Lyophilisation

Definition

Lyophilisation (freeze-drying) is the process of removing water from a peptide formulation by freezing it and then reducing the surrounding pressure to allow the frozen water to sublimate directly from solid ice to vapour. This produces a stable, dry powder that can be stored long-term without refrigeration in many cases.

Why Peptides Are Lyophilised

Peptides in aqueous solution are susceptible to hydrolysis, oxidation, aggregation, and microbial contamination, all of which degrade potency over time. Lyophilisation addresses these issues by removing the water matrix that enables degradation reactions. The resulting powder is typically stable for months to years when stored properly (cool, dry, protected from light).

The process involves three phases:

• Freezing — The peptide solution is frozen to create ice crystals
• Primary drying — Pressure is reduced and heat applied to sublimate ice
• Secondary drying — Residual moisture is removed at higher temperature under vacuum

Relevance to Peptide Research

Most research peptides are supplied in lyophilised form and require reconstitution with bacteriostatic water or sterile saline before use. Proper reconstitution technique is important — peptides should be gently swirled rather than shaken to avoid denaturation. The lyophilised cake or powder appearance can indicate quality: a uniform, fluffy white cake suggests proper freeze-drying, while collapsed or discoloured material may indicate process issues.