The subsequent magnetic heating-promoted Fenton reaction catalysed by the iron ions released from the MRT nanoparticles disintegrates bacterial biofilms via in situ oxidative damage, leading to significant LPS release from the damaged bacteria, which acts as immunogenic PAMPs to activate antitumor immunity, including innate macrophage polarization into antitumor M1 phenotype and maturation of DCs via the TLR4–MyD88–NF-κB pathway and the consequent adaptive T effector cells awakening, finally achieving excellent antitumor immunotherapeutic efficacy in the orthotopic CRC mice model. Here, TLR4 is linked to colorectal carcinoma.