Mixed zinc-iron oxide nanoparticles as therapeutic agents against biofilm-associated infections

Bacterial biofilms are a key contributor to antibiotic resistance and therapeutic failure, highlighting the urgent need for alternative treatment strategies. In this study, we investigate the potential of pure iron oxide nanoparticles (IONP) and mixed zinc-iron oxide nanoparticles (Zn-IONP) as nanoplatforms for targeting biofilm-associated infections caused by significant Gram-negative pathogens, specifically Pseudomonas aeruginosa and nontypeable Haemophilus influenzae . Zn-IONP with varying zinc content were synthesized and systematically characterized using DLS, ICP-OES, FTIR, and XRD, confirming the formation of stable, citrate-coated nanoparticles with a maghemite crystalline core. The antibiofilm performance of the nanoparticles was evaluated in vitro . While IONP showed negligible effects, Zn-IONP exhibited a significant, concentration-dependent inhibition of biofilm formation, achieving complete suppression in different strains of nontypeable H . influenzae at the highest concentrations. Importantly, Zn-IONP also demonstrated enhanced efficacy in the eradication of preformed biofilms in this pathogen, indicating their potential for both preventive and therapeutic applications. The toxicity studies revealed an overall acceptable biocompatibility profile, although Zn-IONP displayed moderately increased toxicity, potentially associated with reactive free-radical species generation. To assess in vivo behavior, Zn-IONP were successfully radiolabeled with 68 Ga and tracked using PET/CT imaging, showing predominant accumulation in the liver after intravenous administration. Collectively, these findings highlight the enhanced antibiofilm activity of mixed Zn-IONP and underscore their potential as a promising nanoplatform for the development of alternative therapies targeting biofilm-driven infections.