Silk Nanococoons: Bio-Nanoreactors for Enzymatic Catalytic Reactions and Applications to Alcohol Intoxication.

Enzymatic reactions are often terminated by severe aqueous environments. Inspired by bio-protection of silk cocoons, a system of silk fibroin (SF) nanococoons is developed, which is capable of providing a bio-protective environment for enzymatic activities on one hand, and facilitating the process of cascade enzymatic reactions on the other hand. This gives rise to the significant enhancement in enzymatic stability and efficacy. For instance, the protected glucose oxidase and horseradish peroxidase enzymes exhibit a 17.5- and 7.0-fold increase when stored at 60 °C (>50% activity; ≈28 h) and 25 °C (>67.5% activity; ≈14 days), respectively, compared with free enzymes. It follows that this protective effect is subject to the mutual templated crystallization between enzymes and SF molecules, which prevents enzyme molecules from unfolding. In animal experiments, it shows that alcohol oxidase and catalase protected by silk nanococoons are able to reduce the alcohol levels of intoxicated mice with >5.0-time efficacy at the alcohol decomposition level of >80% in 4.0 h compared with the unprotected. By bio-inspiration of silk cocoons, the silk bio-nanoreactors demonstrate the significant potential applications in biomedicine.