Hierarchically Porous Silver–Carbon Composite with Dialyzable Silver Release for Biofilm Control and Healing of Infected Wounds

Abstract

Biofilm-associated wound infections require antibacterial materials that can control attached bacteria while limiting excessive silver exposure. In this study, we prepared a sponge-like hierarchical porous silver–carbon material through in situ glucose foaming and carbonization. The material had a Brunauer–Emmett–Teller surface area of 1067.8 m² g^–1 and a total silver content of 9.22% by weight after complete digestion. During dialysis against phosphate-buffered saline containing 1% bovine serum albumin, the material released approximately 0.27% of its total silver over 72 h. Comparative results showed differences in pore structure and silver transport but did not link release to a specific pore class. The porous silver–carbon material inhibited Escherichia coli and Staphylococcus aureus. The minimum inhibitory and bactericidal concentrations were 4 and 8 μg mL^–1, respectively, for Escherichia coli and 8 and 16 μg mL^–1, respectively, for Staphylococcus aureus. Propidium iodide staining and scanning electron microscopy were consistent with increased membrane permeability and cell-surface damage. Assays using 2′,7′-dichlorodihydrofluorescein diacetate and electron spin resonance measurements supported reactive oxygen species-related stress. Plate-counting assays showed concentration-dependent inhibition of biofilm formation and reduced viable bacterial recovery from established biofilms. Murine fibroblast viability remained above 95%, and hemolysis remained below 5% under the tested conditions. In a full-thickness mouse wound model infected with Escherichia coli, the material and silver nitrate were applied at equal elemental silver doses of approximately 35 μg per wound. The material treatment yielded lower wound-derived colony counts per plate than the silver nitrate treatment on day 4 and reached approximately 95% wound closure by day 14. Endpoint histology showed no obvious structural abnormalities in the examined major organs. These findings suggest that pore structure, dialyzable-silver transport, and bacteria-material interactions should be considered together when designing porous silver–carbon antibacterial materials.