Sensitive Multichannel ¹⁹F Magnetic Resonance Imaging Enabled by Paramagnetic Fluorinated Ionic Liquid-Based Probes

Area of Science:

• Biomedical Imaging
• Materials Science
• Radiochemistry

Background:

• Fluorine-19 magnetic resonance imaging (MRI) offers advantages over proton MRI due to its low biological background and high sensitivity.
• Fluorinated ionic liquids (FILs) are promising 19F sources for MRI probes due to solubility and high fluorine content.
• The effectiveness of FIL-based probes is limited by suboptimal 19F relaxation times (T1 and T2).

Purpose of the Study:

• To develop a strategy for modulating 19F relaxation times in FILs to enhance their MRI imaging capacity.
• To create high-performance 19F MRI probes using FILs and paramagnetic Mn2+ ions.
• To demonstrate the feasibility of using relaxation modulation for advanced 19F MRI applications.

Main Methods:

• Exploited the paramagnetic relaxation enhancement effect of Mn2+ ions to tune the T1 and T2 relaxation times of three FILs (EMIMBF4, BMIMOTf, BMIMPF6).
• Optimized Mn2+ concentrations to achieve significant signal enhancement.
• Encapsulated FILs and Mn2+ ions within liposils to create stable 19F MRI probes for in vivo studies.

Main Results:

• Achieved over 5-fold signal enhancement in FILs by modulating 19F relaxation times with Mn2+ ions.
• Constructed liposil-encapsulated FIL-Mn2+ probes enabling fast and clear in vivo 19F MRI.
• Validated the capacity for multiplexed 19F MRI using a probe containing multiple FILs and Mn2+.

Conclusions:

• Paramagnetic FIL-based probes show significant potential for in vivo "hot spot" 19F MRI.
• Relaxation time modulation is a feasible and effective strategy for developing high-performance 19F MRI probes.
• This approach advances the application of 19F MRI in biomedical research and clinical diagnostics.