment. In addition, during the culture process, part of the ambient air gets inside the incubator, one way or another. Embryos are sensitive even to short-term minor environmental changes. It should be noted that this sensitivity manifests more the earlier stage the embryo is at. In the IVF laboratory, we are just facing the very beginning of the embryo life path, which will be critical for further normal individual development.
Currently, it is impossible to imagine an IVF center without modern equipment, including air purification and air conditioning systems. Our laboratory is equipped with a specially developed system of separate ventilation inside the clean zone, and is a completely sealed autonomous room. Separately, there is constant air filtration in those areas where we work with embryos outside the incubators. In special workstations, a constant airflow is created without turbulence. It completely blows away all particles from the work area and ensures the highest class of air purity in places for gametes and embryos handling.
Thanks to a variety of high-precision sensors and an alert system, all parameters important for the normal development of embryos can be evaluated not only directly during operation, but also at those moments when there is no one in the laboratory except the embryos themselves. This gives confidence that all the laboratory protocols are performed correctly, and in case of unforeseen situations, there is a possibility to fix it even before any impact on the cultured embryos.