Exploring silk fibroin aerogels via different coagulation approaches

Aerogels are highly porous nanostructured materials with a high specific surface area, a very low density and a low thermal conductivity. Bio-aerogels, prepared from biopolymers, have gained interest for biomedical applications. While most bio-aerogels are polysaccharide-based, protein-based aerogels using silk fibroin (SF) from Bombyx mori cocoons remain underexplored. Our study delved into the impact of coagulation methods on SF aerogel properties, specifically, comparing ethanol treatment (Method 1) and sodium dihydrogen phosphate (NaH2PO4) (Method 2). Aerogels obtained through Method 1 exhibited a volume shrinkage of approximately 12-22 % and a density of about 0.06-0.07 g cm-3, while those obtained via Method 2 demonstrated a more substantial volume shrinkage of approximately 60-70 % and a higher density of around 0.2 g cm-3. These differences significantly influenced the internal structure of the aerogels, manifesting distinct morphological features of the materials. Mechanical tests revealed that SF aerogels derived from Method 2 displayed superior stress resistance at 80 % strain and higher elastic recovery when compared to samples of Method 1. In conclusion, the choice in coagulation methods broadens the mechanical property and density window for this type of aerogel which offers opportunities for a wide range of biomedical applications.