Preparation and preliminary evaluation of ^99mTc-labeled Tetrahedral DNA Nanoparticles

Objectives DNA nanostructures are an emerging variety of DNA-based nanoscale complexes, which possesses extraordinary biodegradable properties for in vivo applications. The purpose of this study is to evaluate biological properties of a Technitium-99m labeled tetrahedral DNA nanoparticles (TDNs) in vitro and in vivo.

Methods TDNs (~6 nm) were constructed via a rapid annealing step of four oligonucleotides, and side arms were designed on the edges of TDNs for hybridization of ^99mTc-labeled single-stranded DNA (^99mTc-ssDNA). Radio-TLC was used to monitor the radiolabeling results. After characterization and purification processes, the biodistribution of ^99mTc-TDNs in normal mice was analyzed, and SPECT/CT imaging were performed.

Results TDNs could be successfully prepared and characterized by atomic force microscope (AFM) and dynamic light scattering (DLS) analysis, showing that TDNs with theoretical diameters of 7 nm, actually have a hydrodynamic diameter of about 13 nm. Labeling efficiency of TDNs was about 90% based on radio thin-layer chromatography (Radio-TLC), and radiochemistry purity of ^99mTc-TDNs was about 95% based on radio-HPLC. After intravenous injection of ^99mTc-TDNs, the plasma half-life of ^99mTc-TDNs in vivo was measured to be about 5.5 min. Biodistribution analysis showed that ^99mTc-TDNs had a high uptake in the bladder and the liver.

Conclusions We have successfully prepared tetrahedral DNA nanostructures and radiolabeled the structure with high efficiency for in vivo biological evaluation. The half-life of TDNs in mice was about 5.5 min, and biodistribution analysis suggested that ^99mTc-TDNs mainly metabolized by the liver and would rapidly excrete to the bladder through kidneys. The great biocompatibility and biodegradability of TDNs entitled themselves a promising future within the areas of biomedical study.

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