(426e) Cu-Selective Membrane Adsorbers for Medical Isotope Production

Radiopharmaceuticals offer promising new approaches for imaging and treatment for cancer patients; however, the current supply of these novel drugs is too low to support clinical trials. Copper-67 (Cu-67), can provide treatment (via beta decay) and imaging (via gamma rays). Cu-67 is purified using resin-packed columns, which are known to suffer from diffusion-limited transport. The practical implications of these limitations are (1) low column flow rates, (2) high elution volumes and (3) long purification times—all of which contribute to the bottleneck in the sustained supply of Cu-67. Due to the short half-life (2.58 days) of Cu-67, rapid purification is key for increasing the availability of the isotope for clinic trials and use.

A promising alternative to resin-packed columns are membrane adsorbers, which have seen recent success in the purification of biologics. This contribution describes our efforts to graft glycidyl methacrylate (GMA) from polyvinylidene fluoride (PVDF) membranes through activator generated by electron transfer, a type of, atom transfer radical polymerization (AGET ATRP). After grafting poly(GMA), diamine ligands of varying chain length (putrescine and ethylene diamine) are attached to the brushes through an epoxide ring opening reaction. Membranes are characterized by attenuated total reflection Fourier-Transform infrared spectroscopy throughout the synthesis process (grafting and ring-opening) to support functionalization. Membrane permeability was calculated from pure-water flux experiments in a dead-end filtration cell to be 5166 LMH/bar for unmodified PVDF membranes, 4692-648 LMH/bar for GMA modified membranes, and 4124-175 LMH/bar for the amine functionalized GMA membranes. Membrane morphology and surface chemistry was examined using electron microscopy (SEM) and SEM x-ray photoelectron spectroscopy (XPS). XPS analysis confirms that the Cu catalyst was successfully washed from the membrane after AGET ATRP. Batch adsorption experiments were conducted for Cu and competitor ions (Ni, Zn) in pH 2 HCl solutions. Ion concentrations were measured using an inductively-coupled plasma optical emission spectrophotometer (ICP-OES) and the binding capacity was calculated by modeling equilibrium adsorption data with the Langmuir isotherm. The results of this research are laying the groundwork for implementing membrane absorbers as a new separation material for medical isotope purification.