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Introduction Nitroimidazole (azomycin) derivatives labeled with radioisotopes have been developed as cancer imaging and radiotherapeutic agents based on the oncological hypoxic mechanism. By attaching nitroimidazole core with different functional groups, we synthesized new nitroimidazole derivatives, and evaluated their potentiality as tumor imaging agents. Methods Starting with commercially available 2-nitroimdazole, 2-fluoro-N-(2-(2-nitro-1H-imidazol-1-yl)ethyl)acetamide (NEFA, [19F]7) and 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl 2-fluoroacetate (NEFT, [19F]8), as well as radiolabeling precursors - the bromo substituted analogs were quickly synthesized through a three-step synthetic pathway. The precursors were radiolabeled with [18F]F-/18-crown-6/KHCO3 in DMSO at 90 °C for 10 min followed by purification with an Oasis HLB cartridge. Biodistribution studies were carried out in EMT-6 tumor-bearing mice. The uptake (%ID/g) in tumors and normal tissues were measured at 30 min post injection. Liquid chromatography-electrospray ionization mass spectrometry (LC/MS) was used to distinguish metabolites from parent drugs in urine and plasma of rat injected with “cold” NEFA ([19F]7) and NEFT ([19F]8). Results Two radiotracers, [18F]NEFA ([18F]7) and [18F]NEFT ([18F]8), were prepared with average yields of 6-7% and 9-10% (no decay corrected). Radiochemical purity for both tracers was >95% as determined by HPLC. Biodistribution studies in EMT-6 tumor-bearing mice indicated that the tumor to blood and tumor to liver ratios of both [18F]7 (0.96, 0.98) and [18F]8 (0.61,1.10) at 30 min were higher than those observed for [18F]FMISO (1) (0.91, 0.59), a well-investigated azomycin type hypoxia radiotacer. LC/MS analysis demonstrated that fluoroacetate was the main in vivo metabolite for both NEFA ([19F]7) and NEFT ([19F]8). Conclusions In this research, two new fluorine-18 labeled 2-nitroimdazole derivatives, [18F]7 and [18F]8, both of which containing in vivo hydrolyzable group, were successfully prepared. Further biological evaluations are warranted to investigate their potential as PET radioligands for imaging tumor.

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Abstract. In recent years, measurement of surface soil moisture by the cosmic-ray fast neutron probe has gradually attracted more attention The intensity of the fast neutrons above the ground is sensitive to water content changes, largely insensitive to soil chemistry and inversely correlated with hydrogen content of the soil. Measurement of this intensity with a portable neutron detector placed above the ground permits the possibility of monitoring soil moisture. By this passive, non-invasive and intermediate scale measurement, soil moisture at a horizontal scale of around 660 m and depths of 12 to 76 cm can be inferred. And the large footprint makes this method suitable for weather and short-term climate forecast initialization and for validation of soil moisture inversed from satellite sensors. In this paper, the results of the cosmic-ray instruments well reflected the variation trend of soil moisture at the field scale. We found that irrigation and infiltration were two most important factors that affected the variation of soil moisture during a growing season of maize in Zhangye and the soil moisture of different period in the growing season of maize was very different. At last, Wireless Sensor Network data were used to validate this result and we found their correlation was very well with a RMSE of 0.0275 m 3 m -3 in the non-irrigation time.