Optimizing Molecular Weight of Lyophilized Silk As a Shelf-Stable Source Material

Area of Science:

• Biomaterials Science
• Protein Chemistry
• Materials Engineering

Background:

• Liquid storage of silk proteins leads to premature gelation and waste.
• Existing methods for stabilizing silk solutions are insufficient for long-term storage.
• A need exists for shelf-stable silk protein formats for on-demand applications.

Purpose of the Study:

• To develop a lyophilization strategy for creating stable, soluble silk fibroin powders.
• To investigate the impact of molecular weight on the stability and solubility of lyophilized silk.
• To demonstrate the utility of stored silk powders for generating various material formats.

Main Methods:

• Silk fibroin solutions of varying molecular weights were lyophilized.
• Stability and solubility of lyophilized silk powders were assessed after storage.
• Characterization techniques included circular dichroism and dynamic light scattering.
• Silk materials (films, gels, scaffolds) were fabricated from reconstituted powders.

Main Results:

• Shelf-stable lyophilized silk fibroin powders (moderate to low molecular weight) were successfully developed.
• These powders remained fully soluble and structurally intact after one year of storage, even at elevated temperatures.
• Higher molecular weight silk powders exhibited reduced solubility due to aggregation and increased β-sheet content.
• The lyophilization protocol, including secondary drying, did not negatively impact long-term powder stability.

Conclusions:

• Lyophilization offers a flexible and cost-effective method for producing shelf-stable silk fibroin stock materials.
• Moderate to low molecular weight silk fibroin powders are ideal for long-term storage and on-demand use.
• This approach facilitates the stockpiling of silk materials for diverse applications, including in field settings.