<p>Biofilms pose a significant challenge to public health, fostering persistent infections that are notoriously difficult to eradicate. Their resilience stems partly from the inadequate penetration of conventional antibacterial agents into these structured microbial communities. To address this issue, we have developed a novel magnetite iron oxide Janus nanoparticles (JNPs), harnessing the magnetic field assistance for targeted biofilm elimination. In which, natural tannic acid (TA) and chitosan (CS) were coated on IONPs for improved antibacterial property and biocompatibility. Subsequently, the surfaces were functionalized with epoxy chloropropane and butanediamine, creating anchor points for the deposition of silver nanoparticles (AgNPs). Subsequently, AgNPs were embedded via an in situ reduction process, utilizing polyvinyl pyrrolidone (PVP) to precisely control the morphology of the Ag-armed magnetite JNPs. Remarkably, IONPs@BCS/Ag exhibited dual-responsive release characteristics, sensitively adjusting their Ag⁺ release in response to both oxygen levels and pH variations within the biofilms microenvironment. This system leveraged both stimulus-responsiveness and magnetic guidance to deliver exceptional antimicrobial performance against both planktonic bacteria and established biofilms. Critically, the superparamagnetic nature of IONPs@BCS/Ag enabled enhanced penetration into biofilms under an external magnetic field, facilitating the efficient delivery of AgNPs. Furthermore, the sustained release of Ag⁺ triggered by low pH and oxygen levels within the biofilm triggered the generation of reactive oxygen species (ROS), which not only accelerated the decomposition of the biofilm matrix but also disrupted the integrity of microbial communities. In summary, the IONPs@BCS/Ag magnetite JNPs, augmented by an external magnetic field, demonstrated enhanced anti-biofilm capabilities, offering immense potential as a potent weapon against biofilm-associated infections.</p> Graphical abstract <p></p>