Effect of β‐Sheet Crystals on the Thermal and Rheological Behavior of Protein‐Based Hydrogels Derived from Gelatin and Silk Fibroin

Abstract Summary: Novel protein‐based hydrogels have been prepared by blending gelatin (G) with amorphous Bombyx mori silk fibroin (SF) and subsequently promoting the formation of β ‐sheet crystals in SF upon exposure to methanol or methanol/water solutions. Differential scanning calorimetry of the resultant hydrogels confirms the presence and thermoreversibility of the G helix‐coil transition between ambient and body temperature at high G concentrations. At low G concentrations, this transition is shifted to higher temperatures and becomes progressively less pronounced. Complementary dynamic rheological measurements reveal solid‐liquid cross‐over at the G helix‐coil transition temperature typically between 30 and 36 °C in blends prior to the formation of β ‐sheet crystals. Introducing the β ‐sheet conformation in SF stabilizes the hydrogel network and extends the solid‐like behavior of the hydrogels to elevated temperatures beyond body temperature with as little as 10 wt.‐% SF. The temperature‐dependent elastic modulus across the G helix‐coil transition is reversible, indicating that the conformational change in G can be used in stabilized G/SF hydrogels to induce thermally triggered encapsulant release. Thermally reversible helix‐coil conformational transition of gelatin in mixed gelatin/silk fibroin hydrogels. magnified image Thermally reversible helix‐coil conformational transition of gelatin in mixed gelatin/silk fibroin hydrogels.