Effect of Gelation Route on Pore Architecture, Swelling, and Degradation of Silk Fibroin Lyogels

Silk fibroin (SF) lyogels are promising biomaterials for tissue engineering and drug delivery, but their performance depends strongly on pore architecture and degradation behavior. In this study, we compared lyogels prepared from naturally self-agglomerated SF and ultrasonicated SF to determine how gelation route influences pore morphology and related physical properties such as swelling and degradation. Regenerated aqueous SF was prepared from Bombyx mori silk, gelled either by storage-induced self-agglomeration (5% w/v) or ultrasonication (7% w/v), and then freeze-dried to obtain porous lyogels. The materials were evaluated for swelling kinetics, pore morphology, hydrophilicity, in vitro degradation and release kinetics. Self-agglomerated lyogels exhibited smaller and more uniform pores, slower swelling, and prolonged structural integrity, whereas ultrasonicated lyogels showed larger, less homogeneous pores and rapid water uptake. Ultrasonicated lyogels absorbed up to ~1800% of their dry weight within 1 h, while self-agglomerated lyogels absorbed <1000% but continued swelling for more than one week. Under enzymatic degradation with Protease XIV (1 U/mL), ultrasonicated lyogels degraded completely within 48–72 h, while self-agglomerated lyogels retained their shape beyond 4 days. Additionally ultrasonicated sponges showed faster release (T₅₀% ≈ 0.68 ± 0.01 hr), i.e., 41 mins, whereas self-agglomerated sponges exhibited slower release (T₅₀% ≈ 1.03 ± 0.04 hr), i.e., 64 mins. These findings show that controlling SF gelation is an effective strategy to tune pore size, swelling, and degradation, enabling rational selection of lyogels for burst-release versus sustained-release systems and for tissue engineering applications.