Multi-Mode Antibacterial Strategies Enabled by Gene-Transfection and Immunomodulatory Nanoparticles in 3D-Printed Scaffolds for Synergistic Exogenous and Endogenous Treatment of Infections.

As research on refractory Staphylococcus aureus-related implant infection intensifies, certain challenges remain, including low antibiotic concentrations within infected areas, immune escape achieved by intracellular bacteria, myeloid-derived suppressor cells (MDSCs) inducing regional immunosuppression, and recurrence of residual pathogenic bacteria after drug suspension. Herein, a novel antimicrobial system to simultaneously address these issues is proposed. Specifically, an oxygen-species-responsive 3D-printed scaffold with shell-core nanoparticles is designed, which are loaded with an antimicrobial peptide plasmid (LL37 plasmid) and have LL37 grafted on their surface (LL37@ZIF8-LL37). The surface-grafted LL37 directly kills S. aureus and, following entry into cells, the nanoparticles kill intracellular bacteria. Moreover, in vitro and in vivo, following translation of the LL37 plasmid, cells function as factories of the antimicrobial peptide, thereby generating a continuous, prolonged antibacterial effect at the site of infection. This system significantly reduces the abnormal increase in MDSCs within the infected microenvironment, thus relieving the immunosuppressive state and restoring a protective antimicrobial immune response. Hence, this proposed antimicrobial system provides an antimicrobial immune response and a novel strategy for S. aureus-related infections by offering a combined active antimicrobial and immunotherapeutic strategy, thereby significantly reducing the recurrence rate following recovery from implant-associated infections.