Core-multi-shell design: unlocking multimodal capabilities in lanthanide-based nanoparticles as upconverting,...

Area of Science:

• Nanotechnology and Materials Science
• Biomedical Imaging
• Radiochemistry

Background:

• Multimodal bioimaging probes integrating optical, MRI, and CT offer significant biomedical potential.
• Lanthanide-based nanoparticles are attractive due to their inherent optical, magnetic, and X-ray attenuation properties.
• Dy³⁺ doping in upconversion nanoparticles (UCNPs) for MRI can lead to luminescence quenching via energy transfer.

Purpose of the Study:

• To develop and characterize lanthanide-based core/shell/shell nanoparticles (Dy-CSS NPs) for multimodal optical/MRI/CT bioimaging.
• To investigate the effect of inner NaGdF₄ shell thickness on mitigating Dy³⁺-induced upconversion luminescence quenching.
• To evaluate the MRI T₂ relaxivity and CT contrast performance of the engineered Dy-CSS NPs.

Main Methods:

• Synthesis of hexagonal-phase (β)-NaGdF₄:Yb,Er/NaGdF₄/NaDyF₄ core/shell/shell nanoparticles (Dy-CSS NPs).
• Characterization of nanoparticle architecture and optical properties, including upconversion (UC) emission spectra and Yb³⁺ excited state lifetimes.
• In vitro MRI T₂ relaxivity measurements at 7 T and in vitro CT imaging phantom studies at 110 keV.

Main Results:

• A 4 nm NaGdF₄ inner shell effectively restored and enhanced the upconversion emission, overcoming Dy³⁺ poisoning.
• The thickest outer NaDyF₄ shell (4 nm) yielded the highest T₂ relaxivity (r₂), outperforming commercial agents.
• Dy-CSS NPs demonstrated suitable performance for CT imaging, comparable to iodine-based contrast agents.

Conclusions:

• Optimized Dy-CSS NP architecture with a precisely tuned inner shell thickness can overcome luminescence quenching issues.
• These engineered nanoparticles exhibit superior MRI T₂ contrast and viable CT imaging capabilities.
• The developed Dy-CSS NPs represent promising multimodal agents for advanced bioimaging applications.