Radiolabeling small RNA with technetium-99m for visualizing cellular delivery and mouse biodistribution

Area of Science:

• Biotechnology
• Molecular Biology
• Radiochemistry

Background:

• RNA interference (RNAi) therapies utilize small interfering RNA (siRNA) for gene silencing.
• Effective delivery and tracking of siRNA in vivo are crucial for therapeutic development.
• Current methods for tracking siRNA delivery can be invasive or lack real-time monitoring.

Purpose of the Study:

• To develop a noninvasive direct method for in vivo tracking of siRNA.
• To quantify and visualize the cellular and in vivo delivery of radiolabeled siRNA.
• To assess the potential of technetium-99m radiolabeling for monitoring siRNA distribution.

Main Methods:

• Radiolabeling of two 18-nucleotide oligoribonucleotides with technetium-99m ((99m)Tc-RNA).
• Testing delivery in cultured cells using gamma counting and microautoradiography.
• In vivo imaging and biodistribution studies in tumor-bearing mice after intravenous injection.

Main Results:

• Efficient cellular delivery of (99m)Tc-RNAs (up to 3x10(5) molecules/cell) with homogeneous cytoplasmic and nuclear distribution.
• Intravenous injection led to delivery of (99m)Tc-RNAs to most tissues in tumor-bearing mice.
• Noninvasive imaging allowed longitudinal monitoring of in vivo small RNA delivery.

Conclusions:

• Technetium-99m radiolabeling provides a quantitative method for measuring small RNA delivery in cells.
• Noninvasive visualization of small RNA delivery in living animals is achievable using a gamma camera.
• This approach may facilitate the development of siRNA-based targeted therapies by improving delivery monitoring.