Protein Preservation in Sugar Glasses
Jerainne Johnson, Marcus Cicerone
Polymers Division, National Institute of Standards and Technology
Gaithersburg, MD 20899-8543
The storage of bio-agents in their dry form is of keen interest globally especially as it relates to stock piles for applications in biological defense, drug delivery and vaccines. Storage at ambient or elevated temperatures is sometimes required and thus the need for a suitable medium is desired.
Glasses are the most likely candidate for such a medium for protein storage at ambient temperatures and above. In particular, sugar based glasses are thought to stabilize proteins through slowing down their dynamical processes, which for example suppresses motion based structural degradation.
Structural (α) relaxation is often used to relate host dynamics with degradation timescales for biological materials embedded in glasses. Recent formulation studies however, have failed to establish a correlation between increased glass transition temperatures, Tg (a measure of a relaxation) and protein stability. These results are potential indication of additional dynamics that also play an important role in the biostabilization in glasses.
Results from neutron scattering experiments show distinct correlation between stability of model proteins in glasses and the fast (ps – ns), local (sub-Ångstrom) dynamics of the glass itself. These observations have been confirmed by more recent studies with therapeutic proteins, which show correlations between fast dynamics and protein degradation rates. Investigating these fast dynamics within the glass and the protein system will allow us to optimize the glass medium against specific degradation pathways.