In Vivo MRI of Functionalized Iron Oxide Nanoparticles for Brain Inflammation

Area of Science:

• Neuroscience
• Immunology
• Biomedical Imaging

Background:

• Microglia are crucial brain immune cells, with activation implicated in numerous central nervous system disorders.
• Current imaging probes for activated microglia lack specificity, often targeting proteins present on multiple cell types.
• Noninvasive imaging of activated microglia is essential for both research and clinical applications.

Purpose of the Study:

• To develop a novel multimodal imaging probe for selective visualization of activated microglia.
• To target the scavenger receptor class A (SR-A) expressed on activated microglia.
• To evaluate the efficacy and safety of the developed imaging probe in a preclinical model.

Main Methods:

• Design and synthesis of sulfated dextran-coated iron oxide (SDIO) nanoparticles as a PET/MRI multimodal imaging probe.
• Selective targeting of scavenger receptor class A (SR-A) on activated microglia.
• Intravenous administration of SDIO in a mouse model with induced microglial activation (TNF-α).
• Visualization of activated microglia using T2-weighted MRI.

Main Results:

• SDIO nanoparticles were readily taken up by activated microglia and demonstrated low toxicity in vivo.
• Intravenous SDIO administration enabled clear visualization of activated microglia via T2-weighted MRI.
• Significant contrast enhancement was observed in SDIO-treated animals compared to controls, confirming probe specificity.
• Non-targeted nanoparticles did not yield significant contrast changes.

Conclusions:

• SR-A targeting represents a highly promising strategy for the specific, noninvasive imaging of activated microglia in the brain.
• The developed SDIO nanoparticles offer a potential tool for advancing research and clinical applications in neuroinflammatory diseases.
• This multimodal imaging approach enhances the specificity of activated microglia detection, overcoming limitations of current PET probes.