A bioinspired dual-crosslinked tough silk protein hydrogel as a protective biocatalytic matrix for carbon sequestration

The development of carbonic anhydrase (CA)-based materials for the environment-friendly sequestration of carbon dioxide (CO₂) under mild conditions would be highly valuable for controlling emissions to the environment and for producing value-added chemicals. Here, a highly tough and stable CA-encapsulating silk protein hydrogel was developed as a robust biocatalyst for CO₂ sequestration through a bioinspired dual-crosslinking strategy that employed photoinduced dityrosine chemical crosslinking followed by dehydration-mediated physical crosslinking. The target enzyme was efficiently encapsulated in the silk hydrogel with ~ 60% retention of the activity of free CA, and the encapsulated CA exhibited excellent overall multi-use, storage and thermal stabilities. The dual-crosslinked CA-encapsulating silk hydrogel exhibited a significant compressive modulus, which surpassed the moduli of most traditional and double-network hydrogels as well as those of enzyme-encapsulated hydrogels. This hydrogel also showed high resiliency and elasticity and outstanding structural stability. Importantly, the dual-crosslinked CA-encapsulating silk hydrogel facilitated the sequestration of CO₂ into calcium carbonate with high CO₂ hydration activity. Thus, the unique combination of bioinspired dual-crosslinking with silk fibroin protein and CA enzyme demonstrates the successful application of this protein hydrogel as a promising biocatalyst for CO₂ sequestration by showing high activity, strong mechanical properties and outstanding structural stability.