Preparation of 99Mo/99mTc generator based on alumina 99Mo-molybdate (VI) gel

Experimental study for the decontamination of various surfaces from 99Mo using PVA/Borax/Al(OH)3 strippable hydrogel

Polyvinyl alcohol (PVA) is a beneficial polymer capable of forming hydrogels helpful in a wide range of applications. Hydrogels based on cross-linking of PVA with borax, and able to incorporate with a decontaminating agent have been used in the decontamination of 99Mo from contaminated surfaces. Aluminum hydroxide has been introduced in the formulations of PVA-borax, to increase the gel efficiency for 99Mo decontamination from surfaces. The formulations were investigated with glass, stainless steel, and wood as examples of different surfaces. When the hydrogel is sprayed on different surfaces, it forms rapidly and adheres well. Moreover, the hydrogel was shown to efficiently decontaminate surfaces contaminated with 99Mo by a maximum value of decontamination factor (D.F) for glass, stainless steel, and wood to be 43.5, 31.3, and 19.6 respectively.

Noninvasive Imaging of Tumor PD-L1 Expression Using [99mTc]Tc-Labeled KN035 with SPECT/CT

Programmed cell death protein-1/ligand-1 (PD-1/PD-L1) checkpoint blockade is a major breakthrough in cancer therapy, but identifying patients likely to benefit from this therapy remains challenging. Immunohistochemistry is not informative about PD-L1 expression heterogeneity because of the limitations of invasive tissue collection. Noninvasive SPECT imaging is an approach to patient selection and therapeutic monitoring by assessing the PD-L1 status throughout the whole body. Here, we radiolabeled a single-domain PD-L1 antibody with technetium-99m (^99mTc) for immune-SPECT imaging to evaluate its feasibility of detecting PD-L1 expression. The radiochemical purity of [^99mTc]Tc-HYNIC-KN035 was 99.40 ± 0.11% with a specific activity of 2.68 MBq/μg. [^99mTc]Tc-HYNIC-KN035 displayed a high PD-L1 specificity both in vitro and in vivo and showed a high specific affinity for PD-L1 with an equilibrium dissociation constant (K_D) of 31.04 nM. The binding of [^99mTc]Tc-HYNIC-KN035 to H1975 cells (high expression of PD-L1) was much higher than to A549 cells (low expression of PD-L1). SPECT/CT imaging showed that H1975 tumors were visualized at 4 h post-injection and became clearer with time. However, mild tumor uptake was observed in A549 tumors and H1975 tumors of the blocking group at all time points. The uptake value of [^99mTc]Tc-HYNIC-KN035 in H1975 tumors was increased continuously from 9.68 ± 0.91% ID/g at 4 h to 13.31 ± 2.23% ID/g at 24 h post-injection, which was higher than in A549 tumors with %ID/g of 4.59 ± 0.76 and 5.54 ± 0.28 at 4 and 24 h post-injection, respectively. These specific bindings were confirmed by blocking studies. [^99mTc]Tc-HYNIC-KN035 can be synthesized easily and specifically targeted to PD-L1 in the tumor environment, allowing PD-L1 expression assessment noninvasively and dynamically with SPECT/CT imaging.

The application of atomic layer deposition in the production of sorbents for 99Mo/99mTc generator

New production routes for ⁹⁹Mo are steadily gaining importance. However, the obtained specific activity is much lower than currently produced by the fission of U-235. To be able to supply hospitals with ⁹⁹Mo/^99mTc generators with the desired activity, the adsorption capacity of the column material should be increased. In this paper we have investigated whether the gas phase coating technique Atomic Layer Deposition (ALD), which can deposit ultra-thin layers on high surface area materials, can be used to attain materials with high adsorption capacity for ⁹⁹Mo. For this purpose, ALD was applied on a silica-core sorbent material to coat it with a thin layer of alumina. This sorbent material shows to have a maximum adsorption capacity of 120 mg/g and has a^99mTc elution efficiency of 55 ± 2% based on 3 executive elutions.

99Mo/99mTc radioisotope generator based on adsorption of 99Mo (VI) on cerium (IV) molybdate column matrix

Based on neutron activated 99Mo, a procedure for preparation of 99Mo/99mTc radioisotope generator was developed. Batch equilibration method was used to investigate the sorption behavior of Mo (VI) (10−4 M) in chloride and nitrate solutions on cerium (IV) molybdate gel matrix using 99Mo radiotracer. The breakthrough sorption capacity of cerium molybdate gel matrix for 99Mo (VI) (3×10−2 M) were found to be 0.54 mmol/g of the sorbent [1 g column (0.6 cm i.d.)]. Elution performance of the generated 99mTc from cerium molybdate-99Mo chromatographic column was investigated as a function of inside diameter of the column, amount of the bed matrix and flow rate of the eluent. Based on the obtained results, 99Mo/99mTc radioisotope generator was prepared based on adsorption of neutron activated 99Mo (VI) of low specific activity onto chromatographic columns packed with 5 g cerium molybdate gel matrix. The radioactivity of 99mTc is periodically eluted with 10 mL 0.9% NaCl solution at a flow rate of 1 mL/min. Elution yield of 78±5% was obtained with high chemical, radionuclidic (99Mo breakthrough 1×10−3±0.3×10−3%) and radiochemical purity (97±2%).

Preparation and characterization of iron(III) 99Mo-molybdate(VI) gels for the assessment of 99mTc elution performance

New iron(III) 99Mo-molybdate(VI) gels (Fe99Mo) of high Mo content were prepared by the precipitation/filtration method. 99Mo–MoO3 dissolved in NaOH was added to aqueous solutions of Fe(NO3)3 at Mo/Fe mole fractions ~2.21 and 1.99 with continuous stirring at ambient room temperature. Two different Fe99Mo were precipitated from the mixed solutions adjusted at pH 2 and 4.7. The amount of water of hydration increased with the increasing the gel settling time and pH of the mixed solution. The matrices were characterized by radiometric, XRD, SEM, XRF, FT-IR, TGA, and DTA measurements. Small chromatographic columns of 2.0 g Fe99Mo containing ≥800 mg Mo tagged with 740 MBq 99Mo were eluted with 5 mL saline solution. Highly reproducible 99mTc elution indices suitable for preparation of 99Mo/99mTc generators were achieved from generator supported with 0.5 g Al2O3 filter. Elution performance of 99mTc radionuclide was highly dependent on the gel structural properties.

Studies on 99Mo–99mTc adsorption and elution behaviors using the inorganic sorbent ceric tungstate and conventional organic resins

Adsorption behavior of 99Mo(VI) and 99mTc(VII) was studied on ceric tungstate (CeW) and compared with the adsorption on the conventional cation and anion exchangers Dowex-50X8 and AG-2X8, respectively. The studies were carried out under static and dynamic conditions. The effect of contact time and pH on the adsorption was investigated under static conditions. High Kd-values for sorption of 99Mo(VI) on (CeW) were obtained over the investigated pH range. 99mTc was adsorbed with much lower Kd-values. The Kd-values were pH dependent. Kd-values of 99Mo-adsorption on AG-2X8 were lower than those on (CeW) and vice versa for 99mTc. Ionic species of both elements were not adsorbed on Dowex-50X8, indicating the absence of cationic species and the adsorption of both elements on AG-2X8 and (CeW) as anionic species. The loading and elution behaviors of 99Mo and 99mTc on (CeW) were studied using different eluents. 99Mo remained strongly adsorbed under all conditions whereas 99mTc was easily eluted. Adsorption of some fission products, i.e. 95Zr(IV) and 95Nb(V), in addition to 123mTe(IV) and 75Se(IV), as representatives of their corresponding fission product isotopes, as well as 181Hf, as probable radioactive contaminant was also studied. Solutions of the ionic species of those metals were loaded in mixtures together with 99Mo on (CeW) columns. Strong adsorption of those ionic species and 99Mo on (CeW) was found whereas 99mTc was easily eluted. Different eluents were investigated for eluting 99mTc from 99Mo-adsorbed on (CeW).