Antimicrobial Recombinant Spider Silk

Overview

Surgical site infection (SSI) from sutures has become a major global health emergency as a result of the rise in antibiotic resistance. Methicillin-resistant S. aureus and other pathogenic strains are difficult to treat with antibiotics, so drug-free sutures with antimicrobial properties could provide a solution. Functionalized spider silk protein (spidroin) has extraordinary strength due to its large repetitive region (150Rep) that forms crosslinked beta-sheets and fiber-forming ability due to coagulating terminal regions (NT & CT), and is therefore a great candidate. In this project the properties of antimicrobial peptide Human Neutrophil Defensin 1 (HNP-1) and spidroin were combined to create an antimicrobial silk using a novel method. Ni-NTA purified (6His-)2Rep-HNP1 fusion protein was mixed with recombinant (6xHis-)NT2RepCT spidroin at 1:25, 1:20, 1:10 ratios, and spun into silk fibers by syringe-pumping protein into a 100% isopropanol bath. Beta-sheet crosslinking of the identical 2Rep regions “tagged” the 2Rep-HNP1 permanently onto the resultant silk. Silk showed no sign of degradation if left in PBS, EtOH, or after autoclaving. The tagged 2Rep-HNP1 retained over 90% of its broad-spectrum antimicrobial activity against S. aureus and E. coli as measured by log reduction. Furthermore, a modified expression protocol increased protein yield of NT2RepCT 2.8-fold, and variable testing of the spinning process demonstrated the industrial viability of silk production. The experiment confirmed the hypothesis and presents a suture alternative: antimicrobial recombinant spider silk.