Copper-64 was produced as a by-product of 55Co via 64Ni(p,n)64Cu by 15 MeV proton bombardment of natNi resulting in a thick target yield of 5.31 MBq/μAh (143.5 μCi/μAh) and a radiochemical separation yield of 95% (radionuclide
purity >97% after 25 hours of bombardment). Rituximab was successively labeled with [64Cu]-CuCl2. N-succinimidyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA-NHS) was prepared at 25 °C using DOTA and
N-hydroxy succinimide (NHS) in CH2Cl2 followed by the addition of 1 ml of a Rituximab pharmaceutical solution. Radiolabeling was performed at 37 °C in 3 hours.
Radio thin-layer chromatography showed an overall radiochemical purity of 90–95% at optimized conditions (specific activity=30
GBq/mg, labeling efficacy; 82%) using various chromatography systems. The final isotonic 64Cu-DOTA-Rituximab complex was passed through a 0.22 μm filter and checked by gel electrophoresis for radiolysis control. Stability
of the final product was checked in the formulation and in presence of human serum at 37 °C.