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.     

An oestrogen-derivative labeled with 99mTc and its radiopharmaceutical potential

An oestrogen derivative 3,17-a-oestradiolyl propyl 1,4,8,11-tetraazacyclotetradecanyl-1-(4-methylbenzoic acid)ester (ESTCPTA) that is 3,17-a-oestradiolyl propinol coupled to 1-(4-methylbenzoic acid)1,4,8,11-tetraazacyclotetradecane (CPTA) was synthesized in five steps. The product was purified by recrystallization in ethyl alcohol, and analysed by NMR and IR spectroscopy. ESTCPTA was labeled with ^99mTc and radio thin layer chromatography (RTLC) and radio-paper electrophoresis were used to determine the radiochemical yields. Specific activity was approximately 23.7 GBq/mmol and the labeling yield was over 95%. The biodistribution studies were performed on female Albino Wistar rats. The rats were sacricified by ether narcotization at certain time intervals and the activity of the organs was counted by a gamma counter. The activity per gram tissue was calculated and time activity curves were generated.     

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.     

Labeling of ornidazole with iodine-131

Ornidazole (1-(3-chloro-2-hydroxypropyl)-2-methyl-5-nitroimidazole) was labeled with iodine-131 by using iodogen method. Quality controls were performed by instant thin layer chromatography (ITLC) and electrophoresis methods. Labeling yield was 91%. Iodination was carried out by substitution of chloride by iodine-131. Structure was confirmed by¹H-NMR.     

Synthesis of DTPA-attached estradiol derivative and determination of its radiopharmaceutical potential

Summary An estrogen derivative, β-estradiol or 1,3,5,(10)-estratriene-3,17β-diol) attached to diethylenetriamine pentaacetic acid (DTPA) was synthesized in six experimental steps. At the end of these steps, a DTPA-attached estradiol derivative called deoxy-demethyl homoestradiolyl-diethylenetriamine-pentaacetic acid (ESTDTPA) was obtained. The synthesized compounds were labeled with ^99mTc. Thin layer radio chromatography (TLRC) was used to determine radiochemical yields and stabilities.Structural investigations confirmed the structures. The labeling yield was satisfactory (about 95%), and ^99mTc-ESTDPTA was stable in neutral medium at room temperature for 5 hours. Biodistribution studies were performed on normal and DMBA-induced, tumor bearing female Albino Wistar rats. The activity per gram tissue was calculated, and time-activity curves were plotted. ESTDTPA uptake by uterus reached a level of 20.73% dose/g, showing a maximum within 5 minutes after injection. Ovary and breast showed similar biodistribution profiles. The kidneys, which are the primary organs of metabolism and excretion of estrogen, showed a high ^99mTc-ESTDTPA uptake. The imaging studies were performed on normal and tumor bearing female Albino Wistar rats using a Camstar XR/T gamma-camera. Gamma-scintigraphy studies showed that tumors could be well visualized in a few minutes and clearly differentiated from other organs, such as bladder and liver by 24 hours.     

Labeling of acetaminophen with I-131 and biodistribution in rats

The aim of the present study was to label acetaminophen (APAP) with I-131 and to determine its radiopharmaceutical potential in rats. Acetaminophen was labeled with I-131 using the iodogen method. The radiochemical purity of (131)I-APAP was determined by RTLC and paper electrophoresis. The labeling yield was 94 +/- 4%. The biodistribution studies of the labeled compound (specific activity; 56.60 GBq/mmol) were performed in male Albino Wistar rats. The uptake of (131)I-APAP in some organs were determined at different time after injection to the rats. The radioactivity in each organ was counted and the percentage of injected activity per gram of tissue weight (%ID/g) for each organ and blood was calculated. (131)I-APAP uptake in the lung, liver, kidneys, pancreas, blood, stomach and some brain region, were observed. Thus, (131)I-APAP may be radiopharmaceutical for the imaging of the brain.     

Pyridylthiocarbazide complexes of rhenium with potential radiopharmaceutical applications

Attachment of a thioamide tethering group provides a modification of the well-known pyridylhydrazine based route to radiolabelling of biomolecules (the HYNIC system) and gives a proligand which gives stable, well-defined chelated derivatives with both Re(v) oxo and Re(III) diazenide cores. Both display previously unknown bonding modes for the pyridylthiocarbazide ligands.     

Specific activity determination and stability studies of therapeutic 131I-mIBG radiopharmaceutical

Board of Radiation and Isotope Technology, India is a manufacturer and supplier of therapeutic doses of the ¹³¹I-meta-iodobenzylguanidine to various nuclear medicine centers in India. The therapeutic dosage of radiopharmaceutical involves a single variable dose of >3.7 GBq activity. Since the radiopharmaceutical produced is mainly by isotope exchange, which yields a low specific activity product, the determination of its accurate mass is a critical parameter for its safe administration in patients. In view of this, a suitable high performance liquid chromatography (HPLC) method has been developed for the determination of specific activity with high precision. Also, quantification of stability in terms of the % radiochemical purity of the formulation >370 MBq/mL supplied, under different storage conditions over time was carried out using the developed HPLC method.     

Tricarbonylrhenium(I) complexes with anionic ligands containing S and O donor atoms – potential radiopharmaceutical precursors

Equilibrium geometry of tricarbonylrhenium(I) thiosalicylate and of methylthiosalicylate has been determined by the X-ray diffraction studies as well as calculated by the semiempirical method using the PM3 functional basis set. Infrared spectra of the species have also been studied in the 4000−800 cm⁻¹ range of wavenumbers. The experimental and theoretical data are in satisfactory agreement.     

Synthesis of a 99mTc labeled estrogen-derivative and the determination of its radiopharmaceutical potential on rats

An estrogen derivative 1-(3, 17-α-estradiolyl propin-1-yl-3-(1,4,8,11-tetraazacyclotetradecyl)-propanate (ESTACPA) was synthesized. The product was purified by HPLC and characterized by NMR and IR spectroscopy. The synthesized compound was labeled with ^99mTc. The biodistribution studies were performed on female Albino Wistar rats. The rats were sacrificed and their organs were removed. The radioactivities of the organs were counted using a gamma-counter. The activity per gram tissue was calculated and time versus activity curves were generated. The ^99mTc-ESTACPA uptake by the uterus and ovary such as ER-rich tissues, were observed. The pancreas and stomach also showed a significant uptake. This revised version was published online in July 2006 with corrections to the Cover Date.     

Labeling of apigenin with 131I and bioactivity of 131I-apigenin in male and female rats

Apigenin (4′,5,7-trihydroxyflavone), one of the most common flavonoids, has been shown to possess a variety of biological activities including tumor growth inhibition and chemopreventation. In the present study, apigenin was labeled with ¹³¹I using iodogen method and investigated of its bioactivity. Radiolabeling yield is 98±0.2%, as determined by radio thin layer chromatography (RTLC), electrophoresis and radio high performance liquid chromatography (RHPLC). Besides, structure analysis of synthesized cold iodoapigenin complex were assessed with LCMS/MS and ¹H-NMR. Results of in vitro study indicated a high stability (3 hours) in human serum. Biodistrubition studies are performed in male and female albino Wistar rats. Biodistribution data related to the male rats showed significant uptake in the small intestine. The female rats biodistribution results indicated that the uptake of ¹³¹I-apigenin was high in the intestine and uterus.     

Labeling of scorpion venom with 99mTc and its biodistribution

Labeling of scorpion venom (SV) was successfully achieved with ^99mTc using direct chelating method. Venom was labeled with ^99mTc using stannous chloride as reducing agent. Preliminary studies were done to establish the optimum conditions for obtaining the highest yield of the labeled venom. The labeling technique is effective, as a maximum labeling yield (97 %) was obtained after 30-min reaction time by using 80 μg SV in phosphate buffer of pH 7 and 25 μg Sncl₂·2H₂O at room temperature. Venom was injected into normal mice to determine the excretion pathway. Biodistribution studies in normal mice with SV shows rapid clearance of the venom from blood and tissue except for kidneys. The improvement of the immunotherapeutic treatment of envenomation requires a better knowledge of the biological actions of the SV since tissue distribution studies are very important for clinical purpose.     

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.     

First 97Ru complex with pyridine-2,6-dicarboxamide conjugate for potential use as radiopharmaceutical

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Cu(I) assisted radioiodination of hippuran with no carrier added131I

A study on the labeling of hippuran with no-carrier-added¹³¹I assisted by Cu(I) and excess of ascorbic acid is described. The role of ascorbic acid is to prevent the oxidation of Cu(I) to Cu(II) which activates the hydrolysis of o-iodohippuric acid to o-iodobenzoic acid. The use of Cu(I) allows an almost quantitative (97–99%) labeling yield to be obtained within 10–15 minutes at 100°C. The reaction is assumed to take place via the formation of an organocopper complex favoring the exchange reaction between radioiodine and inactive iodine in the hippuran molecule. The activation energy of the reaction was calculated to beE=12.2 kcal/mol.     

Synthesis and biodistribution of a novel 99mTc nitrido radiopharmaceutical with proline dithiocarbamate as a potential tumor imaging agent

In the present study, proline dithiocarbamate (PRODTC) ligand was radiolabeled with the [^99mTc≡N]²⁺ core successfully to obtain the ^99mTcN-PRODTC complex with high radiochemical purity. No decomposition of the complex at room temperature was observed over a period of 6 h. Its partition coefficient indicated that it was a hydrophilic complex. The electrophoresis results showed that the complex was negative. The biodistribution of ^99mTcN-PRODTC in mice bearing S 180 tumor showed that the complex accumulated in the tumor with a certain uptake. The tumor/blood and tumor/muscle ratios reached 2.19 and 4.54 at 2 h post-injection, suggesting it would be a promising candidate for tumor imaging.     

Quantum-chemical investigation of deoxypeganine and its salts I. Photochemical oxidation of deoxypeganine

Hypothetical models of the interaction of deoxypeganine molecules with a solvent have been considered by the MO LCAO quantum-chemical method in the AM1 approximation. Excited triplet states of deoxypeganine and its analogues have been calculated by the method of molecular interactions. A free-radical mechanism of photochemical oxidation has been proposed on the basis of the results obtained and of literature information.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 546–548, September–October, 1992.