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- Author or Editor: E. El-Ghany x
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Abstract
Although 125I-hydroxypindolol (125I-HYP) has been an excellent probe of adenoceptor function in certain tissues, but 125I-pindolol (125I-PIN) was found more specific for 
-adrenoceptor labeling. This study describes a fast and efficient method for radiolabeling of pindolol with iodine-125, where both chloramine-T and iodogen were used as oxidizing agents. The use of iodogen coated glass frit has a great advantage in increasing the radiochemical yield of 125I-pindolol and this was attributed to the increase of the interphaces boundary between the solid and liquid. This technique reduces the quantity of iodogen required to produce high radiochemical yield by its half. The radiochemical yield was determined by TLC system using chloroform: acetic acid: water (15:4:1) as developing solvent and by HPLC using reversed phase RP-18 column and acetonitrile: 0.1M ammonium bicarbonate pH 7.5 (1:1) as a mobile phase at flow rate (1ml/min). The radiochemical yield was found to be 48.6 and 62.9% respectively.
Abstract
Radioiodination of meta-iodobenzylguanidine (MIBG) by the isotopic exchange technique in the dry state has been performed. Benzoic acid, pivalic acid and acetamide have been used as molten protic media to promote isotopic exchange reactions. Ammonium sulphate, diammonium hydrogen ortho-phosphate and ammonium chloride were used as catalysts which provide acidic media to facilitate exchange reactions. Maximum radiochemical yields of 97.1±1.3% and 84.3±1.6% [131I] MIBG were obtained when ammonium sulphate and benzoic acid were used. High radiochemical yields of 88.3±1.1% and 74.4±1.5% [131I] MIBG were also obtained in case of diammonium hydrogen orthophosphate and pivalic acid which suggests their successful use as reaction media in the radioiodination of MIBG. The activation energy for the exchange reaction in ammonium sulphate was calculated to be 10.8 kcal/mole.
Abstract
We reported the synthesis and labeling of one tetradentate and two pentadentate amino-phenol ligands with technetium-99m by the direct pertechnetate addition and by ligand exchange methods. Labeling by direct pertechnetate addition was attended by adding pertechnetate eluate to the ethanolic solution of the amino-phenol ligands at pH 9. Stannous chloride dihydrate was used as reducing agent. Exchange studies were carried out via the use of the following 99mTc-chelates: 99mTc-DTPA, 99mTc-gluconate, 99mTc-tartrate and 99mTc-citrate complexes. Ligand exchange method was achieved by incubation the ligand solutions with 99mTc-co-ligands complexes in 0.05M bicarbonate buffer pH 9. At this pH value the 99mTc-co-ligands dissociated and the more stable new 99mTc-ligands were formed with high radiochemical yield 
95%. The radiochemical yield of 99mTc-labeled amino-phenol ligands were estimated by solvent extraction, electrophoresis and HPLC methods. The produced technetium-99m amino-phenol complexes were neutral, lipophilic and stable during the period of 24 hours.
Abstract
L,L-ethylenecysteine dimer (L,L-ECD) compound was synthesized with an overall yield 31.2% and a melting point 197–198°C. A systematic study has been carried out on the labelling of L,L-ECD with technetium-99m by ligand exchange via99mTc-EDTA. The percent labelling yield of L,L-ECD was found ≥95% when 0.75 2.0 mg and 100 μg of L,L-ECD, disodium-EDTA and tin (II) were used, respectively, at pH 5.5. The produced99mTc-L,L-ECD complex is stable, neutral and lipid soluble. The99mTc-L,L-ECD complex penetrate the blood-brain barrier following intravenous injection in the tail vein of mice with an initial brain uptake equal to 0.9% at 2 minutes and a slow washout equal to 0.65% after 25 minutes. High uptake in the gastrointestinal tract (GIT) was observed. It reaches up to 38.9% at 2 minutes and increased as time pass reaching 48.3% at 60 minutes. These results indicate that this ligand is suitable for brain imaging and has a tendency to be excreted via liver and GIT due to its lipophilicity.
Abstract
This paper adresses the development of a new radiopharmaceutical for cancer imaging and therapy. The optimization of the labeling of thymidine analogous, cytarabine, with 125I is described. High radiochemical yield and purity 
98% was obtained by reacting 50 mg cytarabine with 125I in the presence of iodogen as oxidizing agent and 0.5M phosphate buffer of pH 7 at 65 °C for 30 minutes. Preliminary in-vivo study was done in non-tumor bearing mice. The results revealed that this new tracer, 125I-cytarabine, has a high affinity to be localized in tissues of high proliferation rate, e.g., bone marrow 10%, 60-minute post administration. Also, the labeled compound was cleared quickly from most of the body organs and concentrated in bladder 55%, 60-minute post administration. These findings suggest that 125I-cytarabine, allows imaging and treatment of cancer. 125I-cytarabine meets most of the requirements to be used as a successful diagnostic and therapeutic agent: it is a low molecular weight molecule that diffuses readily in tissues, it will not induce an antibody response, thereby leading itself to repeated injection or continuous infusion.
Abstract
A rapid method for labelling of 1-phenyl 3-methyl 4-nitro 5-chloro pyrazole (5-Cl-MNPP) with radioactive iodide Na125I via 125I -for- Cl exchange has been reported. This method has been done in dry state (without catalyst and in presence of acetamide), in dimethyl formamide (DMF) as a solvent (without catalyst and in presence of tetrabutyl ammonium bromide (TBAB) as phase transfer catalyst (PTC)). In dry state, a trial to reduce the reaction temperature from 170 to 120 °C for the reaction between 5-Cl-MNPP and Na125I in presence of acetamide as a molten medium was tested. Using some organic solvents such as ethanol, dimethyl sulfoxide (DMSO), acetonitrile, and DMF, it was found that DMF gave low radiochemical yield of 5-125I-MNPP (25%) within 30 min. However, the addition of 1 mg of TBAB to DMF increased the radiochemical yield of 5-125I-MNPP from 25 to 95 within 30 minutes. The product 5-125I-MNPP was purified by reverse phase, high performance liquid chromatography (HPLC), with radiochemical purity of greater than 98.0%. The biodistribution of 5-125I-MNPP was demonstrated in normal mice through intravenous injection in the tail vein. The data show high uptake in the target organs equal to 2.5±0.22, 10.5±0.21, 4.3±0.27, 3.2±0.18 and 48.5±0.26 for brain, intestines, heart, kidneys and liver respectively. This indicates that, 5-125I-MNPP can be freely penetrate the blood brain barrier (B.B.B.) and can be expected its usefulness in the quantitative determination of cannabinoid receptor in the brain.
Summary
Indomethacin was successfully labeled with 125I. This labeling reaction was carried out via electrophilic substitution of hydrogen atom with the iodonium atom I+. The reaction was found to be strongly dependent on pH of the reaction medium. At neutral pH value, 7 the labeling yield was maximum. This may be due to the good solubility of indomethacin, good protonation and good working of the oxidizing agent at this pH value. Towards the acidic pH value, the yield decreased and towards the alkaline pH value the yield decreased due to the decomposition of the indomethacin. The labeling reaction is very fast but needs five minutes for completion. The produced 125I-indomethacin was found stable in-vivo as the thyroid gland uptake did not exceed 2%. Labeled indomethacin shows a good localization in inflamed muscle, either septic or sterile. It excretes mainly via liver and to some extent via kidney. The imaging must be carried out at 24-hour post injection, after that time, the background activity has cleared and the activity is concentrated in the target site.
Summary
Piroxicam was labeled effectively with 99mTc due to the presence of electron donating atoms such as sulfur, nitrogen, and oxygen in its structure. The labeling yield was found to be influenced by different factors such as the amount of piroxicam, stannous chloride dihydrate, pH of the reaction mixture, reaction time and reaction temperature. The suitable amount of stannous chloride dihydrate required to produce high labeling yield of 99mTc-piroxicam was 50 μg, above this quantity (200 μg) a colloidal solution was formed. Another factor which plays a significant role in this labeling reaction is the pH of the reaction medium. The labeling reaction was done only at alkaline pH range from 9-11, because piroxicam was not soluble at acidic or neutral pH. The labeling reaction proceeded well at room temperature and the complex was decomposed by heat. The labeled piroxicam (99mTc-piroxicam ) showed good localization in inflamed foci and good imaging must be taken at 24-hour post injection, as the ratio of both types of inflammation (sterile and septic) to the background are 10.6 and 8.7, respectively.
Summary
This investigation focused on the labeling of pefloxacin, a fluoroquinolone antibacterial agent, with 99mTc to form 99mTc-pefloxacin complex. The labeling process was done by direct addition of pertechnetate in isotonic solution to Sn-pefloxacin solution. The labeling technique is effective, as a high labeling yield (98%) was obtained after 30-minute reaction time. Different factors were found that influenced this labeling reaction: 0.5 mg pefloxacin or more must be used to prevent the formation of colloids in the reaction medium. Fifty micrograms of stannous chloride dihydrate were found to be sufficient to reduce all pertechnetate with activity ranging from 37 to 3700 MBq without the detection of free pertechnetate or colloids in the reaction mixture. The pH of the reaction medium was found to play an important role in the labeling process. The labeling reaction proceeds well at neutral pH (pH 6) but at acidic pH value (pH 4 or below) the yield of 99mTc-pefloxacin complex decreased markedly to a labeling yield of 5%. The reaction mixture must be heated to 100 °C in an oil bath to enhance the formation of the 99mTc-pefloxacin complex. The biodistribution data show that 99mTc labeled pefloxacin was retained in infectious focus. The retention was specific since the abscess uptake of 99mTc-pefloxacin remained high as compared to the uptake of aseptic foci at 24-hour post injection. Also, the clearance of the tracer from other tissues is rapid on the contrary to its clearance from the septic focus. This supports the hypothesis that 99mTc-pefloxacin is retained at the infectious site because of its specific binding to the gyrase enzymes of bacterial cells.
