| Buffering agents |
Keeping the pH of protein solutions |
Usually, the buffers work in the range of 3–10 for proteins. In certain conditions, some buffers may be decomposed, and their by-products destroy the protein structure. |
| Chelators and antioxidants |
The roles of antioxidants and chelators are to prevent and/or remove oxidazing factors. |
Some reducing agents such as glutathione and ascorbic acid in the presence of metals and enhancing oxidation stresses can have a negative/destructive role on protein structure, although these agents are used in the pharmaceutical sector of proteins. |
| Proteins |
By interacting with therapeutic peptides, excipient proteins can increase the blood circulation time. |
Nowadays, chaperones have been given a special look as a preservative for medicinal proteins. |
| Polymers |
Maintaining the structure of proteins |
The main examples of this group include polyvinyl alcohol, dextran and hydroxyethyl starch. |
| Amino acids |
Buffering properties, preferential interactions, favored hydration, antioxidant effect and strong binding to protein regions |
Glycine (buffering agent and bulking agent during lyophilization), arginine (solubilizing agent and works as chaperone) and histidine (antioxidant and buffering agent) |
| Sugars and carbohydrates |
Forming a crystal network with preferential interactions |
Sorbitol in lyophilization and liquid formulation conditions, has a stabilizing role, however, in freezing conditions, due to the formation of sorbitol crystals, it assumes a stabilizing role. |
| Salts |
Tonicifying agent, reacting with the charged surfaces of proteins and take two stabilizing or destabilizing paths. |
Among the cations and anions of the Hofmeister series, the latter has dual protective/destructive effects on proteins. |
| Antimicrobial preservatives |
Preventing the growth of bacteria in solution-rich medicinal proteins |
m-cresol, phenol and benzyl alcohol are among the popular.
|
| Surfactants |
Reducing the interface area of solution and air during purification (inner wall of purification column and dialysis bags, etc.).
|
In this group, polysorbate 20 (PS20) and polysorbate 80 (PS80) are the most used in protein drugs and especially antibodies. |
| Osmolytes |
Generating favored hydration, preferential interactions, and polar interactions |
Sorbitol, sucrose, glycine, and trehalose have been able to reach the pharmaceutical sector |
