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Fluorinated Gadolinium Chelate-Grafted Nanoconjugates for Contrast-Enhanced T1-Weighted 1H and pH-Activatable 19F Dual-Modal MRI.

Magnetic resonance imaging (MRI) is one of the most popular imaging techniques, which offers an ionization-free noninvasive means for imaging deep tissues with high resolution. Conventional 1H MRI is well versed in providing detailed anatomical information but suffers from low contrast for tracking biomarkers because of the abundance of water in living bodies. 19F MRI with negligible endogenous background interference enables highly sensitive detection of biomolecular targets and has drawn extensive attention from the biomedical research community recently. However, this imaging technique only acquires the "hot spot" signals of exogenous 19F nucleus-containing imaging probes. 1H/19F MRI dual-modal imaging is expected to compensate for the limitations of either single-modal imaging and accomplish synergistic morphological and physiological imaging. Herein, we report a highly biocompatible nanoconjugate composed of pH-responsive 19F nucleus-bearing Gd3+ chelates, which enables significant contrast enhancement for T1-weighted 1H MRI and permits pH-responsive activation of 19F signals for 19F MRI, providing both clear anatomical details of living bodies and the biorelevant molecular information with low background interference. This nanoconjugate facilitates sensitive and accurate detection of tumors with contrast-enhanced T1-weighted 1H and pH-activatable 19F dual-modal imaging on a single MRI scanner.