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Technetium-99m labeling of DNA oligonucleotides
D J Hnatowich1, P Winnard, F Virzi
1Department of Nuclear Medicine, University of Massachusetts Medical Center, Worcester 01655, USA.
Summary
Stable radiolabeling of single-stranded DNA with technetium-99m (99mTc) was achieved using the hydrazino nicotinamide (SHNH) moiety. This method preserves DNA function for potential in vivo radiopharmaceutical applications.
Area of Science:
- Bioconjugation Chemistry
- Radiopharmaceutical Development
- Molecular Biology
Background:
- Single-stranded DNA and RNA oligonucleotides show promise as radiopharmaceuticals for in vivo applications.
- Development of convenient and stable methods for radionuclide attachment, such as technetium-99m (99mTc), is crucial for their utility.
Purpose of the Study:
- To develop and evaluate a method for stably radiolabeling amino-modified single-stranded DNA with 99mTc.
- To compare the stability and functionality of 99mTc-labeled DNA with DNA labeled using a different radionuclide (111In) and chelator.
Main Methods:
- Amino-modified single-stranded DNA oligonucleotides were conjugated with either the hydrazino nicotinamide (SHNH) moiety or diethylenetriaminepentacetic acid (DTPA).
- DNA was radiolabeled with 99mTc via transchelation from glucoheptonate (using SHNH) or with 111In acetate (using DTPA).
- Labeling efficiency, DNA hybridization ability, serum protein binding, and stability in serum were assessed using High-Performance Liquid Chromatography (HPLC) and streptavidin-conjugated magnetic beads.
Main Results:
- High conjugation efficiency was achieved for both SHNH-DNA and DTPA-DNA.
- Radiolabeling efficiencies were up to 60% for 99mTc-SHNH-DNA and up to 100% for 111In-DTPA-DNA.
- Both radiolabeled DNAs retained their ability to bind to streptavidin and hybridize with complementary DNA.
- 99mTc-labeled DNA showed significant serum protein binding, while 111In-labeled DNA exhibited degradation products.
- Stability in human serum over 24 hours was better for 99mTc-SHNH-DNA (less than 4% loss) compared to 111In-DTPA-DNA (14% loss).
Conclusions:
- Amino-modified single-stranded DNA can be stably radiolabeled with 99mTc using the SHNH moiety.
- This method allows for radiolabeling without compromising the DNA's biological function.
- The developed 99mTc labeling method offers a promising approach for developing DNA-based radiopharmaceuticals.