Radiolabeling of DNA Bipyramid and Preliminary Biological Evaluation in Mice

Self-assembled DNA nanostructures, as a new type of nanocarriers, have shown great potential in molecular imaging probes. DNA bipyramid nanostructures (DBNs), as a classic kind of DNA nanostructure, can be precisely constructed through the unparalleled base-pairing precision of oligonucleotide strands. DBNs were prepared by self-assembly of six oligonucleotides with equal molar amounts in a single annealing step, and purified by high performance liquid chromatography (HPLC). DBNs were stable in 10% FBS as well as 80% mouse serum for at least 8 h. To prepare Tc-99m-labeled DBNs, N-hydroxysuccinimidyl S-acetylmercaptoacetyl triglycinate (Sacetyl-MAG3-NHS ester) tagged single-stranded DNA (ssDNA) was first radiolabeled with Tc-99m, and DBNs with an overhang were assembled and then hybridized with Tc-99m-ssDNA to prepare Tc-99m-labeled DNA bipyramid nanostructures (Tc-99m-MAG3-DBNs). DBNs were radiolabeled, with the radiochemical purity being over 90%. The plasma half-life of Tc-99m-MAG3-DBNs in normal KM mice was about 6 min. The biodistribution and SPECT/CT imaging were conducted with Tc-99m-MAG3-DBNs in KM mice, and both showed that Tc-99m-MAG3-DBNs mainly concentrated in the intestine, liver, and kidneys, and there was also prominent uptake in the gallbladder and bladder. We successfully obtained a new class of SPECT molecular probes based on this DNA polyhedron structure.