Reprogramming M2 macrophages via TLR7/8 agonist-loaded hollow MnO2 nanovehicles to suppress the progression of liver cancer

As a prevalent malignancy, liver cancer ranks as the third most common cause of cancer mortality globally. Within the tumor microenvironment, tumor-associated macrophages (TAMs) exhibit contrasting functional phenotypes: the anti-tumor M1 type and the pro-tumor M2 type. Reprogramming TAMs from the M2 to the M1 phenotype has emerged as a promising immunotherapeutic strategy. Here, we engineered a multi-nano therapeutic system, PAH@HMMDN@R848, by loading a TLR7/8 agonist (R848) onto hollow MnO2 nanoparticles (HMMDN) and coating with polyallylamine hydrochloride (PAH). In vitro, this system efficiently repolarized M2 macrophages to the M1 phenotype, evidenced by decreased CD206, Arg-1, IL-10 and increased CD80, iNOS, TNF-α (P < 0.05). Under acidic/glutathione-rich conditions, HMMDN degraded to release Mn2+, which served as a T1-weighted MRI contrast agent with a high relaxivity (r1 = 5.255 mM-1 s -1). Mechanistically, PAH@HMMDN@R848 activated both NF-κB (via R848) and STING (via Mn2+) pathways, leading to synergistic M1 polarization. In a subcutaneous H22 liver cancer mouse model, intratumoral injection of PAH@HMMDN@R848 significantly suppressed tumor growth (tumor inhibition rate 80.6%) without obvious systemic toxicity. Immunohistochemistry and cytokine analysis revealed that the treatment increased M1 macrophage infiltration (CD80+) and reduced M2 macrophages (CD206+) within tumors, along with elevated TNF-α/iNOS and decreased IL-10/Arg-1. This study presents a multifunctional nanoplatform capable of TAMs reprogramming and MRI diagnosis, offering a promising approach for liver cancer theranostics.