First of all, we need to know why more and more companies tend to freeze-dry various proteins, because the stability of proteins in dry powder state is higher, and it is easier to transport and store than liquid reagents, so protein freeze-drying has become a a big trend.
The most commonly used method for changing from liquid reagents to dry powders is low-temperature vacuum drying to remove moisture to form dry powders. In this low-temperature environment, the protein structure is easy to change, which may affect the function of the protein, so freeze-drying is necessary. For those with protective agents, the functions of different types of protective agents will be different.
Summarize what are the commonly used freeze-drying protective agents? Mainly divided into five categories:
1. PH buffer, protein stability is greatly affected by ph, when choosing a buffer with a high ph, try not to approach the isoelectric point of the protein to avoid protein aggregation, tris, histidine, and citrate are frozen During the drying process, there will be a small pH change, and the pH of the buffr solution generally selected is 5.8-8.0.
2. Filling agent, in order to ensure that the freeze-dried product forms a good structure to prevent the product from collapsing, and also to increase the solubility of the formula, the filling agent must be fully soluble and compatible with the protein. The commonly used filling agent is manna alcohol, glycine, bovine serum albumin, etc.
3. Sugars, sugars are excipients in the process of protein freeze-drying, because sugars contain more hydroxyl groups, which can replace the hydrogen bonds between proteins and water to provide stability, generally disaccharides, such as Sucrose and Trehalose.
Fourth, non-ionic surfactants can reduce protein aggregation, the most commonly used is Tween 80.
5. Ligands, sometimes some ligands are added to improve the thermodynamic stability of the protein.