Superhydrophilic Fluorinated Polymer Probe for Zero-Background 19F MRI with Adaptable Targeting Ability.

19F magnetic resonance imaging (19F MRI), with zero background, high tissue penetration depth, excellent spatial resolution, and nonradioactive features, has attracted considerable attention but faces tough challenges due to the shortage of sensitive and selective targetable probes. Herein, we report a biocompatible and highly sensitive 19F MRI probe with an adaptable tumor-targeting ability. The fluorine-grafted polymer (PIBMA-FSON) probes were rich with sulfoxide and carboxy groups, containing a high fluorine content (∼17 wt %). The probes exhibit superhydrophilicity, strong 19F MRI signals (enhancement of ∼95-fold), long transverse relaxation time (T2, 422 ms), and excellent 19F MRI capability. Conjugation using a targeting peptide (Arg-Gly-Asp, RGD) afforded ultrasmall soft polymer probes (PIBMA-FSON-RGD) with superhydrophilicity and tumor-targeting ability suitable for the 19F MRI of orthotopic bladder cancer. Amidification of 5% of the carboxylate units with oleylamine resulted in PIBMAOAm-FSON nanoprobes (NPs) via self-assembly, displaying different targeting toward subcutaneous tumors. Further grafting with near-infrared (NIR) dyes renders the probe suitable for NIR-fluorescence and 19F MRI dual-modality imaging. This study provides a suitable approach for designing highly sensitive and zero-background 19F MRI probes with a tunable tumor-targeting ability.