Abstract
Recent works by Tansil et al. suggested a promising way to introduce functionalities into silk fibroin by simply feeding, which was expected to allow silk-based functional biomaterials to have scalable production and direct application. In this research, we aimed to obtain deeper understanding on such a smart strategy of selectively absorbing additives via molecular recognition and the impact of additives on the secondary structures of fibroin. We suggested that the partition ratio of the additive in fibroin and sericin was a critical parameter to evaluate the ability of the additive to enter fibroin, which showed a strong correlation with the isoelectric point (pI) of the additive. On the basis of the classical micelle model, we suggested that silk in vivo recognized additives with low pI and amphiphile chemical structure from other chemical similar additives and assembled them into fibroin. Fibroin-additive assemblies were rather stable that hindered the formation of β-sheet and also crystallites, as indicated by FTIR and WAXD.