Application of astatine-210: Evaluation of astatine distribution and effect of pre-injected iodide in whole body of normal rats.

We proposed use of astatine-210 in preclinical study. Astatine-210 has higher yield of production and is easier to quantify than astatine-211. We produced astatine-210 with Bi target and 40 MeV alpha beam accelerated by cyclotron, free astatine-210 was separated and injected to normal rats. Three male rats (blocking group) were injected non-radioactive iodide before injection of astatine-210. Compared with the control group, the astatine-210 accumulations in the blocking group decreased to 24% in the thyroid.

Observation of the chemical reaction equilibria of element 104, rutherfordium: solid-liquid extraction of Rf, Zr, Hf and Th with Aliquat 336 resin from HCl.

We successfully observed the equilibrium state of the chemical reactions for superheavy elements on a one-atom-at-a-time scale; we investigated the time dependence of the extraction behaviour of element 104, Rf. The distribution coefficient of Rf in 9 M HCl was found to be higher than those of its homologous elements, probably due to differences in the chloride complexation of Rf.

Preparation and evaluation of an astatine-211-labeled sigma receptor ligand for alpha radionuclide therapy.

INTRODUCTION: Sigma receptors are overexpressed in a variety of human tumors, making them potential targets for radionuclide receptor therapy. We have previously synthesized and evaluated (131)I-labeled (+)-2-[4-(4-iodophenyl)piperidino]cyclohexanol [(+)-[(131)I]pIV], which has a high affinity for sigma receptors. Therefore, (+)-[(131)I]pIV significantly inhibited tumor cell proliferation in tumor-bearing mice. In the present study, we report the synthesis and the in vitro and in vivo characterization of (+)-[(211)At]pAtV, an (211)At-labeled sigma receptor ligand, that has potential use in alpha-radionuclide receptor therapy. METHODS: The radiolabeled sigma receptor ligand (+)-[(211)At]pAtV was prepared using a standard halogenation reaction generating a 91% radiochemical yield with 98% purity after HPLC purification. The partition coefficient of (+)-[(211)At]pAtV was measured. Cellular uptake experiments and in vivo biodistribution experiments were performed using a mixed solution of (+)-[(211)At]pAtV and (+)-[(125)I]pIV; the human prostate cancer cell line DU-145, which expresses high levels of the sigma receptors, and DU-145 tumor-bearing mice. RESULTS: The lipophilicity of (+)-[(211)At]pAtV was similar to that of (+)-[(125)I]pIV. DU-145 cellular uptake and the biodistribution patterns in DU-145 tumor-bearing mice at 1h post-injection were also similar between (+)-[(211)At]pAtV and (+)-[(125)I]pIV. Namely, (+)-[(211)At]pAtV demonstrated high uptake and retention in tumor via binding to sigma receptors. CONCLUSION: These results indicate that (+)-[(211)At]pAtV could function as an new agent for alpha-radionuclide receptor therapy.

Feasibility studies towards future self-sufficient supply of the (99)Mo-(99m)Tc isotopes with Japanese accelerators.

In order to establish a self-sufficient supply of (99m)Tc, we studied feasibilities to produce its parent nucleus, (99)Mo, using Japanese accelerators. The daughter nucleus, (99m)Tc, is indispensable for medical diagnosis. (99)Mo has so far been imported from abroad, which is separated from fission products generated in nuclear reactors using enriched (235)U fuel. We investigated (99m)Tc production possibilities based on the following three scenarios: (1) (99)Mo production by the (n, 2n) reaction by spallation neutrons at the J-PARC injector, LINAC; (2) (99)Mo production by the (p, pn) reaction at Ep = 50-80 MeV proton at the RCNP cyclotron; (3) (99m)Tc direct production with a 20 MeV proton beam from the PET cyclotron. Among these three scenarios, scenario (1) is for a scheme on a global scale, scenario (2) works in a local area, and both cases take a long time for negotiations. Scenario (3) is attractive because we can use nearly 50 PET cyclotrons in Japan for (99m)Tc production. We here consider both the advantages and disadvantages among the three scenarios by taking account of the Japanese accelerator situation.

Selective accumulation of [6²Zn]-labeled glycoconjugated porphyrins as multi-functional positron emission tomography tracers in cancer cells.

Positron-emission tomography (PET) can be used to visualize active stage cancer. Fluorine-18 ([(18)F])-labeled 2-([(18)F])2-deoxy-2-fluoroglucose (([(18)F])-FDG), which accumulates in glucose-dependent tissues, is a good cancer-targeting tracer. However, ([(18)F])-FDG is obscured in glucose-dependent normal tissues. In this study, we assessed the cancer-selective accumulation of zinc-labeled glycoconjugated 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (ZnGlc1-4), both in vitro and in vivo. Experiments using both normal and cancer cells confirmed the relationship between cancer cell-selective accumulation and the substitution numbers and orientations of glycoconjugated porphyrins. ZnGlctrans-2 accumulated at greater levels in cancer cells compared with other glycoconjugated porphyrins. PET imaging showed that ZnGlctrans-2 accumulated in tumor.

Development of an online preparation system for multitracer solutions.

We have developed a new target-irradiation system for the online preparation of multitracer solutions, where the nuclear-reaction products recoiling out of the target are directly implanted in a solvent as a liquid catcher. A rapid online transportation of the solution has enabled highly efficient recovery of the multitracer solutions having even short-lived radioactive isotopes without any chemical treatments. It has been suggested that the collection efficiency depends on the chemical properties of the recoil elements.