Structure and properties of silk hydrogels

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Biophysics

Background:

• Silk fibroin is a natural protein with potential for biomaterial applications.
• Understanding its aqueous processing is crucial for both in vivo and in vitro applications.
• Environmental factors influence protein self-assembly and hydrogel formation.

Purpose of the Study:

• To investigate the effect of silk fibroin concentration on gelation and hydrogel properties.
• To assess the impact of environmental factors (temperature, ions, pH, PEO) on silk fibroin gelation.
• To correlate structural and morphological changes with mechanical functionality.

Main Methods:

• Controlled manipulation of silk fibroin concentration using osmotic stress.
• Systematic variation of environmental factors: temperature, Ca(2+), pH, PEO, and K(+).
• Characterization of gelation kinetics, structural transitions (FTIR), morphology (SEM), and mechanical properties (compressive strength, modulus).

Main Results:

• Gelation time is sensitive to protein concentration, pH, temperature, Ca(2+), and PEO, but not K(+).
• Silk fibroin transitions from a random coil to a beta-sheet structure upon gelation.
• Hydrogels (>4 wt % fibroin) exhibit network/spongelike structures; pore size is influenced by fibroin concentration, gelation temperature, and Ca(2+) concentration.
• Mechanical strength and modulus increase with higher protein concentration and gelation temperature.

Conclusions:

• Osmotic stress and environmental factors provide effective control over silk fibroin hydrogel formation and properties.
• The findings offer insights into natural silk processing in glands and guide in vitro material development.
• Tailoring hydrogel characteristics is achievable by modulating protein concentration and processing conditions.