Mesoporous Alumina (MA) Based Double Column Approach for Development of a Clinical Scale ⁹⁹Mo/^99mTc Generator Using (n,γ)⁹⁹Mo: An Enticing Application of Nanomaterial

This paper describes the utility of mesoporous alumina (MA), a high capacity nanomaterial based sorbent, for the development of a clinical grade ⁹⁹Mo/^99mTc generator using (n,γ)⁹⁹Mo. Synthesis of MA was performed using a glucose template in an aqueous system. Structural characterization of the nanosorbent was carried out by analytical techniques such as X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), scanning electron miscroscopy (SEM), transmission electron microscopy (TEM), thermogravimetry-differential thermal analysis (TG-DTA), Fourier transform infrared (FTIR) spectroscopy, and Brunauer–Emmett–Teller (BET) surface area analysis. The material synthesized was mesoporous and nanocrystalline, with average crystallite size of 2–3 nm with a large surface area of 230 ± 10 m² g^–1. In order to evaluate the surface charge of MA in aqueous solution, the zeta potential was determined at different pH environments. Adsorption characteristics of the sorbent such as time course of the adsorption, distribution ratios of ⁹⁹Mo and ^99mTc ions, Mo sorption capacity under static and dynamic conditions, ⁹⁹Mo adsorption pattern and ^99mTc elution pattern were determined to assess its effectiveness in the preparation of ⁹⁹Mo/^99mTc generator. The measured distribution ratio values indicate that ⁹⁹Mo is both strongly and selectively retained by MA at acidic pH and ^99mTc could be readily eluted from it, using 0.9% NaCl solution. The static sorption capacity and practical sorption capacity under dynamic conditions of MA was determined to be 225 ± 20 and 168 ± 12 mg Mo per gram of sorbent, respectively. With a view to realize the scope of developing clinical scale generator, a novel tandem column generator concept was used in which two ⁹⁹Mo loaded columns were connected in series. In this method ^99mTc eluted from the first column was fed to the second column to achieve higher radioactive concentration (RAC) as well as purity of ^99mTc. A 26 GBq (700 mCi) ⁹⁹Mo/^99mTc generator was developed using (n,γ)⁹⁹Mo having specific activity of ∼18.5 GBq (500 mCi)/g of Mo. The ^99mTc eluted from the generator possessed high radionuclidic, radiochemical, and chemical purity and was amenable for the preparation of ^99mTc-labeled radiopharmaceuticals. The technology can be adapted by those countries having research reactors with flux >1 × 10¹⁴ n·cm^–2·s^–1 to produce ⁹⁹Mo by (n,γ) route. The capacity of the generator can be scaled up to 260 GBq (7 Ci) using (n,γ)⁹⁹Mo produced from a reactor with flux >1 × 10¹⁵ n·cm^–2·s^–1