Hierarchical assembly of iron-oxide supraparticles for enhanced photothermal antibacterial activity

Bacterial infections, particularly those caused by drug-resistant strains, pose a significant global health threat. Photothermal therapy using iron-oxide nanoparticles shows promise in antibacterial treatments, but their use is limited by toxicity and nanoparticle agglomeration. This study presents a scalable spray-drying method to synthesize iron-oxide supraparticles, designed to enhance antibacterial efficacy while minimizing cytotoxicity. The iron-oxide supraparticles exhibited superior peroxidase-like activity compared to their nanoparticles, generating hydroxyl radicals through increased active sites. They demonstrated significant antibacterial activity against Escherichia coli and Staphylococcus aureus under near-infrared laser irradiation (1064 nm), achieving antibacterial rates of 77 % and 80 %, respectively, outperforming nanoparticles (25 % and 12 %). Their unique structure, with a larger diameter, rough surface, and internal porosity, contributed to improved antibacterial performance. Additionally, iron-oxide supraparticles maintained high cell viability in human dermal fibroblasts, confirming their biocompatibility. These supraparticles offer a promising approach for broad-spectrum antimicrobial applications without compromising host-cell viability. • First study innovating iron oxide supraparticles for antibacterial therapy. • Iron oxide supraparticles show superior antibacterial activity over nanoparticles. • Iron oxide supraparticles exhibit improved peroxidase activity and ROS generation. • Iron oxide supraparticles retain high biocompatibility for medical use.