Study of the conditions for ibuprofen labeling with 125I to prepare an inflammation imaging agent

A procedure was developed for radioiodination of ibuprofen with ¹²⁵I via an electrophilic substitution reaction. With the aim to optimize the labeling conditions and obtain a high radiochemical yield of ¹²⁵I-ibuprofen (¹²⁵I-Ibup), the effect exerted on the process by the reaction conditions (ibuprofen concentration, pH, reaction time, temperature, oxidizing agent) was studied. With 3.7 MBq of Na¹²⁵I, 100 μg of ibuprofen as substrate and 100 μg of iodogen as oxidizing agent, with the reaction performed in ethanol at 60°C for 10 min, the maximum radiochemical yield of ¹²⁵I-Ibup (78%) was obtained. The labeled compound was separated and purified to remove inactive ibuprofen by HPLC. The biological distribution in normal and inflamed mice shows that radioiodinated ibuprofen is suitable for imaging of inflammation only induced with turpentine oil.     

Radioiodination of pindolol as a β-adrenergic receptor using different oxidizing agents

A simple, fast, and efficient method was developed for preparing radioiodinated ¹²⁵I-pindolol (¹²⁵IPIN) using different oxidizing agents. ¹²⁵I-PIN was prepared by the reaction between Na¹²⁵I and pindolol using iodogen, Chloramine-T, N-bromosuccinamide, or H₂O₂ as an oxidizing agent at pH 7. The reaction proceeds well within 30 min at room temperature (20–25°C). The radiochemical yield was determined by TLC using chloroform-acetic acid-water (15: 4: 1) as developing solvent and by HPLC using reversed-phase RP18 column and acetonitrile-0.1 M ammonium bicarbonate (pH 7.5) (1: 1) as the mobile phase at a flow rate of 1 mL min^?1. The radiochemical yield with the above oxidants was found to be 85, 93, 96.5, and 97.5%, respectively, with the radiochemical purity of ¹²⁵I-PIN over 99.9%.     

Preparation and preclinical evaluation of radioiodinated secnidazole as a possible tumor imaging agent

To develop a radiopharmaceutical localizing in tumor hypoxic tissues, secnidazole (SECN) was labeled with ¹²⁵I. The labeled product was prepared with the radiochemical yield higher than 96% when performing the reaction at 45°C for 30 min. The electrophilic radioiodination of SECN was done using different oxidizing agents. Iodogen appeared to be more effective than chloramine-T (CAT) and N-bromosuccinimide (NBS). ¹²⁵I-SECN was tested in vivo with a tumor model prepared by the intramuscular injection of Ehrlich cell line into the thigh muscle of mice. ¹²⁵I-SECN showed high accumulation in tumor hypoxic tissue (3.6% of injected dose per gram of organ at 2 h post injection). The target/nontarget (T/NT) ratio was high (T/NT = 6 at 24 h post injection). Thus, radioiodinated SECN shows promise as a selective imaging agent for diagnosis of tumor hypoxia.     

Radioiodination and biological evaluation of salbutamol as a β2-adrenoceptor agonist

A procedure for preparing high-radiochemical-purity ¹²⁵I-salbutamol was developed in order to characterize the binding properties of ??₂-adrenoceptors. Direct radioiodination of salbutamol was carried out using Chloramine T as an oxidizing agent. The optimized conditions for salbutamol labeling with ¹²⁵I are as follows: 100 ??g of salbutamol, 50 ??g of Chloramine T, 150 ??l of phosphate buffer (pH 7), room temperature (25 ± 1°C), 5 min. The radiochemical yield of up to 98% was attained. The radiochemical yield and purity of the labeled product were evaluated by electrophoresis and HPLC. Biodistribution studies were carried out in normal Albino Swiss mice at different time intervals after administration of ¹²⁵I-salbutamol. The results indicate that the labeled compound cleared from the systematic circulation within 3 h after administration and majority of organs showed significant decrease in the ¹²⁵I-salbutamol uptake. The heart and lung uptake was high. ¹²⁵I-Salbutamol can be used as ??-receptor imaging agent.     

Preparation of radioiodo-metoprolol and its biological evaluation as a possible cardiac imaging agent

¹²⁵I-Metoprolol was prepared by electrophilic substitution reaction in the presence of Chloramine-T (CAT) as an oxidizing agent. The reaction conditions were optimized. The radiochemical yield of ¹²⁵I-metoprolol exceeding 90% was attained in 10 min at ambient temperature (25 ± 1°C). The radiochemical yield and purity of the labeled product were evaluated by electrophoresis, thin-layer chromatography (TLC), and high-performance liquid chromatography (HPLC). Biodistribution studies of ¹²⁵I-iodometoprolol were carried out in normal Albino Swiss mice. The results indicate the possibility of using [¹²⁵I]-iodometoprolol for myocardial imaging.     

Electrophilic iododestannylation of <Emphasis Type="Italic">N</Emphasis>-(4-(2-azanorborn-2-yl)butyl)-4-trimethylstannylbenzamide as a route to a novel radioiodinated compound for malignant melanoma

N-(4-(2-Azanorborn-2-yl)butyl)-4-[¹²⁵I]iodobenzamide was prepared by the reaction of its trimethylstannyl precursor with Na¹²⁵I in the presence of various oxidizing agents such as lactoperoxidase, Chloramine T, and Iodogen. The effect of reaction parameters such as temperature, reaction time, oxidizing agent concentration, pH, and substrate concentration was examined. The stability of the labeled product was evaluated. Chromatographic analysis of the reaction mixture by TLC using ethanol: ethyl acetate (1: 1) and by HPLC using methanol: water (55: 45) as eluent showed that the optimum radiochemical yield of the final product is 94% and the radiochemical purity is 99%. Also HPLC chromatographic analysis showed that the content of undesired by-products, especially of chlorinated products, in case of Chloramine T was higher than that in case of other oxidizing agents. With the lactoperoxidase method, the amount of undesired by-products was minimal and, therefore, the radiochemical purity was high.     

Preparation and biodistribution of radioiodinated analgin as a possible inflammatory imaging agent

Direct radioiodination of analgin with ¹²⁵I was carried out using chloramine-T as an oxidizing agent. The labeling conditions were optimized. When performed with 50 μg of analgin and 10 μg of chloramine-T at pH 9 for 15 min at room temperature, the reaction gives 97.5 ± 1.2% radiochemical yield of ¹²⁵I-analgin. The radiochemical yield of the final product was determined by electrophoresis and HPLC. Biodistribution studies were carried out in normal Albino Swiss mice and in those with septic and aseptic inflammations at different time intervals after administration of radioiodinated analgin. It was found that radioiodinated analgin differentiates between septic and aseptic inflammations and can be used to detect inflammation.     

Radioiodination of 3-amino-2-quinoxalinecarbonitrile 1,4-dioxide and its biological distribution in Erhlich ascites cancer bearing mice as a preclinical tumor imaging agent

3-Amino-2-quinoxalinecarbonitrile 1,4-dioxide (QN) was labeled with ¹²⁵I, and the biological distribution of the product was studied. ¹²⁵I-QN was prepared by direct electrophilic substitution reaction using N-bromosuccinimide (NBS) as an oxidizing agent. The radiochemical yield of 92% was reached under the following optimum conditions: pH 7, 15 min, 100 μg of QN, and 75 μg of NBS. The labeled QN was stable for up to 12 h post labeling. Biodistribution study of ¹²⁵I-QN in tumor-bearing mice reflected that it accumulated in tissues with high proliferation rate with preferential accumulation in tumor sites. ¹²⁵I-QN was incorporated rapidly in the tumor site (T/NT = 4 at 2 h post injection), and then its content slowly decreased, whereas in the other tissues it decreased rapidly. The results obtained encourage the use of ¹²³I-QN as a tumor imaging agent.     

Radiolabeling of alpha-fetoprotein monoclonal antibody for detection of liver tumor

Radiolabeling of alpha-fetoprotein monoclonal antibody (AFP-MoAb) with ¹³¹I for detection of liver tumor was performed. Liver tumor in Japanese quails was induced by aflatoxin B₁, which is potent carcinogen to animals and birds. The labeling of AFP-MoAb was carried out using chloramine-T as oxidizing agent. The effect of the oxidizing agent amount, substrate amount, reaction time, and pH of the reaction medium on the product yield was studied. The labeled compound was quantitatively separated and purified by HPLC. The biodistribution of ¹³¹I-AFP-MoAb was studied upon oral administration of the tracer in both normal and tumor-bearing Japanese quails. Localization of ¹³¹I-AFP-MoAb in liver tumor indicates that this labeled compound can be used for radioimmunodetection of liver tumor.     

Conditions for dissolution and radiochemical isolation of U and Th from baddeleyite

Conditions of baddeleyite dissolution were examined, and an optimal method of its complete breakdown was found. A solution of ²²⁹Th tracer was prepared and used for radiochemical isolation of Th from baddeleyite. Radiochemical methds were developed for recovering the uranium and thorium fractions from a baddeleyite solution. The total chemical yield of U and Th was 71 ± 5 and 89 ± 7%, respectively.     

Immunoradiometric Assay for In Vitro Determination of Prostate Specific Antigen (PSA) in Human Serum Using Solid Phase Anti-PSA Coated Tubes

An immunoradiometric assay (IRMA) procedure for estimation of prostate specific antigen (PSA) using coated tubes was developed, optimized, and validated. ¹²⁵I-PSA and ¹²⁵I-anti-hPSA tracers were prepared using iodogen and lactoperoxidase methods, respectively. Production of polyclonal anti-PSA was carried out using four New Zealand rabbits as a host. The polyclonal antibody was purified using caprylic acid/ammonium sulfate precipitation method. The coating was performed using the purified polyclonal antibody. The assay is highly sensitive and accurate.     

Use of polymeric materials as a solid phase for radioimmunoassay and immunoradiometric assay techniques

Poly(acrylamide-acrylic acid-acrylonitrile)-ferrous sulfate, p(AM-AA-AN)-FeSO₄·7H₂O, resin was used as a solid phase for estimation of thyroid stimulating hormone (TSH) by radioimmunoassay (RIA) and immunoradiometric assay (IRMA) techniques. Comparison with cellulose particles as a known polymer solid phase was made. The tracers for RIA and IRMA were prepared by radioiodination of TSH antigen and TSH monoclonal antibody, respectively, using Iodogen as oxidizing agent. The tracers were purified by gel chromatography on Sephadex G-25 column. The polyclonal anti-TSH antibody was prepared via immunization of three white New Zealand rabbits with highly purified TSH antigen. The polymer was prepared by addition of aqueous solution of comonomer (AA-AN) and FeSO₄ as cross-linker to polyacrylamide p(AM) and irradiation of the mixture at ambient temperature in a ⁶⁰Co γ-cell. The polymer prepared and cellulose particles were activated using 1,1-carbonyldiimidazole, and these activated particles were coupled with the polyclonal TSH antibody. Optimization and validation of the RIA and IRMA techniques were made.     

Synthesis and characterization of a {ReO}3+ complex with S- and N-donor ligands and of its 99m Tc analog

A novel mixed-ligand ^99m Tc complex with mercaptobenzothiazole (mer) as ligand and aminothiazole (amino) as coligand was prepared and evaluated as potential brain radiopharmaceutical. Preparation at tracer level was accomplished by substitution, using ^99m Tc-gluconate as precursor and a coligand/ligand ratio of 5. Under these conditions, the labeling yield was over 97% and the major product with radiochemical purity >97% was isolated by HPLC and used for biological evaluation. The reaction of [ReO(Citrate)₂]^? with mer and amino in hot MeOH yields [ReO(mer)(amino)OH(H₂O)₂]. The DFT study demonstrated that the complex contains distorted octahedral ReO(V). The Re coordination sphere consists of the terminal oxo group, the S donor atom of the deprotonated mer, the N atom of the deprotonated amino, OH group, and two water molecules. Biodistribution in mice demonstrated early brain uptake, fast blood clearance, and excretion through hepatobiliary system. Although the brain/blood ratio increased significantly with time, the novel ^99m Tc complex did not exhibit ideal properties as brain perfusion radiopharmaceutical since brain uptake was too low.     

Radiolabeling and biological evaluation of losartan as a possible cardiac imaging agent

A procedure was developed for preparing high radiochemical purity ^99m Tc-Losartan in a yield of about 90%. The optimal reaction conditions are as follows: 100 μg of Losartan, 50 μg of SnCl₂·2H₂O, 150 μL of phosphate buffer (pH 7), room temperature (25 ± 1°C), reaction time 5 min. Under these conditions, the radiochemical yield up of ^99m Tc-Losartan reaches 98%. The radiochemical yield and purity of the labeled product were determined by electrophoresis and paper chromatography. Biodistribution studies were carried out in normal Albino Swiss mice at different time intervals after administration of ^99m Tc-Losartan. The labeled compound cleared from the systematic circulation within 3 h after administration, and the majority of organs showed significant decrease in the uptake of ^99m Tc-Losartan. The heart uptake of ^99m Tc-Losartan was sufficiently high for using this agent as myocardial imaging agent.     

Synthesis of 2-[18F]Fluoro-L-tyrosine and comparative study of its uptake by rat glioma 35 tumor and by induced inflammation focus in experimental animals

2-[¹⁸F]Fluoro-L-tyrosine (2-[¹⁸F]FTYR), a labeled fluorinated analog of tyrosine, was prepared using chiral phase-transfer catalysis. The radiochemical yield of 2-[¹⁸F]FTYR corrected for radioactive decay was 25±6% (n = 15) at a synthesis time of 110–120 min, including semipreparative HPLC purification. The radiochemical and chemical purity of the product exceeded 99%, and the enantiomeric purity was 98.2±0.7% (n = 15). The uptake of 2-[¹⁸F]FTYR by tumors and abscesses in laboratory animals was studied. The ratios of radioactivity uptake by tumor or imflamed tissue to that of an intact muscle tissue were calculated. Within the time of experiment, the tumor/muscle ratio exceeds the abscess/muscle ratio. The results obtained allow 2-[¹⁸F]FTYR to be considered as potentially useful radiotracer for differential diagnostics of tumors and inflammations by PET.     

Labeling of EGFR inhibitor to prepare a potential SPECT agent for molecular imaging of breast cancer via iodine-bromine exchange

A simple method was developed for labeling N-{4-[(3-chloro-4-fluorophenyl)amino]quinazolin-6-yl}-3-bromopropionamide, an EGFR inhibitor, with radioactive iodine via nucleophilic iododebromination. The factors affecting the radiochemical yield of ¹²⁵I-EGFR such as reaction medium, substrate concentration, CuCl concentration, and temperature were examined. Reducing agents such as ascorbic acid, SnCl₂, and Na₂S₂O₅ were used to prevent disproportionation. The radiochemical yield and purity of the labeled product were determined by TLC and HPLC.     

Synthesis of 99m Tc-L-carnitine as a model for tumor imaging

An L-carnitine derivative labeled with ^99m Tc was prepared. It is effective in tumor imaging. The labeling was done using SnCl₂ as a reducing agent. The optimum conditions required to label 25 ??g of L-carnitine were as follows: 100 ??g of SnCl₂, 30 min reaction time, room temperature, pH 7 (0.5 M phosphate buffer). The radiochemical purity of the labeled compound was determined by paper chromatography. The yield was about 93%. About 2.5 × 10⁶ Ehrlich ascites carcinoma (EAC) cells were injected intraperitoneally to produce ascites and intramuscularly in the right thigh to produce solid tumor in female mice. Biodistribution studies were carried out by injecting a solution of ^99m Tc-L-carnitine into normal and tumor-bearing mice. The uptake in ascites and in solid tumor was over 5% of the injected dose per gram tissue at 4 h post injection. These data revealed localization of the tracer in the tumor tissues with high percentage sufficient to use ^99m Tc-L-carnitine as a promising tool for diagnosis of tumor.     

Synthesis of <Superscript>177</Superscript>Lu-based bioconjugate for radioimmunotherapy and evaluation of its stability in physiological media

Labeling of the conjugated molecule of human serum albumin (HSA) and humanized scFv 4D5 mini-antibody specific to her-2/neu receptor with β-emitting ¹⁷⁷Lu radionuclide via p-SCN-benzyl-DTPA chelator was studied. The radioconjugate can be prepared with the decay-corrected radiochemical yield of 82%. The stability of the synthesized complex in physiological solutions (normal saline, human blood serum) was evaluated. The complex is stable in physiological solutions for no less than 10 days.     

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.     

Cyclotron production and radiochemical isolation of the therapeutical radionuclide 186Re

The reaction cross sections and the energy dependences of the yields of ¹⁸⁶Re in the reactions ^natW(d, 2n) and ¹⁸⁶W(d, 2n) in the range of low deuteron energies (<14 MeV) were determined. The specific features of the physicochemical behavior of impurity ¹⁸⁶Re atoms in irradiated tungsten cyclotron targets were studied in relation to the gas medium composition. The yield of the desired product increases with an increase in the oxygen content in the course of heat treatment of the targets. A simple “dry” procedure was developed for isolation of ¹⁸⁶Re with a yield no less than 85% and radiochemical purity no worse than 99.99%. A proto-type of a cyclotron target for commercial production of the therapeutical radionuclide ¹⁸⁶Re was suggested.