Structure-Chemical Modification Relationships with Silk Materials.

Chemical modifications used with silk materials can be challenging due to heterogeneous reactions, in part due to the assembly state of the protein chains. Here, we assess factors that determine the efficiency of chemical modifications with silk materials. Unlike other natural macromolecules, silk presents changeable self-assembled or aggregation states in aqueous solution, which affect the chemical reactions based on reactive group distribution or accessibility. To confirm this hypothesis, silk nanofibers in various conformation and aggregation states in solution were exposed to the same reaction conditions. Amorphous silk nanofibers provided improved control for consistent chemical modification outcomes, while silk nanofibers with control of structure could be utilized to generate bifunctional materials through multiple chemical modifications. The results of the chemical modifications demonstrated that control of the conformational transitions of silk nanofibers provided a feasible strategy for developing multifunctional silk materials with improved chemical outcomes.