Development of a double-stranded siRNA labelling method by using ^99mTc and single photon emission computed tomography...

Area of Science:

• Molecular Biology
• Biomedical Imaging
• Radiochemistry

Background:

• In vivo biodistribution of small interfering RNAs (siRNAs) is crucial for developing RNA interference (RNAi) therapies.
• Accurate tracking of siRNA delivery and target engagement is essential for therapeutic efficacy.

Purpose of the Study:

• To develop a novel method for real-time in vivo biodistribution analysis of siRNA using single photon emission computed tomography (SPECT).
• To assess the utility of 99mTc-radiolabeled siRNA targeting lacZ for visualizing lacZ gene expression in vivo.

Main Methods:

• siRNA targeting lacZ was radiolabeled with 99mTc using the bifunctional chelator diethylenetriamine-N,N,N',N″,N″-pentaacetic acid (DTPA).
• Labeling efficiency, specific activity, and probe stability in RNaseA were determined.
• SPECT imaging was performed in mice overexpressing the lacZ gene in the liver.

Main Results:

• The 99mTc-labeled siRNA remained highly stable in RNaseA solution at 37°C.
• SPECT imaging revealed significant 99mTc accumulation in the liver of mice overexpressing the lacZ gene.
• The 99mTc-labeled lacZ siRNA demonstrated beta-galactosidase-specific accumulation.

Conclusions:

• 99mTc-labeled lacZ siRNA is a promising tool for visualizing lacZ expression in vivo.
• The developed radiolabeled siRNA enables targeted delivery and visualization in regions overexpressing the target gene.
• This approach facilitates real-time assessment of siRNA biodistribution and therapeutic potential.