Genetically engineered silk fibroin with antibacterial and antioxidant properties

Bombyx mori silk fibroin and the antimicrobial peptide cecropin B are promising biomolecules for biomedical applications due to their unique and complementary properties. In this study, we successfully expressed recombinant silk fibroin (R. fib) alone and in fusion with cecropin B (R. fib-cec) in Pichia pastoris, with yields of 6 mg/L for R. fib and 1.3 mg/L for the R. fib-cec fusion protein. Characterization of the proteins through SDS-PAGE, Western blotting, and MALDI-TOF confirmed the successful expression and purity of the recombinant proteins. Notably, the fusion protein exhibited potent broad-spectrum antibacterial activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, highlighting its potential as an antimicrobial agent. Furthermore, the R. fib and the R. fib-cec demonstrated significant protective effects against H₂O₂ and UVB-induced oxidative damage in human adult dermal fibroblast cells. Pretreatment with R. fib and R. fib-cec significantly improved cell viability and morphology. R. fib and R. fib-cec increased viable cell numbers in H₂O₂-treated cells (61.8% and 83.5%, respectively) compared to the control (33%), and in UVB-irradiated cells (67.7% and 87.3%, respectively) compared to the control (38%). Both proteins also significantly reduced LDH release, a marker of cell damage. These results demonstrate that R. fib, especially R. fib-cec, protects against oxidative stress-induced cellular damage, promoting cell proliferation and reducing cytotoxicity. These findings highlight the multifunctionality of the silk-cecropin B fusion protein, making it a promising candidate for diverse biomedical applications, including antimicrobial therapies, skin protection, and wound healing.

The online version contains supplementary material available at 10.1007/s13205-025-04293-7.