Silk fibroin-based scaffolds functionalized with bacteriophages exhibit substantial antimicrobial potential

Abstract

Bacterial infections brought on by biofilms are the most common health concern in injuries, food industries among others, therefore, composite scaffolds that possess antibacterial characteristics are desirable. Herein, we developed a phage functionalized silk fibroin-based scaffold through surface charge modification of the composite scaffold with polyethyleimine (PEI). This was aimed at assessing the antibacterial efficiency of the composite scaffold against the host strain Bacillus subtilis, which would ultimately serve as a model approach for the design of diverse antibacterial biomaterials. The SF scaffold was initially formed through the direct freeze-thaw method, prior to polymerization with PEI and AR9 phage functionalization of the PEI polymerized Scaffolds by incubating with phage lysate. PEI exhibits antibacterial properties against both Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria, although it is significantly cytotoxic. To develop a biocompatible AR9 phage delivery scaffold with effective antibacterial properties against Bacillus subtilis, we modified the surface of a silk fibroin scaffold with PEI, resulting in a highly charged silk fibroin scaffold via use of low molecular weight PEI and concentration-based optimization of scaffold polymerization with PEI. The morphological and physiochemical properties of formed scaffold were assessed through Raman and Fourier infrared spectroscopy, while the antibacterial assays were done through growth inhibition zones/cell viability assays. The polymerized phage scaffold SF20_PEI.AR9 possessed the highest antimicrobial effect with clear inhibition zones of about 7.8 mm compared to about1.8 mm for the PEI polymerized scaffold (SF20_PEI) due to the lytic effect of surface attached phages on the bacterial cells thus underscoring significant effect of PEI polymerization in stabilizing AR9 phage attachment on the scaffolds. This direct polymerization approach achieved significant stabilization of the phages in the biomaterial mainly due to minimal alteration of the PEI architecture and thus could serve as a model for future development of phage functionalized scaffolds.