An Antimicrobial, Cell-Adhesive, and Growth Factor-Producing Living Material Engineered From Bacillus subtilis Biofilms for Wound Healing.

Chronic wounds represent a burden for healthcare systems and critically impair quality of life of patients. Engineered living materials (ELMs) show great potential as scaffolds and delivery systems in tissue regeneration. As a generally regarded safe biofilm-producing organism, Bacillus subtilis (B. subtilis) presents interesting properties to develop functional ELMs in biomedicine. In this study, we engineer B. subtilis to design a protein-based living matrix eluting bioactive sequences for wound healing. Accordingly, we create a biofilm-deficient B. subtilis strain that expressed the biofilm scaffold protein, TasA in fusion with a cell-adhesive motif (TasA-PRb), which results in biofilms with cell-adhesive properties for fibroblasts and keratinocytes. Besides, B. subtilis is known to elicit antimicrobial properties against strains of E. coli and S. epidermidis, which are not impeded by biofilm engineering. We also incorporate secretion of fibroblast growth factor 2 (FGF2), known to promote wound healing, in the biofilm-deficient strain. Co-culture of FGF2-expressing and TasA-PRb producing strains resulted in biofilms secreting bioactive FGF2. Chronic wound healing assays in diabetic mice reveal accelerated wound closure in mice treated with the TasA-PRb/FGF2 biofilms, with absence of observable adverse effects. This underlines the potential of the B. subtilis biofilm for the design of functional ELMs in biomedicine.