Eco-friendly fabrication of durable antibacterial silk fabric via transglutaminase-catalyzed covalent immobilization of protamine.

The immobilization of antibacterial peptides (APs) onto silk material substrates remains challenging due to the scarcity of green, low-cost, and efficient methods for covalent bonding between these two proteins. The present work proposed a novel strategy for covalently grafting APs onto silk fiber surfaces for antibacterial purposes. Firstly, silk fiber surfaces were grafted with glutamine (Gln) through a cure-induced esterification reaction, the AP protamine (PM) was then covalently grafted via transglutaminase (TGase)-catalyzed cross-linking onto the fiber surfaces. FTIR, SEM, XPS investigations verified the successful attachment of PM and the covalent connection between the PM and the fiber surfaces. The modified silk fabric showed bacteria reduction rates higher than 99.99 % against S. aureus and E. coli, and maintained its antibacterial properties after 20 washing cycles, highlighting a desirable antibacterial activity and considerable durability. Moreover, the modifications did not sacrifice the appearances and wearing comfortabilities of silk fabric, but even led to significant enhancement in the moisture transfer properties. This strategy, based on naturally occurring amino acid, AP and enzyme, could not only be an attractive alternative for real-world application in the silk industry but also could be extended to the modification of other protein-based materials.