Fe₃O₄-Based Nanospheres with High Photothermal Conversion Efficiency for Dual-Effect and Mild Biofilm Eradication against Periodontitis

Periodontitis, a chronic inflammatory oral disease resulting from plaque biofilms, affects about 743 million individuals worldwide. However, the efficacy of current treatments is hampered by challenges in delivering antibiotics to recalcitrant oral biofilms and bacterial resistance, thereby impeding successful treatment of infectious diseases. To address the issues, an antibacterial photothermal material was designed, comprising a spherical structure of zinc oxide (ZnO) wrapped with triiron tetraoxide (Fe₃O₄). The outer layer of the material adsorbed epsilon-polylysine (EPL) by electrostatic action, ultimately leading to the fabrication of Fe₃O₄/ZnO/EPL nanoparticles (FZE NPs). The Fe₃O₄ core endowed the nanoparticles with efficient photothermal properties, facilitating the dispersion of dense biofilms, which dramatically promoted the adsorption and penetration of ZnO and EPL into the biofilms to effectively kill bacteria in biofilms <i>in vitro</i> with enhanced sterilization ability. Additionally, upon dissolution in aqueous media, EPL acts as a positively charged antimicrobial peptide that adsorbs onto the surface of negatively charged bacterial membranes, thereby effectively modulating inflammatory responses. In order to ascertain the efficacy of FZE NPs, an investigation was conducted into their antimicrobial effects against the periodontitis-associated pathogen <i>Porphyromonas gingivalis</i> (<i>P. gingivalis</i>) <i>in vitro</i>. Furthermore, the antiperiodontitis potential of FZE NPs was evaluated in Sprague-Dawley (SD) rats of ligamentous periodontitis. In addition, toxicity evaluations indicated that the material had an acceptable biosafety profile <i>in vitro</i> and <i>in vivo</i>. In summary, the nanospheres (FZE NPs) represent a promising therapeutic strategy for the treatment of periodontitis.