Integrated manganese (III)-doped nanosystem for optimizing photothermal ablation: Amplifying hyperthermia-induced STING pathway and enhancing antitumor immunity.

Despite the great promise initially demonstrated by photothermal ablation (PTA) therapy, its inability to completely ablate large tumors is problematic, because this has been found to result in residual tumors at ablation margins and bring a relative high rate of subsequent recurrences and metastases. To address this issue, we herein report a smart photothermal nanosystem (PBM) based on FDA-approved Prussian blue (PB) nanoparticles, doped with Mn (III) to suppress the tumor debris left by incomplete ablation. Notably, our study demonstrated that PTA-induced hyperthermia plays a crucial role in initiating the cGAS-STING pathway by generating damaged cytosolic DNA. This PBM nanosystem, which consumes glutathione and continuously releases Mn(II), further amplifies the PTA-induced cGAS-STING pathway in CT26 colon and 4T1 breast tumor models. Moreover, treatment with PBM following PTA boosted the robust immune response in situ and extended to the whole body with a remarkable suppression effect on both local residual and distant tumors. This work, which improves the antitumor efficacy of nonablated areas utilizing hyperthermia-enhanced immune therapy, may therefore provide a promising adjuvant antitumor strategy for the issue of incomplete ablation. STATEMENT OF SIGNIFICANCE: This work discovered, for the first time, that photothermal ablation-induced hyperthermia plays a crucial role in initiating the cGAS-STING pathway. Taking advantage of this finding, we developed a smart photothermal material (PBM) tailored for incomplete tumor ablation. This integrated Mn(III)-doped nanosystem (PBM) demonstrated superior therapeutic benefits due to the thermal ablation process and immune enhancement. As the photothermal ablation-induced cGAS-STING pathway was triggered, the released Mn(III) consumes GSH while continuously transferred to Mn(II), which further amplified STING activation and facilitated a more robust antitumor immunity, thereby remarkably inhibiting both local residual and distant tumors in virtue of the biological changes under thermal ablation.

Development of a Novel MR Colonography via Iron-Based Solid Lipid Nanoparticles.

PURPOSE: To develop an iron-based solid lipid nanoparticle (SLN) absorbable by the intestinal wall and assess the differential diagnostic value of intestinal lesions in magnetic resonance imaging (MRI). METHODS: SLNs were prepared with the simultaneous loading of trivalent Fe ions (Fe3+), levodopa methyl ester (DM), and fluorescein isothiocyanate (FITC). We evaluated the particle size, loading rate, encapsulation efficiency, and cytotoxicity of SLNs. The T1 contrast effects of the FeDM-FITC-SLNs and gadolinium-based contrast agent (GBCA) were compared in different mouse models: acute ulcerative colitis (AUC), chronic ulcerative colitis (CUC), colon adenocarcinoma (COAD), and normal control. MRI was performed in the same mouse with intravenous injection of GBCA on day 1 and enema of FeDM-FITC-SLNs on day 2. The signal-to-noise ratios (SNRs) were compared using one-way analysis of variance. Tissues were then collected for histology. RESULTS: The average particle size of FeDM-FITC-SLN was 220 nm. The mean FeDM loading rate was 94.3%, and the encapsulation efficiency was 60.3%. The relaxivity was 4.02 mM-1·s-1. After enema with FeDM-FITC-SLNs, MRI showed the following contrast enhancement duration: AUC = COAD > normal > CUC. Confocal fluorescence microscopy confirmed that FeDM-FITC-SLNs were mainly distributed in the intestinal mucosa and tumor capsule. CONCLUSION: Iron-based SLNs are promising alternatives for contrast enhancement at T1-weighted MRI and will help in the differential diagnosis of intestinal bowel diseases (IBDs).