In vivo MRI of hyperpolarized silicon-29 nanoparticles.

Area of Science:

• Nanotechnology
• Biomedical Imaging
• Materials Science

Background:

• Hyperpolarized nanoparticles offer enhanced sensitivity for magnetic resonance imaging (MRI).
• Previous studies focused on larger, micrometer-sized particles, limiting potential applications.
• Investigating smaller nanoparticles is crucial for exploring novel imaging contrast agents.

Purpose of the Study:

• To assess the feasibility of in vivo imaging using hyperpolarized 50-nm silicon-29 (²⁹Si) nanoparticles.
• To compare the performance of small nanoparticles with larger ones in preclinical models.
• To evaluate the biodistribution and clearance of these nanoparticles in vivo.

Main Methods:

• Hyperpolarization of 50-nm ²⁹Si nanoparticles using dynamic polarization transfer.
• Phantom experiments to analyze relaxation times (T1 and T2) and effects of surface coatings.
• In vivo imaging in mice following various administration routes (intraperitoneal, intragastric, intratumoral) and tissue clearance analysis via ICP-OES.

Main Results:

• Successful in vivo imaging of hyperpolarized 50-nm ²⁹Si nanoparticles was achieved across different administration routes.
• Small nanoparticles exhibited improved distribution compared to micrometer-sized particles after intraperitoneal and intragastric injection.
• Ex vivo analysis confirmed sufficient clearance of nanoparticles within 14 days post-injection.

Conclusions:

• In vivo MRI using hyperpolarized 50-nm ²⁹Si nanoparticles is feasible.
• These small nanoparticles demonstrate comparable polarization levels and relaxation times to larger particles.
• The findings support the potential of small ²⁹Si nanoparticles as advanced contrast agents for biomedical imaging.