Flexible, Water-Absorbing Silk Fibroin Biomaterial Sponges with Unique Pore Structure for Tissue Engineering

Silk fibroin (SF) scaffolds are widely used in tissue engineering due to their biocompatibility and slow biodegradability. However, the relatively stiff mechanical properties and low permeability of these systems can limit some applications. In this study, a new type of water-stable silk sponge (ASF-PEG-S) was obtained by inducing nanoparticle (50-300 nm diam.) formation in SF solution by autoclaving, followed by freeze-drying and rinsing the dry sponges with low molecular weight (400 Da) polyethylene glycol (PEG400) to induce SF β-sheet structure formation and thus stability in water. With further extraction, the SF nanoparticles embedded in the sponges were removed, leaving nano-pores in the walls of round-shaped micro-size pores. The unique pore structure resulted in enhanced permeability and flexibility of these ASF-PEG-S when compared to other types of SF sponges, especially with respect to commonly used methanol-annealed SF sponges. In addition, ASF-PEG-S absorbed water nearly 40 times more than the...