Labelling of Granulocytes by Phagocytic Engulfment with (64)Cu-Labelled Chitosan-Coated Magnetic Nanoparticles.

Purpose: The aim of the present work was to perform the labelling of granulocytes by theirengulfment with chitosan-coated magnetic 64Cu nanoparticles (MNPs) in order to obtain aradiopharmaceutical suitable for dual imaging (PET–MRI) of inflammatory/infective diseases.Procedures: Specimens of 5–20 mg MNPs were washed with saline–isotonic solution andrecuperated by magnetic decantation; assessment of the release of 64Cufrom labelled granulocytes in plasma was performed by measuring the radioactivity of both the cellularpellet and the supernatant solution.Results: Our data showed the binding capacity of chitosan-coated MNPs for cationic metal. Theamount of Cu+2 chelated captured per milligram of MNPs was constant and independent of thereagent concentrations. In all cases, more than 90% of the engulfed granulocytes were positiveto the TBE test. The MNPs were localised within the cells.Conclusion: In our in vitro model, MNPs are taken up by granulocytes through phagocytosis,whereas previously described methods were based on the use of a chelating agent that permitCu to cross the cell membrane. Moreover, the 64Cu-engulfed granulocytes showed a highstability of up to 80% of retained radioactivity after 24 h of incubation.; 10 mg MNPs wasallowed to reactwith 16 μg 64Cu [64Ni(p,n) at 12–9 MeV] followed by anion exchange chromatographywith a specific activity of 56 MBq/μg. Pellets of granulocytes were obtained from peripheral blood;MNPs engulfment by granulocytes was obtained and granulocyte-engulfed viability was assessed bythe trypan blue exclusion (TBE) test performed at 5 min, 2 h and 4 h; 15–58 μg Cu2+ (CuCl2·H2O) in 50 μl of acidified (pH 5.5)saline solution was added to the MNPs re-suspended saline–isotonic solution