Photothermal-Immunomodulatory Nanohydrogel Eradicates Infection and Accelerates Bone Regeneration in Infected Defects

The management of infected bone defects remains difficult due to the dual challenges of stubborn infection and impaired regeneration. To overcome these issues, a multifunctional nanocomposite hydrogel (PNPs@RuO₂@HAP@Gel) is created by combining photothermal/antioxidant-responsive polymer nanoparticles (PNPs@RuO₂) with bioactive nano-hydroxyapatite (HAP). When exposed to a second near-infrared (NIR-II) laser, the hydrogel showed strong photothermal antibacterial effects by damaging bacterial membranes and disrupting metabolic functions. The ruthenium oxide (RuO₂) component scavenged reactive oxygen species, helping to modulate the immune microenvironment, while the hydrogel matrix acted as a bioactive scaffold, encouraging osteoblast adhesion and growth. In a rat model with infected bone defects, the hydrogel proved to be highly antimicrobial, lowered pro-inflammatory cytokines, and supported osteogenic differentiation, aiding in the formation of new bone and blood vessels. This dual-function system combines targeted antibacterial action with support for regeneration, offering a promising treatment strategy for infected bone defects.