Abstract ▼

Ⅳ. Result
1. Target development for ⁶⁸Ge production and the production and the separation of ⁶⁸Ge
^natGa(p,xn)⁶⁸Ge was selected as a nuclear reaction for the production of ⁶⁸Ge.Based on the result of SRIM code simulation, proton energy was

Ⅳ. Result
1. Target development for ⁶⁸Ge production and the production and the separation of ⁶⁸Ge
^natGa(p,xn)⁶⁸Ge was selected as a nuclear reaction for the production of ⁶⁸Ge.Based on the result of SRIM code simulation, proton energy was determined as 29 MeV at the first stage of research. Target for the test production was designed and fabricated according to this energy, and then, ⁶⁸Ge was produced by using MC-50 cyclotron of KIRAMS and RFT-30 cyclotron of ARTI. According to the analysis result of test production, proton energy was changed to 26 ~ 27 MeV for the integrity of target. In addition, exclusive target irradiation station, transport system, and target treatment device were developed for the capsuled target. The property evaluation of various metals was also performed for the application to Ga encapsulation. Ti, Nb, and Mo foils were heated in the liquid Ga environment for 2 weeks. According to the result of scanning electron microscopy, a Nb foil showed the least amount of Ga adhesion while a Ti foil exhibited the most amount of Ga adhesion. Results of energy dispersive X-ray spectroscopy and X-ray diffraction analysis displayed that Ga just physically adhered to metal foils without any chemical bonding. Finally, result of X-ray photoelectron spectroscopy revealed that Nb was oxidized by heating in the liquid Ga while Mo was rather partially reduced. Both Nb and Mo can be candidates for the Ga encapsulation, but it is considered that Mo is better for the development of high-energy target for ⁶⁸Ge production.

2. Separation and purification of ⁶⁸Ge
Using stable isotopes (⁷²Ge, ⁶⁹Ga), condtion of ⁶⁸Ge production was indirectly realized. As a result of back extraction method using acid solution, erupted solution was composed of Ge higher than 90% and Ga lower than 0.1%. It means that Ge was successfully separated. Based on this result, ⁶⁸Ge separation process was performed. Proton-irradiated target was put in beaker, and then, heated. After irradiated solid target (^natGa + ⁶⁸Ge) was liquified, ⁶⁸Ge was extracted by using 5 ml of 4 N HCl and 2 ml of 30% H₂O₂. 510 keV peak, corresponding to the annhilation energy of β+ produced for the decay of ⁶⁸Ge, was observed.

3. Development of adsorbent for ⁶⁸Ge/⁶⁸Ga generator
In column adsorbent of ⁶⁸Ge/⁶⁸Ga generator, a long-lived parent radionuclide(t_1/2=271 d) and its short-lived daughter radionuclide (t_1/2=68min) make radiative equilibrium. In order to find much more suitable generator adsorbents, we carried out various adsorbents experiment. The ability of the adsorbent to adsorb various metal oxides, mineral and metal phosphate was investigated in order to evaluate the possibility of its use in germanium adsorption and gallium desorption. The adsorbents were fully characterized by spectroscopic analysis equipments. The plastic syringe (volume: 1.8 ㎖, height: 56 mm) chromatographic column fitted with polyethylene frit (polyethylene, pore: 20μm) at the bottom was packed with 200 mg of adsorbents. Germanium-68 solution (6 μCi/㎕) containing germanium and gallium impurities were passed through the metal oxide column at a flow rate of 1 ㎖/min and the effluent was collected. All radioactivity was measured by dosimeter. The selective TiO₂, CeO₂, Al/W/Ti and Zr(HPO₄)₂ based ⁶⁸Ge/⁶⁸Ga generator has been composed and evaluation. High purity of ⁶⁸Ga elution was obtained with in 1 minute as a 1.0 ㎖ volume of 0.1N and 0.4 N HCl fractions. We were successfully achieved a high radio chemical purity and low breakthrough of ⁶⁸Ge using the various adsorbents as the column material. These ⁶⁸Ga/⁶⁸Ga generator adsorbents have high potential for use in sources of PET radioisotopes.

4. Development of shield case for ⁶⁸Ge/⁶⁸Ga generator
For the shielding the ⁶⁸Ge/⁶⁸Ga generator, Pb and W were chosen and the generator was designed and fabricated. According to the results of MCNP analysis, 25mm(Pb) and 15mm(W) are enough for the legal transport regulation. In this research, shield case for the generator was design and manufactured with 40mm(Pb) and 30mm(W) conservatively.

5. Development of ⁶⁸Ga labelled radiopharmaceuticals
⁶⁸Ga-SCN-DOTA/NOTA-PCA (⁶⁸Ga labelled benzamide derivative) was synthesized with a radiochemical yield of ~80% and a radiochemical purity of >97% by analytical HPLC. It showed stability with higher thatn 95% during the in vitro stability test of 2 h. The in vitro binding of ⁶⁸Ga-benzamide derivatives to melanin and its cellular uptake demonstrated the selective uptake in melanin. In addition, the biodistribution and micro–PET imaging of benzamide derivatives in B16F10 tumor models showed the specific accumulation in melanoma. These results suggest that⁶⁸Ga-SCN-DOTA-PCA would be a promising agent for melanoma diagnosis.

[ ⁶⁸Ga ]nanocomposites were synthesized using Ga-68 after preparing nanocoreshell with DOTA-PAMAM dendrimer complex and NOTA-ctiric acid on the surface of Fe₃O₄ nanoparticles (NPs). The fabricated nanocomposites were characterized by NMR, XRD, MS, TEM, Zeta sizer etc. Radio-TLC and HPLC confirmed the formation of ⁶⁸Ga-DOTA/NOTA complex. The size of as synthesized nanocomposites was 11.5 nm and after surface modification progresses, the size of NPs was gradually increased to 15.3 nm. The nanocomposites with stable gallium isotope showed excellent biocompatibility and [ ⁶⁸Ga ]nanocomposites have high uptake on CT-26, SKBR-3, KB and A 549 cell line. The values of cellular uptake was attained a maximum of 9.764 % at 60 min for CT-26, 13.591 % at 120 min for SK-BR-3 cell line, 9.6133 % at 60 min for KB and 10.861 % at 120 min for A549. These detailed studies established that ⁶⁸GaNHFCNP exhibits potential application for cancer contrast.