Precautions for the use of cell culture medium powder

I. Storage Conditions

1. Moisture – proof
   • Cell culture medium powder is highly hygroscopic. Once it gets damp, the powder may clump, which will not only affect its solubility but also lead to uneven distribution of nutrients. For example, some crucial amino acids and vitamins may have locally too high or too low concentrations during the clumping process, thus affecting the results of subsequent cell culture. Therefore, it should be stored in a dry environment, and desiccants (such as silica gel) can usually be used to keep the inside of the storage container dry.
2. Avoid High Temperatures
   • High temperatures can cause some components in the culture medium powder to denature or decompose. For example, some growth factors will lose their activity at high temperatures, and some temperature – sensitive vitamins will also be destroyed. Generally, cell culture medium powder should be stored at room temperature (15 – 25 °C), avoid direct sunlight, and must not be placed near heat sources (such as heaters, ovens, etc.).
3. Prevent Oxidation
   • Some components (such as certain trace elements and antioxidants) in some culture medium powders are prone to oxidation. Oxidation may change the chemical properties of these components, thereby affecting the overall performance of the culture medium. It is recommended to use well – sealed containers for storage, and use up the powder as soon as possible after opening the container. If it cannot be used up at one time, the container should be strictly sealed.

II. Preparation Process

1. Accurate Weighing
   • When preparing the culture medium, it is crucial to accurately weigh the cell culture medium powder. If the weighing is inaccurate, the proportion of various nutrients in the culture medium will be unbalanced. For example, if the amount of amino acids is too much or too little, it may affect the protein synthesis of cells; inaccurate content of inorganic salts may disrupt the osmotic pressure balance of cells. Therefore, a balance with high precision should be used for weighing and operations should be carried out according to the requirements of the product manual.
2. Dissolution Operation
   • When dissolving the powder, the powder should be slowly added to an appropriate amount of ultrapure water while stirring. The stirring speed should not be too fast to avoid generating too many bubbles. Bubbles may carry air into the solution, resulting in an excessively high dissolved oxygen content in the solution, which is unfavorable for the culture of some anaerobic cells. In addition, if the powder is not completely dissolved, the remaining undissolved particles may affect the growth environment of cells.
3. Order of Addition
   • When other components (such as serum, antibiotics, growth factors, etc.) need to be added to the dissolved culture medium, attention should be paid to the order of addition. Generally, serum is added first because serum can provide some basic nutrition and protection for cells. Then antibiotics are added to prevent bacterial contamination. Finally, more sensitive components such as growth factors are added, because these components may react with other substances and lose their activity. For example, if some growth factors are added before serum, they may be decomposed by some proteases in the serum.

III. Quality Control

1. Check the Expiration Date
   • Cell culture medium powder has a certain expiration date. After the expiration date, the nutrients in the powder may degrade or deteriorate. Before use, be sure to check the production date and expiration date of the powder to ensure the use of products within the expiration date. Even within the expiration date, if there are abnormal changes in the appearance, color, or smell of the powder, it should be used with caution or discarded.
2. Aseptic Operation
   • During the entire preparation process, ensure that the operating environment is sterile. Because the culture medium provides nutrients for cell growth, if it is contaminated by microorganisms during the preparation process, these microorganisms will multiply in large numbers in the culture medium, compete with cells for nutrients, and produce toxins, ultimately leading to the failure of cell culture. The preparation should be carried out in a sterile environment such as a laminar flow cabinet, and the containers and tools used should be strictly sterilized.
3. pH Adjustment
   • The prepared culture medium needs to have its pH adjusted to a range suitable for cell growth. Different cell types have different pH requirements, but most cells grow well in an environment with a pH of 7.2 – 7.4. When adjusting the pH, an accurate pH meter should be used for measurement, and appropriate acid – base solutions (such as hydrochloric acid and sodium hydroxide) should be used for slow adjustment to avoid large fluctuations in pH that have adverse effects on cells.