Silk-Based Antimicrobial Polymers as a New Platform to Design Drug-Free Materials to Impede Microbial Infections

Surgical site infections (SSI) represent a serious health problem that occur after invasive surgery, thus new antimicrobial biomaterials able to prevent SSI are needed. Silks are natural biopolymers with excellent biocompatibility, low immunogenicity and controllable biodegradability. Spider silk-based materials can be bioengineered and functionalized with specific peptides, such as antimicrobial peptides, creating innovative polymers. Herein, we explored new drug-free multifunctional silk films with antimicrobial properties, specifically tailored to hamper microbial infections. Different spider silk domains derived from the dragline sequence of the spider Nephila clavipes (6mer and 15mer, 27 and 41 kDa proteins, respectively) were fused with the two antimicrobial peptides, Hepcidin (Hep) and Human Neutrophil peptide 1 (HNP1). The self-assembly features of the spider silk domains (β-sheets) were maintained after functionalization. The bioengineered 6mer-HNP1 protein demonstrated inhibitory effects against microbial pathogens. Silk-based films with 6mer-HNP1 and different contents of silk fibroin (SF) significantly reduced bacterial adhesion and biofilm formation, whereas higher bacterial counts were found on the films prepared with 6mer or SF alone. The silk-based films showed no cytotoxic effects on human foreskin fibroblasts. The positive cellular response, together with structural and antimicrobial properties, highlight the potential of these multifunctional silk-based films as new materials for preventing SSI.