Nanomaterial-based adsorbents: the prospect of developing new generation radionuclide generators to meet future research and clinical demands

Synthesis of Mesoporous Tetragonal ZrO2, TiO2 and Solid Solutions and Effect of Colloidal Silica on Porosity

Metal oxides possessing a large surface area, pore volume and desirable pore size provide more varieties and active industrial potentials. Nevertheless, it is very challenging to produce crystal metal oxides while keeping satisfactory porosity features, especially for ternary compositions. High temperature is usually needed to produce crystal metal oxides, which readily leads to the collapse of the pore structure. Herein, by employing a 'soft' dispersant agent and a hard silica template, ZrO2, TiO2 and Zr-Ti solid solutions having a tetragonal crystal structure are produced and the silica-leached materials are characterized from macroscopic to atomistic scales. The micron-sized particulate powders are composed of nanoscale 'building blocks', with crystallite sizes between ~8 and 21 nm. These polycrystalline ceramic powders exhibit a high specific surface area (up to ~200 m2·g-1) and pore volume (up to 0.5 cm3·g-1), with a pore size range of ~5-20 nm. Importantly, the Zr/Ti-O-Si-OH chemical bonds exist on the particle surface, with about two-thirds of the surface covered by silica. The hydroxyl groups can further post-graft organic ligands or directly associate with species. Synthesized mesoporous metal oxides are highly homogenous and could potentially be used in various applications because of their tetragonal structure and porosity features.

Synthesis of pH responsive malononitrile functionalized metal organic framework MIL-100(Fe) for efficient adsorption of uranium U(VI) from real-life alkaline leach liquor

The porous framework of MIL-100(Fe) was functionalized using malononitrile (MN), through an in-situ Knoevenagel condensation reaction to introduce abundant -CN groups on the surface of the developed adsorbent. The resultant MN-functionalized MIL-100(Fe) exhibited excellent Uranium (U(VI)) removal capacity (i.e., 270 mg/g) at highly alkaline pH (⁓ 10). Different coexisting cations and anions show negligible influence on the U-removal and it was 92.1-99.7 % in presence of different co-ions, with the concentration from 10 to 50 mg/L. Moreover, MIL-100(Fe)_MN showed extremely selective U removal from the actual alkaline leach liquor (⁓ 97 %), without any pH adjustment and leaching of the constituent Fe. The surface-grafted -CN groups were predominantly active towards the coordinative interactions with the U(VI) ionic moieties, as evident from the XPS and FTIR analysis. The MIL-100(Fe)_MN adsorbent was also subjected to five consecutive adsorption-desorption cycles, with >90 % U removal after 5th cycle. Moreover, the regenerated MIL-100(Fe)_MN was structurally and functionally resilient, as observed from the morphological and crystallographic analysis. A convection-pore diffusion based transport model was used to analyze the optimized mass transfer parameters. Overall, the present study highlights the simple design and development of malononitrile-functionalized MIL-100(Fe) as an efficient and selective adsorbent for U(VI) removal from U-rich alkaline leach liquor.

Preclinical PET Imaging of Tumor Cell Death following Therapy Using Gallium-68-Labeled C2Am

There is an unmet clinical need for imaging agents capable of detecting early evidence of tumor cell death, since the timing, extent, and distribution of cell death in tumors following treatment can give an indication of treatment outcome. We describe here 68Ga-labeled C2Am, which is a phosphatidylserine-binding protein, for imaging tumor cell death in vivo using positron emission tomography (PET). A one-pot synthesis of 68Ga-C2Am (20 min, 25 °C, >95% radiochemical purity) has been developed, using a NODAGA-maleimide chelator. The binding of 68Ga-C2Am to apoptotic and necrotic tumor cells was assessed in vitro using human breast and colorectal cancer cell lines, and in vivo, using dynamic PET measurements in mice implanted subcutaneously with the colorectal tumor cells and treated with a TRAIL-R2 agonist. 68Ga-C2Am showed predominantly renal clearance and low retention in the liver, spleen, small intestine, and bone and generated a tumor-to-muscle (T/m) ratio of 2.3 ± 0.4, at 2 h post probe administration and at 24 h following treatment. 68Ga-C2Am has the potential to be used in the clinic as a PET tracer for assessing early treatment response in tumors.

Green synthesis of alumina nanoparticle using Hibiscus rosa-sinensis leaf extract as a candidate for molybdenum-99 adsorbent

Al₂O₃ nanoparticle is effectively used as an adsorbent for the low specific activity of molybdenum-99 (⁹⁹Mo). The Al₂O₃ nanoparticle was synthesized by the green synthesis method using Hibiscus rosa-sinensis leaf extract (HRE). The Al₂O₃ nanoparticle synthesized using 10% of the HRE has a crystallite size of 4.9 nm, a surface area of 254.6 m²/g, a pore size of 9.1 nm, a pore volume of 0.58 cm³/g and has a Mo adsorption capacity of 43.4 ± 6.1 mg Mo/g.

Surface modification of acid-functionalized mesoporous gamma-alumina for non-fission 99Mo/99mTc generator

Mesoporous gamma-alumina (MGA) was synthesized for neutron-activated ⁹⁹Mo adsorbent. Acid functionalization of the MGA was carried out to enhance the Mo adsorption capacity and the ⁹⁹Mo breakthrough profile. The acid-treated MGA has a more positive particle charge, rougher surface, smaller particle and pore size, larger surface area, and wider pore distance. The acid-treated MGA has a Mo adsorption capacity of 82.8 ± 6.3 mg Mo/g and resulted in ^99mTc eluate with the ⁹⁹Mo breakthrough at the acceptable level.

Matrices and Affinity Ligands for Antibody Purification and Corresponding Applications in Radiotherapy

Antibodies have become an important class of biological products in cancer treatments such as radiotherapy. The growing therapeutic applications have driven a demand for high-purity antibodies. Affinity chromatography with a high affinity and specificity has always been utilized to separate antibodies from complex mixtures. Quality chromatographic components (matrices and affinity ligands) have either been found or generated to increase the purity and yield of antibodies. More importantly, some matrices (mainly particles) and affinity ligands (including design protocols) for antibody purification can act as radiosensitizers or carriers for therapeutic radionuclides (or for radiosensitizers) either directly or indirectly to improve the therapeutic efficiency of radiotherapy. This paper provides a brief overview on the matrices and ligands used in affinity chromatography that are involved in antibody purification and emphasizes their applications in radiotherapy to enrich potential approaches for improving the efficacy of radiotherapy.

Coal fly ash driven zeolites for the adsorptive removal of the ceftazidime drug

The overall cost and efficiency of an adsorbent material is a major issue in deriving a sorbent into commercial markets. In this study, efforts have been directed to produce adsorption-capable zeolites from the dispensable product of coal power plants, i.e., coal fly ash (CFA). In addition, coal mining water (CW) was used as a direct hydrothermal solvent. The mine water from China's coal mines was used in this experiment to substitute tap water (TP) for synthesizing zeolite from C-type fly ashes with different crystallization temperatures (45 to 95 °C). Here, CW led to the formation of X-type and A-type zeolites of comparable size. Regarding the proper utilization of waste products, i.e., coal fly ash and mine water, the study paves a simple yet extremely cost-effective approach to synthesize workable zeolitic materials for adsorption purposes. The detailed characterization justified the use of CW as a better solvent than TP to prepare zeolites based on their better granular size and fewer carbon impurities. The prepared zeolites were later used as an adsorbent for the trace removal of ceftazidime (CAZ), taken as a model pharmaceutical pollutant. The zeolites prepared using CW realised a higher adsorption capacity of 80 mg g⁻¹ during 20 min of agitation time. The pH, concentration, and external salt effects were also studied to achieve maximum removal efficiency. In general, the proposed approach enables the production of affordable yet efficient zeolite-based adsorbent materials without consuming any toxic and expensive reagents for practical application in environmental remediations.

Diagram showing a systematic approach to preparing zeolites using the hydrothermal approach with the coal mine water and tap water as dissolution solvents.

Therapeutic radionuclides in nuclear medicine: current and future prospects

The potential use of radionuclides in therapy has been recognized for many decades. A number of radionuclides, such as iodine-131 ((131)I), phosphorous-32 ((32)P), strontium-90 ((90)Sr), and yttrium-90 ((90)Y), have been used successfully for the treatment of many benign and malignant disorders. Recently, the rapid growth of this branch of nuclear medicine has been stimulated by the introduction of a number of new radionuclides and radiopharmaceuticals for the treatment of metastatic bone pain and neuroendocrine and other malignant or non-malignant tumours. Today, the field of radionuclide therapy is enjoying an exciting phase and is poised for greater growth and development in the coming years. For example, in Asia, the high prevalence of thyroid and liver diseases has prompted many novel developments and clinical trials using targeted radionuclide therapy. This paper reviews the characteristics and clinical applications of the commonly available therapeutic radionuclides, as well as the problems and issues involved in translating novel radionuclides into clinical therapies.

An overview of radioisotope separation technologies for development of 188W/188Re radionuclide generators providing 188Re to meet future research and clinical demands

Separation technologies for ¹⁸⁸W/¹⁸⁸Re radionuclide generators.