Abstract: The radio-isotope labelled biomolecules (i.e., peptide, protein) have been widely used as in-vivo imaging probe, but suffer from fast excretion, off-target effect, and lack of biological stability. It has been known that the use of nanoparticle can alter the pharmacokinetics and pharmacodynamics of conventional drug molecules. In this regards, nano-sized imaging probe with high sensitivity and excellent biological stability was greatly demanded.
Here, we report highly sensitive and stable SPECT imaging probe by use of simple chemistry of sodium iodide (125) and adenine-rich oligonucleotide modified AuNP, and seed-mediated Au shell growth in solution. In theory, two thousands of Iodine-125 can be covalently conjugated to DNA base per gold nanoparticle (20 nm), which can greatly increase the radio sensitivity of nanoparticle. Iodine-125 embedded Au@Au nanostructure was synthesized by forming uniform Au shell with 10 nm thickness, which can improve the stability of Iodine-125 label on gold nanoparticle by preventing possible hydrolysis or enzymatic attacks in in-vivo. Three different diameter of Iodine-125 embedded Au@Au nanostructure (27, 32, 42 nm) were prepared to investigate radio sensitivity, biological stability, and in-vivo distributions for efficient SPECT imaging. A series of analysis showed highly sensitive radio activity, increased stability of Au@Au nanostructure, and size-dependent particle distributions in normal mice.