Speciation and estimation of radioiodine in reactor coolant water

The species of radioiodine in the primary coolant water of the heavy water moderated, heavy water cooled 100 MW research reactor have been identified. It was observed that IO ₃ ^? was the major species in the reactor coolant during reactor operation and I^? was the major species during shutdown. Organic and elemental forms amount only to less than 2% of total radioiodine. A simple method was developed for the estimation of gross iodine activity in reactor coolant water. The method involves the separation of all inorganic forms of iodine into a photographic film consisting of a thin layer of silver halide. The iodine in the film was estimated by gross counting of the film in a Geiger-Müller counter. Gross iodine activity in the reactor coolant samples estimated by the present method were in agreement with that obtained by direct γ-spectrometry with a Ge detector. It is concluded that the method can be used for the routine estimation of radioiodine in reactor coolant water.¹³³I/¹³¹I and¹³⁵I/¹³¹I ratios in the film were estimated and found to be useful in identifying split rod conditions in the reactor.     

Simple preparation of76Br,123I and211At labeled 5-halo-2′-deoxyuridine

A fast and easy method for the preparation of radiolabeled 5-halo-2-deoxyuridine (halo=[⁷⁶Br], [¹²³I] and [²¹¹At]) is presented. Labeling is accomplished by oxidation of the halogenide with Iodogen for [¹²³I] and [²¹¹At], and Chloramine-T (CAT) for [⁷⁶Br] followed by halodestannylation of 5-trimethylstannyl-2-deoxyuridine (TMSUdR). The reaction takes 1 minute giving >90% yield for all three halogens.     

Radioiodination of insulin using N-succinimidyl 5-(tributylstannyl)-3-pyridine-carboxylate (SPC) as a bi-functional linker: Synthesis and biodistribution in mice</p> </p>

Summary Insulin receptors are overexpressed on a number of human tumors, leading to significant affinity of insulin to these tumors. It is appealing to receptor-targeted radiotherapy for malignant tumors if insulin is labeled with suitable radionuclide. In this paper, N-succinimidyl 5-(tributylstannyl)-3-pyridinecarboxylate (SPC), a potential bi-functional linker for radioiodination of proteins or peptides, was synthesizedby using 5-bromonicotinic acid as the starting material. Then, with this bi-functional linker, insulin was conjugated with ¹³¹I, and the tissue distribution of the labeled insulin (¹³¹I-SIPC-insulin) in normal mice was investigated. The results showed that insulin ^</span> could be conjugated with¹³¹I using SPC as the linker ^</span> in a labeling yield of40-58%, and with radiochemical purity of more than 98% after purification bySephadex?G-10. Even kept at room temperature for 72 hours, the radiochemical purity of ¹³¹I-SIPC-insulin was still more than 97%, implying that the conjugated insulin was constantly stable in vitro.Meanwhile, in order to evaluate the in vivo stability of the conjugated compounds, insulin was also labeled with ¹³¹I by a direct method using chloramine-T (Ch-T) as the electrophilic agents.Biodistribution of¹³¹I-SIPC-insulinin micesuggested that ¹³¹I could clear rapidly from the blood,mainly excreted by kidney. However, ¹³¹I uptake of mice with¹³¹I-SIPC-insulin in some key organs, especially in thyroid and stomach, were much less (150 or 30 times) than that with the direct labeled insulin (¹³¹I-insulin). Additionally, it was noted that ¹³¹I-SIPC-insulin hasmuch betterinvivo stability than¹³¹I-insulin.</p> </p>     

Preparation of 125I-Lanreotide and its biodistribution in murine model of melanoma

Lanreotide, a somatostatin analogue, was radioiodinated with ¹²⁵I to explore the possibility of using ¹²³I labeled lanreotide as a diagnostic radiopharmaceutical for tumors overexpressing somatostatin (SST) receptors. Radioiodination was carried out with ¹²⁵I using chloramine T as the oxidant. The labeling yield was >90%. Characterization of ¹²⁵I-Lanreotide was carried out by paper electrophoresis as well as HPLC. ¹²⁵I-Lanreotide was purified by chromatography using a C18 Sep-Pak column. Radiochemical purity of the purified ¹²⁵I-Lanreotide thus obtained was >99%. Significant tumor uptake of ¹²⁵I-Lanreotide was observed in C57BL/6 mice bearing melanoma.     

Separation of iodine produced from fission with a porous metal silver column in99Mo production

In Argentina, at the Ezeiza Atomic Center,¹³¹I is produced by wet distillation of natural tellurium dioxide irradiated with thermal neutrons in a pool-type reactor. In order to recover the¹³¹I present in the production process of fission⁹⁹Mo obtained by irradiation of UAL_x/Al targets (with 90% enriched uranium) a separation method was developed. Iodine isotopes can be separated from a sodium hydroxide solution containing fission products using a column filled with alternate beds of glass microspheres and porous metal silver. Tests with tracers were performed in radiochemical laboratory. Following this results, a series of tests with higher activities (3 TBq of⁹⁹Mo and 0.7 TBq of¹³¹I) were carried out in hot cells. Molybdenum passes through the silver column, while¹³¹I retention was 92–97% in tracer test and 90% in optimised hot cell tests. This result depends on several facts that are discussed. An initial separation of iodine isotopes diminishes radiation damage on ion-exchange resin used in the subsequent molybdenum purification, improving its retention and elution yield.     

Production of fission 131I

Summary A method of iodine separation from other radionuclides generated by ²³⁵U fission has been developed in order to explore the possibilities to obtain ¹³¹I as by-product of the ⁹⁹Mo routine production in the Ezeiza Atomic Centre. The experiments were designed to remove this element to gas phase, and the recoveries were investigated both with and without carrier addition. High volatilization percentages were achieved in the presence of iodine carrier. Some other alternatives to increase the iodine displacement to the gaseous phase, namely vacuum distillation, addition of hydrogen peroxide and use of a carrier gas, were also studied. The method developed, which employs a carrier gas stream, without carrier addition, allows the recovery of about 97% of the ¹³¹I, with high specific activity, in a simple and clean way.     

Distribution of 131I-labeled recombinant human erythropoietin in maternal and fetal organs following intravenous administration in pregnant rats

The aim of the present study was to demonstrate the possible transplacental transmission of ¹³¹I labeled recombinant human erythropoietin (¹³¹I-rh-EPO) in pregnant rats and its distribution through maternal and fetal organs. Six Wistar Albino Rats in their pregnancy of 18 days were used ¹³¹I labeled recombinant human erythropoietin (specific activity = 2.4 μCi/IU) was injected into the tail vein of rats. After 30 minutes labeled erythropoietin infusion maternal stomach, kidney, lung, liver, brain and heart as well as fetus were removed. Then, the same organs were removed from each fetus. Measuring weight of maternal and fetal organs as well as placenta were followed by radioactivity count via Cd(Te) detector. ¹³¹I labeled recombinant human erythropoietin was found to be able to pass rat placenta and its distribution order in fetal organs was similar to those of maternal organs. Besides, as measurements were performed closer to cornu uteri, uptakes were decreasing in every fetus and its corresponding placenta.     

Iodine-129 in Missouri rain and milk

A combination of neutron activation and mass spectrometry was used to measure¹²⁹I and¹²⁷I in local samples of rain and milk. The general distribution of values for the¹²⁹I/¹²⁷I ratio in these samples can be understood in terms of well established geochemical and biological cycles of iodine, but the origin of high¹²⁹I/¹²⁷I ratios in a few of the samples collected in 1976 is not understood. The procedures used to extract and purify iodine were tested by monitoring¹³¹I in rain and milk following the Chinese atmospheric bomb test of September 17, 1977.     

131I标记海藻酸钠包裹明胶微球的制备及性能评价

建立了明胶微球和海藻酸钠(SA)包裹微球的制备方法,并通过实验比较了明胶微球和包裹微球的各种特性,最后用氯胺T法将125I及131I分别标记在微球上.结果表明,包裹微球对碘有更高的负载量和稳定性;在相同条件下,包裹微球的降解时间比明胶微球的降解时间长;将标记后的明胶微球通过直接注射介入到新西兰大白兔的肝脏,采用发射单光...     

Chlorination as a side reaction in radioiodination with chloramine-T

Chloramine-T is often used as an oxidizing agent for radioiodide in the electrophilic labeling of proteins and phenolic compounds. We have found that chloramine-T is also capable of introducing chlorine under the right conditions. Thus, treatment of fluorescein with no-carrier added¹²⁵I-sodium iodide and chloramine-T resulted in a uv-absorbing, fluorescent product in addition to the (no-carrier-added)¹²⁵I labeled material. The by product was tentatively identified as a chlorinated fluorescein by comparison with a known sample. The potential of macrochlorination should be kept in mind when using chloramine-T for radioiodination.     

A fast radiochemical procedure for separating iodine from fission products

The iodine isotopes produced by thermal neutron fission of²³⁵U were separated by a fast chemical procedure, with a separation yield of 95%. The gamma-ray energies and relative intensities in the decay of¹³¹I,¹³²I,¹³³I,¹³⁴I and¹³⁵I were determined using a Ge(Li) detector.     

Labeling of Sertraline with 131I and investigation of its radiopharmaceutical potential

Sertraline is an antidepressant drug. Sertraline was labeled with ¹³¹I by using iodogen method. Labeling yield was 85–90% and specific activity was approximately 64.75 GBq/mmol. The purification of radioiodinated Sertraline was performed by Sep Pak C-18 plus and the radiochemical purity was determined to be over 99%. Biodistribution studies were carried out by male Albino Wistar rats. The percentage of injected radioactivity per gram of tissue was calculated, and these data versus time curves were generated for organs and brain regions. The results showed that ¹³¹I labeled Sertraline may be a promising radiopharmaceutical for the investigation of serotonin 5-HT receptor functions of brain.     

Optimization of the preparation conditions of radioiodoepidepride: A dopamine D<Subscript>2</Subscript>receptor antagonist radioligand

Summary [¹²⁵I]iodepidepride, (s)-(-)-[(1-ethyl-2-pyrrolidinyl)methyl]-5-[¹²⁵I]-iodo-2,3-dimethoxybenzamide is the iodine substituted analogue of isoremoxipride, both of which are very potent dopamine D₂-antagonists. Epidepride was radioiodinated using different oxidizing agents such as chloramine-T, iodogen, iodogen glass frit and hydrogen peroxide. Chloramine-T is a powerful oxidizing agent compared to both iodogen and hydrogen peroxide so that the side products, especially the chlorinated epidepride, decreases the radiochemical yield. This chlorinated epidepride is minimized in the case of iodogen and iodogen glass frit and are not observed in case of the non-chlorinated oxidizing agent hydrogen peroxide. TLC and HPLC were used to analyze the reaction components and to estimate both the radiochemical yield and purity. The reaction parameters such as reaction time, pH, epidepride and oxidizing agent concentrations and the stabilty of the final product were studied to optimize the radiochemical yield and purity. The optimized radiochemical yield was about 90% and the radiochemical purity of the final product was 99.9%.     

Rapid determination of131I in environmental waters using a liquid anion exchanger

A rapid and specific method for the determination of¹³¹I in environmental water samples in the presence of some of the most important fission products is described. Radioiodine is separated from acidified water using tri-n-octylamine solution in toluene with dissolved iodine by one-stage static procedure with about 90% separation efficiency and 200-fold volume concentration. After the decolorization of the organic phase with NaOH in methanol, radioactivity of¹³¹I is counted by a toluene base liquid scintillator with a counting efficiency of 70%. The method is simple and enables to determine low radioactivity¹³¹I with a detection limit less than 5 pCi/1 in about 1.5 hrs.     

Biological distribution of iodo-allyl gabapentin and iodo-gabapentin

Gabapentin (GBP) is an anticonvulsant and is widely used in the treatment of epilepsy. In this study, GBP and an allyl derivative of GBP were radioiodinated with ¹³¹I using the iodogen method; then their radiopharmaceutical potential in rats and rabbits was investigated. The radiochemical purity of ¹³¹I-GBP and its derivatives was determined by RTLC. The labeling yield was 95±2%. Biological evaluation was performed in normal rats and rabbits. Labeled compounds were intravenously injected into two rabbits via the ear vein after anesthetizing. The dynamic and static scintigrams were obtained using a gamma camera at different time. Then the labeled compounds were administered intravenously into the rats. The distribution was studied by counting the radioactivity in the removed organs. The results of biodistribution in the rats showed the clearance of ¹³¹I-ALGBP was faster than ¹³¹I-GBP. On the other hand, the uptake of ¹³¹I-ALGBP in the brain was higher than ¹³¹I-GBP at 60 minutes.     

Comparison of the radiopharmaceutical potentials of dithizone radiolabeled with 131I and with 99mTc

In this study, dithizone (diphenylthiocarbazone) has been separately radiolabeled with ¹³¹I and with ^99mTc for preliminarily testing their radiopharmaceutical potentials on male albino rabbits. ¹³¹I-dithizone and ^99mTc-dithizone were intravenously injected to rabbits via their ear veins after anesthetizing with a mixture of Alfazyne and Alfamine (Serva) to determine their dynamic and static statuses in the metabolism. Also, ^99mTc as pertechnetate and ¹³¹I as iodate were administered to rabbits as controls. Dynamic and static scintigrams were obtained using a gamma camera (Diacan Instruments). Dynamic scintigrams were obtained over the first half hour with frames of 1 minute following the administrations of the labeled compounds. Static images were obtained from posterior projection at different time intervals up to about 3 hours following the administration of the radiolabeled compounds. ^99mTc-dithizone was significantly uptaken by the pancreas in contrast to free ^99mTc. In the case of ¹³¹I-dithizone, the distribution of ¹³¹I activity in the metabolism was clearly different than the case of free ¹³¹I and the uptake of ¹³¹I-dithizone at the pancreas zone was also significant. These preliminary tests have clearly indicated that especially ^99mTc-dithizone has a significant potential to be used as a pancreatic radiopharmaceutical.     

Application of 129I as an environmental tracer

¹²⁹I is produced naturally by cosmic-ray spallation of Xe and by spontaneous fission of ²³⁸U. In the environment ¹²⁹I is mainly due to nuclear weapon tests and reprocessing plants. The high water solubility of iodine makes ¹²⁹I a good oceanographic tracer. Long residence time and large air releases of ¹²⁹I from reprocessing plants allow ¹²⁹I to be used as a geochemical and metrological tracer. The same chemical and physical properties of ¹²⁹I and ¹³¹I enable one to use ¹²⁹I as a tool for the reconstruction of ¹³¹I doses after a nuclear accident. Some studies using ¹²⁹I as a tracer which were carried out in the author's laboratory, are summarized. This revised version was published online in July 2006 with corrections to the Cover Date.     

Immunoradiometric assay for the in-vitro determination of thyroid stimulating hormone in human serum and plasma using solid phase anti-TSH cellulose particles

Summary Development, optimization and validation of immunoradiometric assay (IRMA) using solid phase-cellulose particles for the measurement of TSH in human serum or plasma are described. The preparation of ¹²⁵I anti-TSH monoclonal antibody (MoAb) was carried out by two different methods (Chloramine-T and Iodogen). It was found that Ch-T method gave approximately the same results as the iodogen method. The activation of cellulose particles using 1,1-carbonyl diimidazole (CDI) and coupling of these solid phase particles with sheep anti-TSH were carried out. Optimization and validation of the assay were undertaken. The reproducibility as measured by the intra- and inter-assay variations is acceptable. The recovery and dilution tests indicated accurate calibration and appropriate matrix. No significant position effect was recognized. The different modes of sampling tested did not affect significantly the results of the present study. The present technique agreed well with the currently used commercial kit (DPC, IRMA). The cellulose particles of the present system for estimation of TSH retain their characteristics during storage for 6 months at 4 °C. In conclusion, this technique proved to be sensitive, specific, precise and accurate for routine laboratory use.     

Synthesis of radioiodinated 4-[*I]iodoantipyrine via isotopic exchange

Radioiodinated 4-[*I]iodoantipyrine labeled with radioiodine (i.e., ¹²³I or ¹²⁵I or ¹³¹I) has been used for modeling radiation damage on cell nuclei of tumor cells where the characteristic high linear energy transfer (high-LET) of the Auger electron could be demonstrated. Also, the compound is currently used for the measurement of regional cerebral blood flow (rCBF) in autoradiography. 4-[¹³¹I]iodoantipyrine was synthesized by two methods via a nucleophilic isotopic exchange reaction between ¹³¹I as iodide ion [¹³¹I^–] and inactive 4-[¹²⁷I]iodoantipyrine: either in absolute ethyl alcohol catalyzed by ammonium acetate or in dry state molten ammonium acetate (m.p. 114 °C) as an isotopic exchange medium without carrier addition. The first one is called wet method: where a solution of 4-iodoantipyrine and ammonium acetate in absolute ethyl alcohol and lyophilized Na¹³¹I was heated briefly up to boiling (80 to 90 °C) for 30 minutes under reflux. The second one is called dry state-molten method: where the alcoholic solution containing 4-iodoantipyrine and ammonium acetate and the lyophilized Na¹³¹I were heated briefly in a nitrogen stream to dryness at 120 to 125 °C for 5 minutes or melted by gradual heating at 150 to 160 °C for 5 minutes. A radiochemical yield ranged between 90%–95% in each method has been obtained for 4-[¹³¹I]iodoantipyrine. In both methods, the reaction proceeds properly without carrier addition by an addition – elimination mechanism. The physico-chemical parameters affecting the radiochemical yield of the isotopic exchange reaction [i.e., reaction time, temperature, exchange medium, concentration of the reactants, carrier (KI) addition and pH] were investigated. Chromatographic analysis i.e., TLC and HPLC were used to determine the radiochemical yield as well as the purity of the final product, which was as pure as 99.9%.     

Labeling of diazepam with iodine-131

Diazepam, which aims at benzodiazepine receptors and can be used as a specific SPECT agent has been labeled with [¹³¹I]2-iododiazepam (2-IDZ) was obtained in 50% HCl medium and [¹³¹I]2-iododiazepam (2-IDZ) was prepared by the iodogen method. The products were purified by passing through a Dowex-1 anion-exchange column.