Effects of High Gamma Doses on the Structural Stability of Metal-Organic Frameworks.

Four different MOFs were exposed to γ rays by a cobalt-60 source reaching a maximum dose of 5 MGy. The results showed that the MIL-100 (Cr) and MIL-100 (Fe) did not exhibit obvious structural damage, suggesting their excellent radiation stability. MIL-101 (Cr) showed good radiation stability up to 4 MGy, but its structure started degrading with increasing radiation dose. Furthermore, the results showed that the structure of AlFu MOFs started to decompose at a gamma dose of 1 MGy, exhibiting a much lower tolerance to γ radiation. At this radiation energy, the dominant interaction of the gamma-ray with MOFs is the Compton effect and the radiation stability of MOFs can be improved by prolific aromatic linkers, high linker connectivity, and good crystallinity. The results of this study indicate that MIL-100 and MIL-101 MOFs have a good potential to be employed in nuclear applications, where relatively high radiation doses play a role, for example, nuclear waste treatment and radionuclides production.

Modelling of the 177mLu/177Lu radionuclide generator.

In order to determine the potential of 177mLu/177Lu radionuclide generator in 177Lu production it is important to establish the technical needs that can lead to a clinically acceptable 177Lu product quality. In this work, a model that includes all the processes and the parameters affecting the performance of the 177mLu/177Lu radionuclide generator has been developed. The model has been based on the use of a ligand to complex 177mLu ions, followed by the separation of the freed 177Lu ions. The dissociation kinetics of the Lu-ligand complex has been found to be the most crucial aspect governing the specific activity and 177mLu content of the produced 177Lu. The dissociation rate constants lower than 1*10-11 s-1 would be required to lead to onsite 177Lu production with specific activity close to theoretical maximum of 4.1 TBq 177Lu/mg Lu and with 177mLu content of less than 0.01%. Lastly, the calculations suggest that more than one patient dose per week can be supplied for a period of up to 7 months on starting with the 177mLu produced using 3 g Lu2O3 target with 60% 176Lu enrichment. The requirements of the starting 177mLu activity production needs to be adapted depending on the required patient doses, and the technical specifications of the involved 177mLu-177Lu separation process.

Solid phase extraction-based separation of the nuclear isomers 177mLu and 177Lu.

A solid phase extraction based 177mLu-177Lu separation method has been investigated for its feasibility to be used in the radionuclide generator. The use of 2,2',2"-(10-(2,6-dioxotetrahydro-2H-pyran-3-yl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid, (DOTAGA-anhydride) allowed grafting of DOTA (1,4,7,10-tetraazacyclododecane N,N',N″,N‴-tetraacetic acid) complex on the surface of commercially available amino propyl silica. The grafting of DOTA has been confirmed by several characterization techniques. The thermogravimetric analysis reveals that the 0.33 mmol DOTA groups have been grafted per gram of silica. However, during the Lu ion complexation, a 10 times lower Lu adsorption capacity of 0.03 mmol g-1 could be achieved under the studied reaction conditions. The results indicate that the grafting of DOTA on solid affects the Lu coordination and also influences the kinetics of Lu-DOTA complexation. The weak coordination resulted in high 177mLu leakage, while the unreacted DOTA groups interfer with the 177Lu release. This is evident from the 0.3% 177mLu leakage combined with a177Lu extraction efficiency of 25%. Overall, the results show a177mLu-177Lu separation with a maximum 177Lu/177mLu activity ratio of 25. But this is still far away from clinically acceptable activity ratio of 10,000 for which future work is recommended.

Large-scale production of lutetium-177m for the 177mLu/177Lu radionuclide generator.

In this work, 177mLu has been produced by irradiation of natural Lu2O3 targets at the BR2 reactor (Mol, Belgium) and the obtained data together with literature values have been used to theoretically investigate the production of 177mLu at different neutron fluxes, irradiation times and enrichment of 176Lu. The irradiation time (tmax) needed to reach the maximum 177mLu production has been found to change from 42, 12, 4 days with the increase in the thermal neutron flux from 2*1014, 8*1014, 2.5*1015 n cm-2 s-1, respectively while keeping the maximum 177mLu activity unaffected. The results of our calculations suggest that 0.11 TBq 177mLu with a specific activity of 0.3 TBq g-1 Lu can be produced in a short irradiation time of 4 days using 1g of 84.44% 176Lu enriched Lu2O3 and a thermal neutron flux of 2.5*1015 n cm-2 s-1.

Radionuclide generator-based production of therapeutic 177Lu from its long-lived isomer 177mLu.

BACKGROUND: In this work, a lutetium-177 (177Lu) production method based on the separation of nuclear isomers, 177mLu & 177Lu, is reported. The 177mLu-177Lu separation is performed by combining the use of DOTA & DOTA-labelled peptide (DOTATATE) and liquid-liquid extraction. METHODS: The 177mLu cations were complexed with DOTA & DOTATATE and kept at 77 K for periods of time to allow 177Lu production. The freed 177Lu ions produced via internal conversion of 177mLu were then extracted in dihexyl ether using 0.01 M di-(2-ethylhexyl) phosphoric acid (DEHPA) at room temperature. The liquid-liquid extractions were performed periodically for a period up to 35 days. RESULTS: A maximum 177Lu/177mLu activity ratio of 3500 ± 500 was achieved with [177mLu]Lu-DOTA complex, in comparison to 177Lu/177mLu activity ratios of 1086 ± 40 realized using [177mLu]Lu-DOTATATE complex. The 177Lu-177mLu separation was found to be affected by the molar ratio of lutetium and DOTA. A 177Lu/177mLu activity ratio up to 3500 ± 500 was achieved with excess DOTA in comparison to 177Lu/177mLu activity ratio 1500 ± 600 obtained when lutetium and DOTA were present in molar ratio of 1:1. Further, the 177Lu ion extraction efficiency, decreases from 95 ± 4% to 58 ± 2% in the presence of excess DOTA. CONCLUSION: The reported method resulted in a 177Lu/ 177mLu activity ratio up to 3500 after the separation. This ratio is close to the lower end of 177Lu/177mLu activity ratios, attained currently during the direct route 177Lu production for clinical applications (i.e. 4000-10,000). This study forms the basis for further extending the liquid-liquid extraction based 177mLu-177Lu separation in order to lead to a commercial 177mLu/177Lu radionuclide generator.

Towards the production of carrier-free 99Mo by neutron activation of 98Mo in molybdenum hexacarbonyl -Szilard-Chalmers enrichment.

The neutron irradiation of molybdenum hexacarbonyl has been systematically studied to identify possible improvements for the production of molybdenum-99. After irradiation, the targets were dissolved in dichloromethane, and Szilard-Chalmers liquid-liquid extraction was carried out with aqueous extractants. The effects of the irradiation time, the aqueous phase composition and the irradiated mass were studied with a focus on the chemistry involved. Stable extraction yields of 20% were obtained with enrichment decreasing with target decomposition. Improved enrichment requires decreased decomposition.

Nanocarrier-Mediated Photochemotherapy and Photoradiotherapy.

Photothermal therapy (PTT) and photodynamic therapy (PDT) both utilize light to induce a therapeutic effect. These therapies are rapidly gaining importance due to the noninvasiveness of light and the limited adverse effect associated with these treatments. However, most preclinical studies show that complete elimination of tumors is rarely observed. Combining PDT and PTT with chemotherapy or radiotherapy can improve the therapeutic outcome and simultaneously decrease side effects of these conventional treatments. Nanocarriers can help to facilitate such a combined treatment. Here, the most recent advancements in the field of photochemotherapy and photoradiotherapy, in which nanocarriers are employed, are reviewed.

Experimental Evidence of Negative Linear Compressibility in the MIL-53 Metal-Organic Framework Family.

We report a series of powder X-ray diffraction experiments performed on the soft porous crystals MIL-53(Al) and NH2-MIL-53(Al) in a diamond anvil cell under different pressurization media. Systematic refinements of the obtained powder patterns demonstrate that these materials expand along a specific direction while undergoing total volume reduction under an increase in hydrostatic pressure. The results confirm for the first time the Negative Linear Compressibility behaviour of this family of materials recently predicted from quantum chemical calculations.

Selective gas and vapor sorption and magnetic sensing by an isoreticular mixed-metal-organic framework.

A novel isoreticular oxamato-based manganese(II)-copper(II) open metal-organic framework H(2)O@iso1 featuring a pillared square/octagonal layer structure with alternating open and closed octagonal pores has been rationally prepared. The open-framework topology is responsible for a large selectivity in the separation of small gas (CO(2) over CH(4)) and vapor molecules (CH(3)OH over CH(3)CN and CH(3)CH(2)OH). H(2)O@iso1 displays a long-range three-dimensional ferromagnetic ordering with a drastic variation of the critical temperature as a function of the guest molecule [T(C) < 2.0 K (CO(2)@iso1 and CH(4)@iso1) and T(C) = 6.5 (CH(3)OH@iso1) and 21.0 K (H(2)O@iso1)].

Interplay of metal node and amine functionality in NH2-MIL-53: modulating breathing behavior through intra-framework interactions.

A series of amino-functionalized MIL-53 with different metals as nodes has been synthesized. By determining adsorption properties and spectroscopic characterization, we unequivocally show that the interaction between the amines of the organic linker and bridging µ(2)-OH of the inorganic scaffold modulates metal organic framework (MOF) flexibility. The strength of the interaction has been found to correlate with the electropositivity of the metal.

NH2-MIL-53(Al): a high-contrast reversible solid-state nonlinear optical switch.

The metal-organic framework NH(2)-MIL-53(Al) is the first solid-state material displaying nonlinear optical switching due to a conformational change upon breathing. A switching contrast of at least 38 was observed. This transition originates in the restrained linker mobility in the very narrow pore configuration.

Adsorption and separation of light gases on an amino-functionalized metal-organic framework: an adsorption and in situ XRD study.

The NH(2)-MIL-53(Al) metal-organic framework was studied for its use in the separation of CO(2) from CH(4), H(2), N(2)C(2)H(6) and C(3)H(8) mixtures. Isotherms of methane, ethane, propane, hydrogen, nitrogen, and CO(2) were measured. The atypical shape of these isotherms is attributed to the breathing properties of the material, in which a transition from a very narrow pore form to a narrow pore form and from a narrow pore form to a large pore form occurs, depending on the total pressure and the nature of the adsorbate, as demonstrated by in situ XRD patterns measured during adsorption. Apart from CO(2), all tested gases interacted weakly with the adsorbent. As a result, they are excluded from adsorption in the narrow pore form of the material at low pressure. CO(2) interacted much more strongly and was adsorbed in significant amounts at low pressure. This gives the material excellent properties to separate CO(2) from other gases. The separation of CO(2) from methane, nitrogen, hydrogen, or a combination of these gases has been demonstrated by breakthrough experiments using pellets of NH(2)-MIL-53(Al). The effect of total pressure (1-30 bar), gas composition, temperature (303-403 K) and contact time has been examined. In all cases, CO(2) was selectively adsorbed, whereas methane, nitrogen, and hydrogen nearly did not adsorb at all. Regeneration of the adsorbent by thermal treatment, inert purge gas stripping, and pressure swing has been demonstrated. The NH(2)-MIL-53(Al) pellets retained their selectivity and capacity for more than two years.

Functionalized flexible MOFs as fillers in mixed matrix membranes for highly selective separation of CO2 from CH4 at elevated pressures.

Mixed matrix membranes (MMMs) composed of a glassy polymer (polysulfone) and the flexible metal organic framework NH(2)-MIL-53(Al) exhibit excellent separation properties. In contrast to most reported membranes, CO(2)/CH(4) separation selectivity increases with pressure, related to the flexibility of the filler.