Moisture content in proteins: its effects and measurement

Area of Science:

• Pharmaceutical Science
• Solid-State Chemistry
• Biophysics

Background:

• Residual moisture content critically influences the solid-state stability of biopharmaceutical products.
• Protein degradation is minimal at low hydration levels (monolayer) but accelerates beyond this due to increased protein flexibility and water mobility.

Purpose of the Study:

• To investigate the impact of residual moisture on protein stability in lyophilized formulations.
• To highlight the importance of accurate moisture determination for resolving stability issues.

Main Methods:

• Review of techniques for moisture determination in solid-state biopharmaceuticals.
• Analysis of water's role as a plasticizer affecting the glass transition temperature (Tg).
• Consideration of excipient effects on water-protein interactions.

Main Results:

• Moisture content beyond the monolayer significantly increases protein degradation rates.
• Temperature and lyophilized plug composition are key variables affecting amorphous solid-state protein stability.
• Excipients can alter water availability to proteins through ion effects or crystallization.

Conclusions:

• Accurate and precise moisture determination is essential for understanding and mitigating protein degradation in solid-state formulations.
• Controlling residual moisture is vital for ensuring the long-term stability and efficacy of biopharmaceuticals.