Volume 102, Issue 6

The potential for production of the medically relevant 64 Cu has been investigated by proton irradiation of highly enriched 67 Zn targets. The excitation function of the 67 Zn( p ,  α ) 64 Cu a nuclear reaction was measured by the stacked-foil technique up to 30 MeV. The prediction of the TALYS code was also compared to the measured cross section results. Based on the improved database of the 67 Zn( p ,  α ) 64 Cu reaction, thick target yield as a function of energy was also deduced. Production possibility of 64 Cu is discussed in detail, employing different energy proton beams and with regards to the 61 Cu and 67 Cu contamination levels as a function of the target enrichment level. By using 1  μ A beam intensity, 6.3505 h irradiation time and enriched 67 Zn target ( 64 Zn ≤ 0.5%, 66 Zn ≤ 9%, 67 Zn ≥ 80%, 68 Zn ≤ 10% and 70 Zn ≤ 0.5%), the expected EOB (End Of bombardment) yields are 43.66, 88.80 and 156.14 MBq/ μ A at 12, 15 and 18 MeV proton energies, respectively. Application time-frames were also deduced where the total radio-copper contamination level remains below 1%.

Integral cross sections of the 64 Zn( n ,  p ) 64 Cu and 67 Zn( n ,  p ) 67 Cu reactions were measured for the fast neutron spectrum of TRIGA Mark-II reactor at Savar, Dhaka, Bangladesh. A clean radiochemical separation was performed to isolate the copper radionuclides from the target element zinc. The radioactivities produced in the irradiation were measured by HPGe γ -ray spectroscopy. The neutron flux over the energy range 0.5–20 MeV was determined using the 58 Ni( n ,  p ) 58 Co monitor reaction. The measured results amount to 28.9 ± 2.0 mb and 0.84 ± 0.07 mb for the formation of 64 Cu and 67 Cu, respectively. These values are slightly lower than the respective values for a pure fission spectrum. The present results were compared with data calculated using the neutron spectral distribution and the recently critically analysed excitation function of each reaction given in the literature. The good agreement validates the reliability of those excitation functions. The feasibility of simultaneous production of 64 Cu and 67 Cu with fast neutrons is discussed.

Solvent extraction studies of several actinide ions such as Am(III), U(VI), Np(IV), Np(VI), Pu(IV) were carried out from nitric acid medium using a synergistic mixture of N ,  N ′-diethyl- N ,  N ′-di(para)fluorophenyl-2,6-dipicolinamide, (DEtD(p)FPhDPA, DPA), and hydrogen dicarbollylcobaltate (H + CCD − ) dissolved in phenyltrifluoromethylsulphone (PTMS). The effects of different parameters such as aqueous phase acidity (0.01 – 3 M HNO 3 ), oxidation states of metal ions, ligand concentration, nature of diluent and temperature on the extraction behavior of metal ions were studied. The extracted Am(III) species was determined as H + [Am(DPA) 2 (CCD) 4 ] − . With increasing aqueous phase acidities, the extractability of both Am(III) and Eu(III) was found to decrease. The synergistic mixture showed better extraction in mM concentrations as compared to previously studied dipicolinamides. The thermodynamic studies were performed to calculate heat of extraction reaction and the extraction constants. The proposed synergistic mixture showed good extraction for all the metal ions, though lanthanide actinide separation results are not encouraging.

Nanocast ordered mesoporous carbons are attractive as sorbents because of their extremely high surface areas and large pore volumes. This paper compares Pu uptake, added as Pu(VI), to both untreated and chemically oxidized CMK-(carbon molecular sieves from KAIST) type mesoporous carbon with that to a commercial amorphous activated carbon. The CMK was synthesized via nanocasting by using cubic ordered mesoporous silica KIT-6 as a hard template, and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and nitrogen adsorption. A portion of the CMK was oxidized by treatment with nitric acid, and will be called OX CMK. The three carbon powders have similar particle morphology, and high BET surface areas. The activated carbon is disordered, while the CMK materials show large domains of ordered cubic mesostructure. The CMK material seems to have more oxygen-containing functional groups than the activated carbon, and the oxidation of the CMK increased the density of these groups, especially –COOH, thus lowering the point of zero charge (PZC) of the material. Batch studies of all 3 materials with plutonium solutions, in a 0.1 M NaClO 4 matrix were performed to investigate pH dependence, sorption kinetics, Pu uptake capacities, competition with ethylenediaminetetraacetic acid (EDTA) in solution, and Pu desorption. Both CMK materials demonstrated high Pu sorption from solutions of pH 3 or greater, and the oxidized CMK also showed high sorption from pH 2 solutions. The activated carbon bound less Pu, and at a much slower rate than CMK. All other batch experiments were carried out in pH 4 solutions. The Pu uptake from low-concentration solutions was faster for the oxidized CMK than for untreated CMK, but in more concentrated samples (∼250  μ M Pu), the Pu uptake kinetics and apparent capacity were the same for oxidized and untreated CMK. The 23-h Pu uptake capacity of the CMK materials was measured to be at least 58 ± 5 mg 239 Pu per g CMK carbon, compared to 12 ± 5 mg 239 Pu per g activated carbon. The presence of EDTA in solution decreased the Pu sorption to CMK. Desorption from all samples occurred in 1 M HClO 4 , usually within 24 h. The Pu interaction with the carbon surface was also probed via X-ray absorption spectroscopy (XAS) on the Pu L III absorption edge. Spectral fits of the X-ray absorption near-edge structure (XANES) data collected on both types of CMK samples showed that Pu(VI) was reduced to Pu(IV) at the carbon surface. The high affinity of mesoporous carbon for Pu, and the spontaneous reduction of Pu(VI) or Pu(V) to Pu(IV) at these carbon surfaces could be valuable for a variety of applications.

The retrieval and purification of a macroscopic aged sample of protactinium-231 is described. The 231 Pa was separated from its decay daughters using a precipitation based method. The method exploits the hydrolytic behavior and insolubility of protactinium rather than attempting to avoid it by way of concentrated hydrofluoric and sulfuric acids, which have been shown to vitiate separations using ion-exchange and solvent extraction based methods. Based on alpha spectrometry the source was previously separated in 1959–1960, consistent with the Harwell Pa separations program. The method described here achieved 98% recovery of the 231 Pa with a final alpha-radiopurity of 93.75% in contrast to the 20.25% radiopurity of the starting material.

High Purity Germanium (HPGe) detector gamma-ray spectrometry with 500 cc Marinelli beaker geometry was used for radioactivity measurement in some specific areas of Kingdom of Saudi Arabia (KSA). The detection limits of 210 Pb, 238 U, 226 Ra, 232 Th and 40 K in soil, fertilizers, and vegetables lie mostly below 1 Bq/kg. The activity concentrations of 238 U and 226 Ra in local phosphate fertilizers were measured in the range of 236.8–879.0 Bq/kg and 101.5–297.0 Bq/kg, respectively. The respective activity concentrations of 238 U and 226 Ra measured in one charge of German phosphate fertilizer are in the range of 552.7–790.0 Bq/kg and 280.6–317.0 Bq/kg. The activity concentrations of 232 Th are assessed to have maximum values up to 2.24 Bq/kg in locally manufactured phosphate fertilizers. Local urea exhibited concentration level (Bq/kg) of 210 Pb, 238 U, 226 Ra, 232 Th and 40 K below the detection limit. Mean values of activity concentrations of 238 U in agricultural soil of Wadi Fatima, Taif, Hada Al-Sham, Madina City and Abyar Al-MashiMadina are 21.7 ± 3.24, 38.2 ± 4.1, 17.6 ± 2.1, 34.3 ± 3.5 and 32.7 ± 2.4 Bq/kg, respectively. The respective mean of 226 Ra activity concentrations in those areas are 12.16 ± 1.16, 20.2 ± 1.33, 11.21 ± 0.4, 21.4 ± 1.7 and 21.0 ± 1.22 Bq/kg. The specific activity of 232 Th in the respective areas has been measured as 12.6 ± 1.3, 25.3 ± 0.8, 11.5 ± 0.9, 20.4 ± 2.4 and 20.0 ± 1.2 Bq/kg. Activity concentrations of 210 Pb, 238 U, 226 Ra and 232 Th in the vegetable samples are mostly found in the range of 0.37 Bq/kg to 37.8 Bq/kg. The 40 K specific activity lies in the range of 44.4–196 Bq/kg. The calculated absorbed dose rates in the representative locations are 24.07–53.28 nGy/h.

The work reported in this paper provides a systematic study towards the development of an optimized strategy for preparation of a clinically relevant dose of 90 Y-labeled dimeric RGD peptide derivative, DOTA-E[c(RGDfK)] 2 [DOTA-(RGD) 2 ] for in vivo targeted therapy utilizing 90 Y obtained from a novel electrochemical 90 Sr/ 90 Y generator. The performance of the generator was evaluated to ensure its suitability for providing 90 Y in adequate quantity and purity required for formulation of clinically relevant dose for PRRT. 90 Y-DOTA-(RGD) 2 was synthesized in high yield (86.2 ± 2.5%) and radiochemical purity (98.4 ± 0.5%) using clinically relevant dose (∼3.8 GBq) of 90 Y. In vitro stability studies revealed that the radiolabeled conjugate retained its radiochemical purity in normal saline and human serum. Preliminary biodistribution studies carried out in C57/BL6 mice bearing melanoma tumors showed that the preparation exhibited significant tumor uptake (5.30 ± 0.78% of injected activity at 30 min post-injection) with good tumor to background ratio. The optimized radiolabeling protocol seems to be an attractive strategy which is largely viewed as a springboard to realize scope of developing 90 Y labeled cyclic RGD peptides for targeted therapy of tumors over-expressing integrin- α v β 3 receptors.

A potential dopamine D 4 receptor radioligand, 3-[4-(4-[ 18 F]fluorobenzyl)piperazin-1-ylmethyl]pyrazolo[1,5- a ]pyridine was synthesized through a one-pot two-step procedure with total yield 18.5% (decay corrected). The molar radioactivity was 115 GBq/ μ mol and the radiochemical purity was greater than 95.5%. Its affinity and selectivity for dopamine D 2 -like receptors were measured through in vitro receptor binding experiments and the K i for D 4 receptor was determined to be 17 ± 0.5 nM. The partition coefficient (Log P ) of it was determined to be 2.80 ± 0.10 through octanol experiment. The in vivo biodistribution of it in rat brain exposed that the radioligand penetrates through blood-brain- barrier (BBB) and may specifically bind to dopamine D 4 receptor. The results indicated that the radioligand shows promise for the in vivo study of dopamine D 4 receptor.

The synthesis, characterization and biological evaluation of N-Tolueneferrocenecarboxamide labeled with technetium-99m ( 99m Tc-TTCC) is reported. Biological studies in Wistar rats showed the ability of 99m Tc-TPCC to cross the intact blood-brain barrier. In vivo biodistribution indicated that this complex had good brain uptake (1.32% ID/g at 5 min and 0.64% ID/g at 60 min) and good retention (about 50% of the activity was retained in the brain at 60 min post-injection). Regional brain distribution study showed that hippocampus, where the 5-HT1A receptor density is high, had the highest uptake (0.73% ID/g at 5 min p.i.) and the cerebellum, where the 5-HT1A receptor density is low, had the lowest uptake (0.12% ID/gID/g at 5 min p.i.). After blocking with 8-hydroxy-2-(dipropylamino) tetralin, the uptake of hippocampus was decreased significantly from 0.73% ID/g to 0.20% ID/g at 5 min p.i., while the cerebellum had no significant decrease. This result indicates that 99mTc complex has specific binding to 5-HT1A receptor.

Radioimmunotherapy (RIT) with anti CD20 MoAb conjugated to a β − emitting radioisotope like 131 I or 90 Y has the added advantage of delivering radiation not only to tumor cells that bind the antibody but also due to a crossfire effect, to neighboring tumor cells inaccessible to the antibody. In order to make available an indigenous radioimmunotherapeutic agent for Non Hodgkin's Lymphoma (NHL), radioiodinated Rituximab has been prepared and evaluated at a clinical scale. Radioiodination of Rituximab was performed by the conventional Chloramine T method using 7.4 GBq Na 131 I in a lead shielded plant. Six batches of radioiodination were prepared and characterized by electrophoresis and HPLC to evaluate the reproducibility of the product. The product remained stable retaining the radiochemical purity > 95% upto 5 days after radioiodination. In vitro cell binding studies and biodistribution studies in normal Swiss mice have indicated the potential of this molecule as a radioimmunotherapeutic agent for NHL.