Multiresponsive Nanoprobes for Turn-On Fluorescence/¹⁹F MRI Dual-Modal Imaging

Multiresponsive nanoprobes are highly desirable for low background and highly sensitive imaging in biomedical applications. Herein, we design a glutathione (GSH)/pH dual-responsive nanoprobe capable of both fluorescence imaging in cells and ¹⁹F magnetic resonance imaging (¹⁹F MRI) in deep tissue, by encapsulating manganese oleate (Mn­(OA)₂) on the surface of fluorinated fluorescent quantum dots (F-ZnS:Mn²⁺). In this approach, Mn­(OA)₂ serves as an efficient quencher of both fluorescence and ¹⁹F MRI signal. Both the fluorescence and ¹⁹F MRI signal can be turned on by introducing glutathione (GSH) that breaks up the Mn–O bonds within Mn­(OA)₂ under weak acidity conditions (e.g., pH 6.0). The imaging results in cells and mice suggest that this novel strategy can offer a promising nanoprobe for turn-on fluorescence/¹⁹F MRI dual-modal tumor imaging.