Tuning the conformation and mechanical properties of silk fibroin hydrogels

Mechanical properties of biomaterials play an important role in their biological performance. Among the most important parameters in designing of biomaterials, their structure and conformation strongly affect their mechanical properties as well as cell adhesion, proliferation, and differentiation. Silk fibroin (SF), extracted from Bombyx mori cocoons, has attracted a lot of scientific interest in the past years as a natural biomaterial due to its exceptional host tissues response, appropriate mechanical properties, tunable degradation, simple processing method and low cost. The formation of beta-sheets in the structure of SF enhances its mechanical properties. In recent years, several studies have focused on tuning the mechanical properties of SF for biomedical applications by inducing the formation of beta-sheets. Some treatment methods have been introduced to alter SF structure and improve its mechanical properties. Chemical, physical and enzymatic crosslinking, water and alcoholic treatments and irradiations have been recommended as methods to inducing beta-sheets conformation in SF structure. Several studies have developed these methods by adding suitable components and changing the concentration, temperature, humidity, pH, and various other parameters. In this review, we focus on the treatment methods, which result in the conformational transition of SF and tuning its mechanical properties.