Authors:A. El-Wetery, A. El-Mohty, and Kh. El-Azoney
A simple method for labelling of 16-Br-hexadecanoic acid (16-BrHDA) with radioactive iodine has been reported via nucleophilic131I-for-Br exchange in the dry state and in organic solvents. While preparation in some organic solvents such as acetic acid, dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) required reaction times of more than 2 hours to give yields of 20–50%, halogen exchange in dry state at temperature of about 100 °C gave rise to yields of about 94% of radiochemically pure 16-131IHDA within 5 min. The labelling product could be purified by high performance liquid chromatography (HPLC) and was shown to be free of significant radiochemical impurities.
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.
Improved radionuclide generator include a substantially insoluble salt of a radioactive parent which may be directly packed
in column for subsequent elution of the daughter radionuclide. An improved 188Re generator was prepared by reacting a radioactive tungsten (188W) as parent radionuclide incorporated with aluminum chloride to obtain an insoluble radioactive aluminum tungstate matrix.
The investigated matrix was characterized on the basis of the chemical composition, IR, thermal analysis and mechanical stabilities.
The factors affecting the elution performance were studied such as influence of pH, molar ratio and drying temperature. From
the obtained data, the molar ratio W:Al was 1.5:1 at pH = 4, the matrix dried at 105 °C for 2 h. Chromatographic and multichannel
analysis has been currently used to investigate the radiochemical and radionuclidic purity respectively on eluted 188Re. An elution yield more than 80%, with radiochemical purity <98% and radionuclidic purity <99% with a 188W break through >10−4% of the column. The Al+3 and W contents value were about 2 and 3 μg/mL eluate. The obtained data approved the stability of the prepared generator
and its suitability for medical application.
Authors:K. El-Azony, M. Ismail Aydia, and A. El-Mohty
Triton X-100 cerium(IV) phosphate (TX-100CeP) was synthesized and characterized by using IR, X-ray, TGA/DT and the elemental
analysis. The chemical stability of TX-100CeP versus the different concentrations of HCl acid was studied before and after
its exposure to the radiation dose (30 K Gray). The effect of HCl concentration on separation of Cr(III) from Cr(VI) by using
TX-100CeP as surface active ion exchanger was also studied. A novel method was achieved for the quantifying of Cr(III) and
Cr(VI) ions by using the high-performance liquid chromatography (HPLC) at wavelength 650 nm, a stationary phase consists of
reversed phase column (Nucleosil phenyl column; 250 × 4.6 mm, 5 μm), and a mobile phase consists of 0.001 M di-(2-ethylhexyl)
phosphoric acid (DEHPA) in methanol:water (70:30 v/v). The retention times were 7.0 and 8.5 min, for the Cr(III) and Cr(VI),
respectively. The exchange capacity of Cr(III) was quantified (2.1 meq/g) onto the TX-100CeP.
Authors:E. El-Ghany, A. El-Mohty, W. Zaghary, M. El-Kolaly, M. Raich, and A. El-Bary
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
Authors:A. El-Mohty, A. El-Wetery, M. El-Kolaly, and M. Raieh
A modified method for the preparation of L-[131/123I] iodotyrosine as a brain imaging agent is described. The method is based on direct electrophilic radioiodination of L-tyrosine with NaI [131/123I] using chloramine-T (CAT) and 0.001 g KI as a carrier at pH 7.0. The product was purified by reverse phase high performance liquid chromatography (HPLC). A high radiochemical yield up to 85% of L-[131/123I] iodotyrosine has been achieved with radiochemical purity of greater than 97%. The relation between the pKa of L-tyrosine and pH of the reaction medium was calculated in order to correlate the radiochemical yield of L-[131/123I] iodotyrosine and the state of the three ionizable groups of L-tyrosine. Also, the influence of the reaction conditions on the radiochemical yield of L-[131/123I] iodotyrosine was investigated.
Authors:S. El-Wetery, Kh.M. El-Azoney, E.A. El-Ghany, A.A. El-Mohty, and A. Deeb
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.
Authors:A. El-Mohty, M. El Kolaly, M. Raieh, H. Coenen, and G. Stocklin
L-3-[123I] iodo--methyltyrosine has been reported to have a high affinity for a transport system in the blood-brain-barrier (BBB). Synthesis of L-3-[123/131I] iodo--methyltyrosine was performed by direct electrophilic iodination starting with no carrier added (n.c.a)131I or123I in the presence of oxidizing agent. Different oxidizing agents have been tested and the different factors affecting the radiochemical yield of L-3-[123I] iodo--methyltyrosine have been investigated. A method of pharmaceutical preparation of L-3-[123I] iodo--methyltyrosine ready for medical applications has been described. Among the oxidizing agents tested, iodogen in phosphate buffer at pH 7 seems to be the best which gives high radiochemical yield (85%) within 5 minute reaction time at room temperature in the presence of small amount KI (0.001 g) as a carrier. The radioactive impurities and side chlorinated by-product which have been found in case of iodination by chloramine-T (CAT), KIO3 and H2O2 methods disappear in case of iodogen method. The labelled product was separated and purified by radio high pressure liquid chromatography (HPLC) using methanolwateracetic acid (20801) as eluant at a flow rate 1.0 ml/min. According to the signals of the detectors the fractions of L-3-[123I] iodo--methyltyrosine were collected, evaporated to complete dryness and the residue dissolved in isotonic phosphate buffer pH 7.4. The product was sterilized by passing through 0.22 m millipore filter and the radiopharmaceutical was now ready for nuclear medical application.
Authors:A. El-Mohty, M. El-Kolaly, M. Raieh, H. Coenen, and G. Stocklin
A method for radiopharmaceutical preparation of L-6-[123I]-iodo-m-tyrosine a potential SPECT brain imaging agent is described. The method is based on direct electrophilic radioiodination of L-m-tyrosine with [123I] NaI/chloramine-T (CAT) and small amount of KI as a carrier at pH 1.0 where L-6-[123I]-iodo-m-tyrosine is the predominant isomer. A high radiochemical yield of L-6-[123I]-iodo-m-tyrosine up to 70% has been achieved by adding small amount of KI (0.001 g) as a carrier to the reaction mixture. The pure 6-isomer was separated by reverse phase radio high pressure liquid chromatography (HPLC) on RP-18 column using 0.02M sodium acetate/ethanol (9010) adjusted to pH 3.9 with glacial acetic acid at a flow rate 2 ml/min. According to the signals of the UV detector (=254) the 6-isomer was eluted at a retention time 12.5 minutes,K=6. The eluted fraction of L-6-[123I]-m-tyrosine pooled together, evaporated under reduced pressure, then dissolved in 5 ml isotonic phosphate buffer and sterilized by passing through 0.22 m millipore filter. The sterile solution was now ready for nuclear medical applications. The biological distribution of L-6-[123I]-iodo-m-tyrosine in mice was studied. The results showed that 3% of the injected dose is taken up in dopamine rich striatum 30 minutes after injection and not in norepinephrine-rich hypothalamus.