Silk Sponges With Surface Antimicrobial Activity

The development of robust scaffolds with an inherent antimicrobial property is important for a range of biomedical applications, such as wound healing. In this study, we report the facile fabrication of porous silk scaffolds/sponges with inherent surface antimicrobial properties. Silk sponges are structurally robust, biocompatible, and biodegradable and hence serve as an excellent substrate material for wound healing purposes. Here, silk sponges were surface-functionalized via layer-by-layer assembly based on electrostatic interactions using a combination of synthetic cationic antimicrobial polymers (that mimic antimicrobial peptides) and anionic sodium alginate. The antimicrobial films on the silk surface are stable and nonleaching, as verified by the fluorescence measurement and colony forming unit (CFU) analysis. Exposure of the antimicrobial silk sponges to bacteria culture solutions (ca. 10(8) CFU mL(-1)) over 1 h yielded 1 to 4 log(10) reduction in bacteria cell viability depending on the bacteria type (Gram-negative or Gram-positive) and the combination of antimicrobial polymers used, as confirmed by CFU analysis. The silk substrate coupled with the efficient immobilization of antimicrobial polymers thus provides a versatile platform for the generation of potential wound healing devices.