Rapid fabrication and dissolution of pressed ⁵⁸Ni/Mg matrix targets for ⁵⁵Co production

Beyond the use of conventional short-lived PET radionuclides, there is a growing interest in tracking larger biomolecules and exploring radiotheranostic applications. One promising option for imaging medium-sized molecules and peptides is ⁵⁵Co (T₁/₂ = 17.5 h, β⁺ = 76%), which enables imaging of new and already established tracers with blood circulation of several hours. Additionally, ⁵⁵Co can be paired with the Auger-Meitner emitter ^58mCo (T₁/₂ = 9 h, 100% IC) for radiotheranostic applications. Here we report on ⁵⁵Co production via the ⁵⁸Ni(p,α)⁵⁵Co reaction channel using pressed ⁵⁸Ni and Mg matrix targets.

This set up is capable to produce and isolate 240 ± 20 MBq [⁵⁵Co]Co^+ 2 (80% RCY) with 4 ml 0.25 M HEPES at 35 min post End Of Bombardment for 3 h, 25 µA protons irradiation. The RNP of the eluate is 99.98 ± 0.014% as measured 2 h & 17 h post EOB. AMA was determined to 1.5 ± 0.5 GBq/µmol [⁵⁵Co]Co-DOTA at EOB. Mg dissolves rapidly in the acid mixture, leaving behind a porous, sponge-like Ni matrix increasing the surface area of the Ni and therefore accelerating the dissolution.

We present a novel, simple, and rapid method to produce ⁵⁵Co with pressed ⁵⁸Ni/Mg matrix targets enabling faster target fabrication and dissolution. By using a simple hydraulic press, mechanically stable target coins useful for solid target irradiation are fabricated within 5 min and can be dissolved in 10 min at room temperature. The foils remain intact after irradiation and can endure irradiation conditions providing sufficient activity (> 200 MBq) for clinical doses. The method presented here using Mg as a support metal for fixation of the actual target material into target coins is applicable for other target combinations as well. Using Mg as a support metal is suitable due to its thermal conductivity, low activation, minimal impact on purification chemistry, softness, ductility, and rapid dissolution in acid.