A synergistic multiparametric MRI strategy for FAPα-targeted tumor fibrosis based on NaGdF4@PEG-FAPI nanoprobes.

Tumor-associated fibrosis, a key pathological feature of the tumor microenvironment (TME), is driven by cancer-associated fibroblasts (CAFs), promoting tumor progression and immune evasion, while fibroblast activation protein α (FAPα) overexpressed in over 90% of solid tumor stroma but absent in normal fibroblasts serves as an ideal target for early tumor diagnosis via fibrotic lesion detection. Herein, we developed a FAPα-targeted nanoprobe NaGdF4@PEG-FAPI for multiparametric MRI diagnosis of tumor fibrosis. This nanoprobe was engineered for dual-mode T1/T2 MRI, enabling comprehensive tumor characterization. Extensive biosafety evaluations confirmed its excellent biocompatibility. In A549 subcutaneous tumor models, NaGdF4@PEG-FAPI demonstrated superior performance. In Dynamic Contrast-Enhanced (DCE) sequence, it provided high-resolution visualization of the tumor vasculature, significantly outperforming both Gd-DTPA and the non-targeted control (NaGdF4@PEG-mal). Furthermore, the synergistic contrast bright enhancement in T1-weighted imaging (T1WI) and pronounced darkening in -weighted imaging () convergently and reliably confirmed tumor localization. The FAPI-mediated active targeting endowed the nanoprobe with prolonged tumor retention and enhanced signal intensity. NaGdF4@PEG-FAPI is highlighted as a robust and versatile platform in this study for multi-parameter, high-sensitivity tumor diagnosis.