An integrated preventive and therapeutic magnetic nanoparticle loaded with rhamnolipid and vancomycin for combating subgingival biofilms

Abstract

<h3>Objectives</h3><p>Mechanical debridement supplemented with antibacterial agents effectively eradicates subgingival biofilms formed in the periodontal pockets of severe periodontitis patients. However, the available antimicrobial agents have limited penetrating ability to kill the bacteria encased in the deep layers of biofilms. This study aimed to fabricate a novel magnetic nanoparticle (MNP) loaded with rhamnolipid (RL) and vancomycin (Vanc, Vanc/RL-Ag@Fe₃O₄) to combat subgingival biofilms.</p><h3>Methods</h3><p>The multispecies subgingival biofilm was formed by periodontal pathogens, including <em>Streptococcus oralis</em> (<em>S. oralis</em>), <em>Streptococcus sanguinis</em> (<em>S. sanguinis</em>), <em>Actinomyces naeslundii</em> (<em>A. naeslundii</em>), <em>Porphyromonas gingivalis</em> (<em>P. gingivalis</em>) and <em>Fusobacterium nucleatum</em> (<em>F. nucleatum</em>). Scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM), and quantitative real-time polymerase chain reaction (qRT-PCR) were used to determine the anti-biofilm efficacy of Vanc/RL-Ag@Fe₃O₄ with or without a magnetic field on multispecies subgingival biofilms.</p><h3>Results</h3><p>The minimal inhibitory concentration (MIC) values of Vanc/RL-Ag@Fe₃O₄ on <em>S. oralis</em>, <em>S. sanguinis</em>, <em>A. naeslundii</em>, <em>P. gingivalis</em>, and <em>F. nucleatum</em> were 25, 50, 100, 50, and 25 μg/mL, respectively. Vanc/RL-Ag@Fe₃O₄ (200 μg/mL) reduced the 7-d biofilm thickness from 22 to 13 µm by degrading extracellular polymeric substance (EPS) and killing most bacteria except for tolerant <em>F. nucleatum</em>. A magnetic field enhanced the anti-biofilm effect of Vanc/RL-Ag@Fe₃O₄ by facilitating its penetration into the bottom layers of biofilms and killing tolerant <em>F. nucleatum</em>.</p><h3>Significance</h3><p>Vanc/RL-Ag@Fe₃O₄ MNPs can release RL, Vanc, and Ag and eradicate subgingival biofilms by disrupting EPS and killing bacteria. Vanc/RL-Ag@Fe₃O₄ combined with a magnetic force is a promising approach for combating periodontal infection.</p>