Porous structures from fibrous proteins for biomedical applications

Porous protein structures render biomaterials similar to their natural counterparts, extracellular matrices (ECMs), regarding both structure and material. Proteins in fibrous form have attracted considerable attention for fabrication of porous structures, as ECMs are composed of nanoscale protein fibers oriented randomly in three dimensions. Pores or voids created by random arrangements of the fibers provide spaces for cells to grow and spread. Fibrous structures could further facilitate cell attachment and guide cellular development and signaling. As technical difficulties have been gradually tackled, developing fibrous proteinous structures as biomaterials are arousing more interests. Micro- and nanofibrous structures have been developed from animal proteins, e.g., collagen, fibroin, keratin, and plant proteins, e.g., zein, soyprotein, and wheat gluten, via wet spinning, electrospinning, phase separation and other approaches. However, proteins as biomaterials usually suffer from inferior water stability, fast degradation, and poor mechanical properties. To circumvent these problems, crosslinking approaches have been applied, or synthetic polymers have been incorporated to improve the performance properties of proteins in aqueous environments.