Novel Applications of Silk Proteins Based on Their Interactions with Metal Ions

Silk secreted by Bombyx mori L. silkworm has become one of the most important biomaterials, due to its excellent biocompatibility, controllable biodegradability, superior processability, and unique mechanical properties. Silk fibroin and sericin, as the two components of silk, contain abundant polar functional groups, and thus can bind metal ions through electrostatic interaction and chelation. Based on this binding, silk proteins not only can be used to fabricate ecofriendly and efficient adsorbents to remove heavy metals from waterbodies, but also can synthesize metal nanostructures (nanoparticles or nanoclusters) to form silk/metal composites with amazing optical or electrochemical characteristics. This binding also can be manipulated to optimize silk's performance. This review focuses on discussing and summarizing advances in the use of silk fibroin and sericin for heavy metal ion-contaminated water remediation, biosensing materials, and electrochemical materials from the perspective of the interaction between silk proteins and metal ions. The performance enhancement of silk using metal ions is also analyzed. Moreover, the silk proteins' interactions with metal ions and related structural features that contribute to the above sustainable applications are illustrated to lay a theoretical foundation. This review will favor the expansion of the applications of silk in both the traditional textile field and new biomaterials.