Bacteriophage Cocktail in Hydrogel Dressing Modulates Macrophage Responses and Induces Skin Cell Migration

Bacteriophage mixtures have been explored as biomaterials to promote tissue repair. In this study, we tested the hypothesis that incorporating a phage mixture into a wound dressing could modulate immune cell responses and skin cell migration within the wound environment.

Phage strains specific to three common bacterial pathogens-Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa-were embedded in an alginate hydrogel (E-Alg) or grafted onto its surface (S-Alg). The viability of the phages released from the samples were tested. 3T3 fibroblasts in a transwell system were co-cultured with Raw 264.7 macrophages seeded on the dressing samples containing the phage mixture. The cytokine release and fibroblast migration through the transwell membrane were measured.

The phages remained lytic to their hosts after incorporation in the dressing samples (p < 0.001). Macrophages internalized similar numbers of phages, regardless of whether they were stimulated with lipopolysaccharide (LPS) or not (p > 0.05). In the presence of the phage mixture, the resting macrophage produced significantly more nitric oxide (NO), interleukin 1ß (IL-1ß) and tumor necrosis factor α (TNF-α) (p < 0.001). In contrast, the phage mixture significantly reduced the production of these inflammatory mediators in LPS-stimulated macrophages (p < 0.001). The numbers of fibroblast migrating through the membrane toward the macrophages positively correlated with the concentrations of TNF-α and IL-10 released by the macrophages.

A nonhealing wound-common in diabetic patients-is often a result of weakened immune responses. A phage-releasing dressing may not only alleviate bacterial infection but also attract and stimulate immune responses that promote skin repair.