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

Liu, Ning; Ding, Hongliu; Vanderheyden, Jean-Luc; Zhu, Zhihong; Zhang, Yumin

doi:10.1016/j.nucmedbio.2007.02.006

« Previous Next »Nuclear Medicine and Biology
Volume 34, Issue 4 , Pages 399-404, May 2007

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

Ning Liu
- Department of Radiology/Nuclear Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA
- Current address: Millennium Pharmaceuticals, Inc., Cambridge, MA, USA.
Hongliu Ding
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01655, USA
Jean-Luc Vanderheyden
- Department of Radiology/Nuclear Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA
- Current address: GE Healthcare, Waukesha, WI, USA.
Zhihong Zhu
- Department of Radiology/Nuclear Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA
- Current address: Siemens Biomarker Solutions, North Wales, PA, USA.
Yumin Zhang
- Department of Radiology/Nuclear Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA
- Corresponding author. Department of Experimental Imaging, Integrative Pharmacology–Advanced Technology, Abbott Laboratories, Abbott Park, IL 60064, USA. Tel.: +1 847 937 8523; fax: +1 847 938 0072.

Received 23 January 2007; received in revised form 1 February 2007; accepted 15 February 2007.

Abstract

To develop a noninvasive direct method for the in vivo tracking of small interfering RNA (siRNA) used in RNA interference, two 18-nucleotide oligoribonucleotides were radiolabeled with technetium-99m (^99mTc-RNA). The ability of ^99mTc-RNA to track delivery was tested in cultured cells and living mice. The cellular delivery of ^99mTc-RNAs could be quantified by gamma counting and could be visualized by microautoradiography. Radiolabeled RNAs can be efficiently delivered into cells by reaching up to 3×10⁵ molecules of small RNAs per cell. Moreover, RNAs were internalized with homogeneous distribution throughout the cytoplasm and nucleus. In tumor-bearing mice, whole-body images and biodistribution studies showed that ^99mTc-RNAs were delivered to almost all tissues after intravenous injection. The imaging of living animals allowed noninvasive and longitudinal monitoring of the in vivo delivery of these small RNAs. In conclusion, using ^99mTc radiolabeling, the delivery of small RNAs could be measured quantitatively in cultured cells and could be noninvasively visualized in living animals using a gamma camera. The results of this study could open up a new approach for measuring the in vivo delivery of small RNAs that might further facilitate the development of siRNAs as targeted therapies.

Keywords: Small RNA, ^99mTc radiolabeling, Cell culture, Mouse, Biodistribution