Slowing Down Water: Enhanced and Cation-responsive MRI Contrast.

Area of Science:

• Nanoparticle science
• Magnetic Resonance Imaging (MRI)
• Supramolecular chemistry

Background:

• Paramagnetic centers confined within mesoporous nanoparticles offer unique properties.
• Outer sphere effects and water diffusion are influenced by nanoparticle channel confinement.
• Mesoporous nanoparticle side wall modifications allow for tuning of local water environments.

Purpose of the Study:

• To investigate the impact of kosmotropic effects on water viscosity around internalised paramagnetic complexes.
• To enhance MRI contrast (T1 and q=0) using tailored mesoporous nanoparticles.
• To develop physiologically relevant, potassium-responsive MRI.

Main Methods:

• Utilizing mesoporous nanoparticles with internalised paramagnetic centers.
• Modifying nanoparticle side walls to induce kosmotropic (water-ordering) effects.
• Employing crown ethers for cation binding and subsequent water organization modulation.

Main Results:

• Demonstrated significant increase in water viscosity near paramagnetic complexes.
• Achieved unprecedented image contrast for q=0 systems and enhanced T1 contrast for q=1 complexes at clinical field strengths.
• Enabled potassium-responsive MRI by modulating water organization through crown ether-cation interactions.

Conclusions:

• Mesoporous nanoparticle confinement and side wall engineering are effective strategies for enhancing MRI contrast.
• Kosmotropic effects and controlled water organization are key to improving MRI performance.
• The developed system shows promise for advanced diagnostic imaging, including physiologically relevant potassium sensing.