3D-printed Bdellovibrio bacteriovorus hydrogel for treatment of infected combined radiation and burn injury

Combined radiation and burn injury (CRBI) is induced by simultaneous or sequential ionizing radiation damage and skin burns. CRBI weakens the immune ability, leading to drug-resistant bacterial infections and delayed wound healing. Bdellovibrio-and-like organisms (BALO) are naturally predatory bacterium that can prey on most Gram-negative bacteria by entering the periplasmic space of their prey and degrading the biomolecules of host cells. In this study, we combined gelatin, calcium alginate, and activated BALO water samples to form bio-inks to three-dimensional (3D)-print BALO-loaded hydrogels (TDBG) for the treatment of CRBI combined with multidrug-resistant Acinetobacter baumannii (MRAB) infection. The freeze-dried 3D-printed hydrogel exhibited a 3D network structure attached with gelatin films, and owned good printability and biocompatibility. The printability improved adaptation to wound shapes for the personalized treatment of infected wounds. The 3D network structure allowed the surviving and motion of BALO, favoring its high predatory activity. All animal experiments were approved by the Ethics Committee of Academy of Military Medical Sciences, and the experiments were conducted in accordance with relevant guidelines and regulations (approval number: IACUC-DWZX-2022-834). TDBG treatment improved wound healing by accelerating the mouse wound closure rate of CRBI combined with MRAB infection, reducing the expression of pro-inflammatory cytokines in the wound tissues, and increasing collagen deposition. This study expands the application scope of live biological products and provides a basis for their development and clinical applications.