Near-Infrared-Responsive Bi2Fe4O9/rGO nanocomposite for intravesical antibacterial photodynamic therapy of urinary tract infections.

Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) are common and prone to recurrence. Increasing antibiotic resistance and systemic toxicity compromise the efficacy of conventional UTI therapies. Antibacterial photodynamic therapy (aPDT) uses light-activated photosensitizers to produce bactericidal reactive oxygen species (ROS) and offers a non-antibiotic strategy for localized treatment. Here, we developed a near-infrared (NIR)-responsive Bi2Fe4O9/reduced graphene oxide (BFO/rGO) nanocomposite optimized for intravesical aPDT. Within the composite, orthorhombic Bi2Fe4O9 (BFO) formed ultrathin nanoplates on graphene and showed enhanced absorption at 808 nm NIR. The presence of rGO further suppressed electron-hole recombination compared with pristine BFO, improving charge separation for photodynamic activity. Under NIR irradiation, BFO/rGO generated abundant ROS, which in turn led to significant bacterial inactivation. In vitro, BFO/rGO showed acceptable cytocompatibility at 80 μg mL-1 while significantly reducing UPEC viability. In vivo, intravesical BFO/rGO combined with NIR irradiation effectively reduced bacterial loads in the bladder and kidney and preserved urothelial integrity in a murine UTI model. These findings highlight BFO/rGO as an NIR-activated nanocomposite that is compatible with urothelial and renal tissues and has potential for localized photodynamic control of urinary pathogens while reducing reliance on antibiotics.