Yingtai: Application of Vacuum Freeze-Drying Technology in Medium Lyophilization

Yingtai: Application of Vacuum Freeze-Drying Technology in Medium Lyophilization

Cell culture technology has an immeasurable impact on human society. Recent advances in biology have largely depended on cell culture technology. Additionally, practical techniques based on cell culture have been developed across various fields, including new drug efficacy and toxicity assessments, vaccine and biopharmaceutical manufacturing, and assisted reproductive technologies. With somatic cell reprogramming recently becoming technically feasible, researchers worldwide are fiercely competing for leadership in regenerative medicine development. Similarly, in this field, cell culture technology is also considered fundamental for further development and widespread adoption.

1.The Importance of Culture Media

One of the most crucial factors in cell culture technology is the culture medium, such as Minimal Essential Medium (MEM), Dulbecco's Modified Eagle Medium (DMEM), DMEM-F12, and RPMI medium. These media not only have a profound impact on cell metabolism, redox state, and certain signal transduction pathways but also greatly affect cell morphology and differentiation. The medium maintains cell survival and proliferation, as well as cell function, meaning that the quality of the medium directly influences research outcomes, biopharmaceutical productivity, and the results of assisted reproductive technologies. Therefore, it is vital for researchers involved in cell culture to choose an appropriate medium that fits their goals. In some cases, researchers may need to adjust the medium's components themselves. Furthermore, when issues arise, researchers must understand the medium's characteristics to identify the causes of experimental problems.

In developing these media, the main goal is to ensure high cell proliferation rates and biomass growth at low cost, while avoiding frequent supplementation of nutrients. Currently, synthetic media can be categorized based on the type of supplements added, such as serum-containing media, serum-free media, protein-free media, and media with defined chemical components. Serum-containing media include various serum-derived substances, making the medium's composition unclear and its concentration variable between batches. This situation reduces the reproducibility of cultivation results and poses a risk of microbial contamination. However, serum-containing media are easily prepared and effectively used for various cell types, as serum contains numerous active substances essential for animal cell survival and growth. In contrast, serum-free media have defined components, achieving high reproducibility of results and allowing for validated cultivation processes. Moreover, if cultivation conditions are optimized for target cells, target cells can be selectively grown within mixed cell populations. Protein-free media (containing no proteins at all) and media with defined chemical components (excluding any undefined components) provide additional stability and reproducibility to the cultivation system, helping to identify cell secretions and reduce microbial contamination risks. However, designing serum-free media is challenging: to date, only specific cell types have been cultivated this way.

Currently, commonly used cell culture medium formulations are available on the market. Therefore, some researchers may generally be unaware of the detailed information and background of the media they use, especially regarding the fundamental principles of their development, exact components, and the types of cells for which these media are suitable.

2.Application of Lyophilized Medium Powder

Lyophilized medium powder is used in the preparation of products for skin repair, anti-skin aging, repair of oxidative stress damage to the skin, and repair of skin damage from ultraviolet radiation. Products include pharmaceuticals, skincare products, or cosmetics. By adding lyoprotectants, culture media containing a large amount of cell-secreted substances are freeze-dried into solid powders, stabilizing the properties of cytokines to maximize their efficacy. Specifically, the addition of trehalose, which acts as a lyoprotectant, preserves the activity of cytokines in the conditioned medium and also has antioxidant properties that delay cell aging.

Traditionally, the culture medium used for peripheral blood lymphocyte chromosome preparation is typically based on a liquid medium (such as RPMI1640) supplemented with a certain amount of serum and plant hemagglutinin (PHA). The use of PHA stimulates lymphocytes in the G1 phase to enter the mitotic cycle, allowing for chromosomal karyotype analysis. However, liquid lymphocyte culture media are unsuitable for storage at room temperature, as active substances such as glutamine and PHA are prone to inactivation. Even after storage at 2-8°C for some time, the number of lymphocytes in the mitotic phase suitable for karyotype analysis significantly decreases. Freeze-drying technology to prepare lyophilized medium powder is a solution to these issues. However, to date, there have been few public reports providing specific lyophilization processes or methods for media.