Lyophilization

1. Why are the proteins lyophilized? How will lyophilization affect the characteristics of the proteins?

Lyophilization (freeze-drying) technique is applied to increase the stability and shelf life of proteins, and decrease shipping cost.

Lyophilization may cause loss of activity or aggregation of proteins. But addition of protectants (stabilizers, additives, excipients) and proper control of lyophilization conditions will minimize the adverse effect for most proteins.

2. Why are protectants added to protein solutions before lyophilization? What protectants do you add to your products?

Protectants (stabilizers) are added to protect proteins during lyophilization and/or long-term storage. Proteins are subjected to various stresses generated by lyophilization which may cause loss of activity, aggregation, or denaturation. Protectants can alleviate the stresses by several mechanisms including formation of an amorphous glassy state, replacing water, hydrogen bonding to proteins, physical dilution and separation of protein molecules, etc. Common protectants/stabilizers include sugars, polyols, polymers, surfactants, as well as some proteins and amino acids. We use trehalose and mannitol (normally 8% w/v) as protectants for lyophilization.

Trehalose is a non-reducing disaccharide, well-known for its ability to stabilize biomolecules and microorganisms during prolonged period of desiccation.

Mannitol is also commonly used as a stabilizer as well as a bulking agent in the process of lyophilization. It was reported to reduce aggregation for some proteins during lyophilization.

3. How to reconstitute the lyophilized powder? Should I use sterile water, PBS or other buffer?

We recommend using sterile water for reconstitution. Add the recommended volume of sterile water of to the vial, and gently shake it to solubilize the protein completely. Do not shake violently. PBS or other buffer can also be used as reconstitution agent as the salts in PBS can be omitted when the concentration and reconstitution volume is low. If possible, we suggest you compare the results of different reconstitution agents.