Synthesis of <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc-Radiolabeled Uridine as a Potential Tumor Imaging Agent

Uridine, a pyrimidine nucleoside essential for the synthesis of RNA and biomembranes, was radiolabeled with ^99mTc to obtain a potential tumor imaging agent. The maximal radiochemical yield of about 96.5%, as determined by paper chromatography and instant thin-layer chromatography, was reached under the following optimum conditions: 1 mg of uridine, 20 μg of SnCl₂·2H₂O as reducing agent, 20 mg of mannitol as a stabilizer, and pH 8. ^99mTc-uridine is stable in vitro at room temperature for up to 6 h post labeling. The biodistrbution study in tumor-bearing mice shows high target-to-nontarget ratio. These results match with the high docking score of the complex on uridine phosphorylase enzyme. ^99mTc-uridine shows promise as a tumor imaging agent.     

Labeling and biological evaluation of <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc-tricarbonyl-chenodiol for hepatobiliary imaging

^99m Tc-tricarbonyl-labeled chenodiol (chenodeoxycholic acid, CDCA) intended for hepatobiliary imaging was prepared by 30-min heating at 100°C with a radiochemical yield of >98%. The radiolabeling yield and stability of the complex were evaluated using different chromatographic techniques. Biodistribution studies in Albino Swiss mice at different time intervals after administration of the complexes showed that the maximum uptake of the complexes in the liver was 35.5 ± 0.25% ID/g at 30 min post injection. ^99m Tc-tricarbonyl- CDCA shows promise for hepatobiliary imaging.     

Comparative Biological Evaluation of <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc-Timonacic Acid Prepared Using Different Reducing Agents as a Complex for Hepatobiliary Imaging

Timonacic acid (TCA) was labeled with ^99mTc in the presence of three different reducing agents: NaBH₄, Na₂S₂O₄, and SnCl₂·2H₂O. The optimum conditions were as follows: with Na₂S₂O₄, pH 8, 7 mg of Na₂S₂O₄, room temperature, 2 mg of TCA, 30 min (radiochemical yield 98 ± 0.3%, complex was stable for 24 h); with NaBH₄, pH 8, 10 mg of NaBH₄, room temperature, 2 mg of TCA, 30 min (radiochemical yield 95 ± 0.3%, complex was stable for 6 h). The biodistribution of the complex in mice was studied. The liver uptake depends on the reducing agent used, reaching in 30 min 33.5 ± 0.3, 18.4 ± 0.18, and 22.3 ± 0.3% ID/g for the complexes prepared using Na₂S₂O₄, NaBH₄, and SnCl₂·2H₂O, respectively.     

Formulation and Biodistribution of <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc-Dacarbazine,a Radioligand for Neoplasm Imaging

A method for preparing ^99mTc-Dacarbazine, a potential cancer diagnostic agent, was developed. The method is based on direct labeling of Dacarbazine with ^99mTc in the presence of stannous chloride as reducing agent. The reaction conditions were optimized to obtain the radiochemical yield of ^99mTc-Dacarbazine higher than 90%. The biodistribution of ^99mTc-Dacarbazine in normal and tumor-bearing Albino Swiss mice was studied. ^99mTc-Dacarbazine has a high tumor affinity and shows promise for cancer imaging. Quantitative relationship between the optimized structures and computed molecular properties related to Dacarbazine binding sites was analyzed using molecular modeling.     

Preclinical evaluation of <Superscript>99<Emphasis Type="Italic">m</Emphasis> </Superscript>Tc-histidine as a possible tumor imaging agent

Radiolabeling of histidine (Hist), an essential amino acid, with ^99mTc was performed. The radiochemical yield higher than 95% was achieved with stannous chloride as a reducing agent. Factors affecting the radiochemical yield (histidine amount, stannous chloride amount, reaction time, pH of the reaction mixture) were studied in detail, and the reaction conditions were optimized. In vitro stability of the radiolabeled complex was checked, and it was found to be stable for up to 6 h. ^99mTc-Hist was injected intravenously into normal and tumor-bearing mice. Biodistribution studies revealed that the ^99mTc-Hist uptake in tumor sites was 10 and 16% ID/g in ascites and 7 and 9.2% ID/g in thigh solid tumor at 60 and 120 min post injection, respectively. The amount of ^99mTc-Hist in ascites and solid tumor increased with time and then decreased slowly. Thus, ^99mTc-Hist can be used as a potential agent for imaging tumor sites.     

Synthesis and Stability of New Nitrophenol Complexes of <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc as Possible Hypoxia Imaging Radiopharmaceuticals

Seven new nitrophenol derivatives were synthesized; their ^99mTc complexes (N₂OS chelates), which are possible hypoxia tumor imaging agents, were prepared by the reaction with [^99mTc]NaTcO₄ in the presence of SnCl₂ at pH 10. The in vitro biostabilty of the complexes was evaluated. The purity and stability (in human and rat serum) of the complexes were evaluated by chromatographic methods (TLC, HPLC). The most stable (for more than 6 h) is the complex of ^99mTc with 3-[3′-N-(2″-hydroxy-5″-nitrobenzylamino)-2′-hydroxypropyl]-1-methylthiourea.     

Radiochemical and biological characterization of <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc-oxiracetam as a model for brain imaging

^99mTc-oxiracetam was prepared. It can be used as a radiotracer for brain imaging. Under the optimum conditions (0.5 mg of oxiracetam, 50 μg of SnCl₂·2H₂O, pH 7, room temperature, 30 min), the radio-chemical yield determined by chromatographic methods reached 96%. Biodistribution studies with mice showed that the brain uptake of the complex was 5.1% injected dose per gram (% ID/g) at 5 min post injection. In this parameter, the complex surpasses the commercially available ^99mTc-ECD (4.7% ID/g) and ^99mTc-HMPAO (2.25% ID/g).     

Preparation and biological evaluation of <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc-timonacic acid as a new complex for hepatobiliary imaging

Timonacic acid (TCA) was successfully labeled with ^99m Tc. The influence exerted on the reaction by the substrate and reducing agent concentrations, pH of the reaction mixture, and reaction time was examined, and in vitro stability of ^99m Tc-TCA was evaluated. The maximum labeling yield was 98.5 ± 0.6%. The complex was stable throughout the working period (6 h). A study of in-vivo biodistribution in mice showed that the maximum uptake of ^99m Tc-TCA in the liver was 22.3 ± 0.3% of the injected activity per gram of the tissue or organ (% ID/g) at 30 min post injection. The clearance from the mice appeared to proceed via the circulation mainly through the kidneys and urine (approximately 56% of the injected dose at 1 h after injection). The liver uptake of ^99m Tc-TCA is higher than that of ^99m Tc-UDCA (ursodeoxycholic acid); therefore, ^99m Tc-TCA shows more promise for liver SPECT.     

Design,synthesis, <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc labeling,and biological evaluation of a novel pyrrolizine derivative as potential anti-inflammatory agent

The design and synthesis of ethyl 4-(6-amino-7-cyano-2,3-dihydro-1H-pyrrolizine-5-carboxamido)-benzoate (KH16) were discussed, and its structure was determined. The anti-inflammatory activity of a new compound was evaluated using in vitro cyclooxygenase (COX) inhibitory assay. KH16 exhibits higher selectivity to COX-2 than to COX-1 with the selectivity index of 3.46. KH16 was labeled with ^99mTc with the maximum radiochemical yield of ^99mTc-KH16 of 90.5 ± 1.5%. Biodistribution of ^99mTc-KH16 in normal, infected, and inflamed mice was studied. The uptake in inflamed muscle was higher than that in normal muscle throughout the examined time interval. This work is a step ahead in the direction of using pyrrolizine derivatives for site-specific delivery to the inflamed tissue.     

Optimized chromatographic separation and biological evaluation of <Superscript>99<Emphasis Type="Italic">m</Emphasis> </Superscript>Tc-clarithromycin for infective inflammation diagnosis

Clarithromycin antibiotic was labeled with technetium-99m by adding ^99mTc to clarithromycin in the presence of SnCl₂·2H₂O. The radiochemical yield of ^99mTc-clarithromycin was determined by chromatographic methods. Gel chromatographic method was investigated for separation of the reaction mixture using different eluents including NaCl and phosphate, citrate, and carbonate buffer solutions. Also, free ^99mTcO₄^- and ^99mTc-clarithromycin were efficiently separated by reversed-phase HPLC on RP18 column. The maximum radiochemical yield reached 98 ± 0.2%. ^99mTc-clarithromycin is stable for 6 h. Biological distribution of ^99mTc-clarithromycin was studied for mice with the infection in the left thigh induced using Staphylococcus aureus. The target-to-nontarget (T/NT) ratio for ^99mTc-clarithromycin was found to be 7.33 ± 0.13 at 2 h after intravenous injection, with the subsequent gradual decline. This value is higher than that of commercially available ^99mTc-ciprofloxacin. The abscess to normal muscle ratio shows that ^99mTc-clarithromycin can be successfully used for infection imaging, allowing differentiation between bacterial infection and sterile inflammation.     

Sorption of Mo(VI) on zirconium molybdosilicate gel and potential application as a <Superscript>99</Superscript>Mo/<Superscript>99<Emphasis Type="Italic">m</Emphasis> </Superscript>Tc generator

Sorption of Mo(VI) from aqueous nitrate solutions onto zirconium molybdosilicate (ZrMoSi) gel was studied using ⁹⁹Mo radiotracer. The acid–base titration curve showed that the prepared ZrMoSi gel was an amphoteric material with the point of zero charge (PZC) at pH 2.5. The highest distribution coefficient (600 mL g^–1) of ⁹⁹Mo(VI) on ZrMoSi from nitrate media was achieved at pH 2.1. The sorption kinetics of ⁹⁹Mo(VI) onto ZrMoSi obeyed the pseudo-second-order model. The breakthrough sorption capacity of ZrMoSi gel was found to be 4.25 × 10^–2 [mmol Mo(VI)] g^–1. The prepared ⁹⁹Mo/^99mTc chromatographic column generator showed a good performance: The ^99mTc elution yield was 87.7%, pH of the eluate ranged from 5.6 to 7.2, and the radionuclidic purity of the eluted ^99mTc was >99.99% with a radiochemical purity of 98.31% (as ^99mTcO₄^–).     

Influence of Sn<Superscript>2+</Superscript> concentration on complexation of <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc with potassium sodium hydroxyethylidenediphosphonate

Kinetics of formation of a ^99m Tc complex with potassium sodium hydroxyethylidenediphosphonate (KNaHEDP) was studied. Since the Tc reduction competes with the Tc reoxidation at low Sn²⁺/Sn⁴⁺ concentration ratio, the reaction accelerates with increasing Sn²⁺ concentration from 1 to 10 μg ml^?1. At higher Sn²⁺ concentrations, Sn²⁺ ions have no effect on the complexation rate, since the concentration of reduced technetium becomes optimal for effective formation of the technetium complex with the ligand. More than 95% of ^99m Tc is bound into the complex at the Sn²⁺ concentration higher than 20 μg ml^?1. A high degree of Tc complexation is observed immediately after mixing the reactants and is maintained for 24 h. The rate and degree of ^99m Tc complexation with KNaHEDP are independent of the ligand concentration in the reaction mixture, varied from 5 to 10 mg ml^?1. At higher ligand concentration (25 mg ml^?1), the rate of formation of the ^99m Tc-KNaHEDP complex does not change, but its stability decreases.     

Radiodiagnosis of peptic ulcer with technetium-99<Emphasis Type="Italic">m</Emphasis>-labeled esomeprazole

Esomeprazole was labeled with ^99m Tc in high (up to ~98.0%) radiochemical yield. The optimum conditions are as follows: pH 8, 50 μg of SnCl₂·2H₂O, 30 min, and 2 mg of the substrate. The complex is stable for 8 h. The reaction mixture was separated by gel chromatography using such eluents as NaCl solution and, phosphate, citrate, and carbonate buffer solutions. Free ^99m TcO ₄ ^– and the complex were also efficiently separated by reversed-phase HPLC, paper chromatography, and electrophoreses. Intravenous biodistribution studies of ^99m Tc-esomeprazole complex showed high uptake in the stomach ulcer, reaching about 30.5% ID/g at 1 h post injection. Such a high ^99m Tc-esomeprazole uptake makes this agent promising for stomach ulcer imaging.     

Speed of sound in <Emphasis Type="Italic">n</Emphasis>-hexane, <Emphasis Type="Italic">n</Emphasis>-octane, <Emphasis Type="Italic">n</Emphasis>-decane,and <Emphasis Type="Italic">n</Emphasis>-hexadecane in the liquid state

This paper describes an improved experimental facility for measuring the speed of sound in liquids with an accuracy of up to 0.1%. Measurements of the speed of sound in liquid n-hexane, n-octane, n-decane, and n-hexadecane at temperatures of 298–433 K and pressures of 0.1–100 MPa have been made. It has been shown that in the possible comparison range the obtained values of the speed of sound are in good agreement with the literature data. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 732–736, July–August, 2008.     

The Activation Energy <Emphasis Type="Italic">U</Emphasis>(<Emphasis Type="Italic">T</Emphasis>,<Emphasis Type="Italic">H</Emphasis>) in Y-based Superconductors

Based on the Arrhenius equation, a method to calculate the activation energy from the resistance transition is proposed for high temperature superconductors. This method is applied to the Y-based superconductors. The activation energy is found to be U(T,H)∼(1−T/T _c )^4.8(H/H ₀)^−3.8 of YBCO crystal, and U(T,H)∼(1−T/T _c )^3.3(H/H ₀)^−2.2 of Er doped MTG YBCO crystal, respectively. With the obtained activation energy U(T,H), the lower part of the experimental curve ρ(T,H) and its derivative can be reproduced.      

Long-wavelength photodiodes based on <Emphasis Type="Italic">n</Emphasis>-GaSb/<Emphasis Type="Italic">n</Emphasis>-GaInAsSb/<Emphasis Type="Italic">p</Emphasis>-AlGaAsSb heterostructures

Photodiodes sensitive in the wavelength ranges 1–2.5 μm and 1–4.8 μm at room temperature have been created on the basis of n-GaSb/n-GaInAsSb/p-AlGaAsSb double-junction heterostructures of two types. The broadband photosensitivity of the diode structures of both types is indicative of the complete separation of photogenerated electron-hole pairs in the staggered n-p heterojunction (n-GaInAsSb/p-AlGaAsSb). The noise characteristics of photodetectors based on the proposed diode structures have been studied. Prospects of the use of these devices in thermophotovoltaic cells for low-temperature radiation sources are considered.     

Impact-ionization-stimulated electroluminescence in isotype <Emphasis Type="Italic">n</Emphasis>-GaSb/<Emphasis Type="Italic">n</Emphasis>-AlGaAsSb/<Emphasis Type="Italic">n</Emphasis>-GaInAsSb heterostructures

We have studied electroluminescence in n-GaSb/n-AlGaAsSb/n-GaInAsSb heterostructures with isotype heterojunctions, in which the quantum efficiency of emission is increased due to the additional production of electron-hole pairs as a result of the impact ionization that takes place near the heterointerface. The impact ionization in such heterostructures is possible due to the presence of deep wells in the energy band structure.     

Photosensitive point structures based on CuIn<Subscript>2<Emphasis Type="Italic">m</Emphasis> + 1</Subscript>Se<Subscript>3<Emphasis Type="Italic">m</Emphasis> + 2</Subscript> crystals

Photosensitive point structures based on CuIn_{2m + 1}Se_{3m + 2} (m = 0, 1, 2) single crystals have been obtained for the first time by means of electric-discharge welding (EDW). The stationary current-voltage characteristics and the photovoltaic properties of the structures based on CuInSe₂, CuIn₃Se₅, and CuIn₅Se₈ ternary semiconductors have been studied, which show evidence for the rectification effect and photoconversion. The character of interband transitions is established and the bandgap width variation in this series of compounds is traced. It is concluded that EDW can be successfully used for the fabrication of photoconverters based on multicomponent semiconductors.     

Advanced prospects for the preparation of zirconium [<Superscript>99</Superscript>Mo]molybdate(VI) gel from diluted reactants and <Superscript>99<Emphasis Type="Italic">m</Emphasis> </Superscript>Tc elution performance

Zirconium [⁹⁹Mo]molybdate(VI) gel (ZrMo) was prepared from dilute mixed solutions of zirconium oxychloride and [⁹⁹Mo]molybdate at pH 4.7. Paramolybdate(VI) anions were attracted to the positively charged surface of zirconia(IV) particulates (PZC at pH 7.2). The postulated reaction mechanism and gel formula were verified by radiometric analysis, X-ray diffraction, scanning electron microscopy, TGA, DTA, IR spectroscopy, and X-ray fluorescence analysis. ^99mTc elution from ZrMo dried at 50 and 200°C was investigated. Reproducibly high ^99mTc elution yield with high levels of radionuclidic, radiochemical, and chemical purity was achieved from the gel dried at 50°C. Correlation between structural properties of ZrMo and ^99mTc elution performance was discussed.