Magnetic-controlled dandelion-like nanocatalytic swarm for targeted biofilm elimination

Infections caused by drug-resistant strains pose a serious threat to human health. Most bacterial infections are related to biofilms. The generation of a bacterial biofilm greatly reduces the antibacterial efficiency of antibiotics and some traditional antibacterial drugs, and it is very important to develop antibacterial drugs to replace antibiotics. Here, encouraged by the promising magnetic control technology of micro/nanorobots, the synergistic antibacterial strategy of a dandelion-like magnetically-controlled multifunctional hierarchical magnetic biomimetic nanozyme, Fe₃O₄@SiO₂@dendritic mesoporous silica@small-Fe₃O₄ nanoparticles (FSDMSsF NPs), was developed to be effective against bacterial biofilms. FSDMSsF NPs showed great magnetic properties and peroxidase-like activities, and could act as catalytic carriers for the production of hydroxyl radicals that are highly toxic to bacteria in a low-concentration H₂O₂ environment, killing planktonic bacteria. The antibacterial rate of FSDMSsF NPs reached 99.5% at a concentration of 200 μg mL^-1. The synergistic antibacterial mechanisms of the mechanical factor and the chemical factor are further discussed. Under time-varying magnetic swarm control, the antibacterial performance of FSDMSsF NPs against bacteria was significantly improved. On this basis, the elimination effect of FSDMSsF NPs on bacterial biofilms is further discussed. The results showed that FSDMSsF NPs could target and eliminate biofilms through complex channels under the control of magnetic fields. In addition, the system could remove biofilms in occlusions by changing the morphology and movement mode of an FSDMSsF NP swarm under magnetic field control. The current work proposes a facile and physical-chemical synergistic strategy for effective antibacterial therapy. FSDMSsF NPs could effectively kill planktonic bacteria and remove stubborn biofilms through magnetic field guidance, achieving thorough antibacterial efficacy, which has great potential in the treatment of drug-resistant bacterial infections.