An Fe complex for ¹⁹F magnetic resonance-based reversible redox sensing and multicolor imaging

Area of Science:

• Chemical Biology
• Biomedical Imaging
• Fluorine Chemistry

Background:

• Developing responsive contrast agents for magnetic resonance imaging (MRI) is crucial for disease detection.
• Fluorine-19 (19F) MRI offers high sensitivity and a low background signal, making it suitable for targeted imaging.
• Responsive agents that change their signal based on biological conditions can provide valuable diagnostic information.

Purpose of the Study:

• To develop a first-in-class responsive 19F MRI agent utilizing a pentafluorosulfanyl (-SF5) tag.
• To demonstrate the agent's ability to detect reducing environments via an iron redox couple.
• To showcase the potential for multicolor imaging by combining this agent with other fluorinated probes.

Main Methods:

• Synthesis of a novel pentafluorosulfanyl (-SF5)-tagged 19F MRI agent.
• Investigation of the agent's response to reducing and oxidizing conditions using an Fe(II/III) redox couple.
• Evaluation of signal changes in 19F MRI upon interaction with cysteine.
• Demonstration of simultaneous multicolor imaging with a trifluoromethyl (-CF3)-tagged agent.

Main Results:

• The agent exhibits no 19F MR signal in its Fe(III) state due to paramagnetic relaxation.
• Upon reduction to the Fe(II) state by cysteine, a robust 19F signal is observed.
• The agent's response to redox changes is reversible, confirmed by successive oxidation and reduction cycles.
• Simultaneous 19F MRI monitoring of the -SF5 agent and a -CF3 agent demonstrated multicolor imaging capability.

Conclusions:

• A novel, responsive, and reversible 19F MRI agent with a -SF5 tag has been developed.
• The agent effectively detects reducing environments, showing potential for monitoring biological processes.
• The -SF5 tag facilitates multicolor imaging, enabling simultaneous detection of multiple targets or conditions.