Selected Ga-68-siderophores versus Ga-68-colloid and Ga-68-citrate: biodistribution and small animal imaging in mice

Background. Ga-68-triacetylfusarinine C (TAFC) and Ga-68-ferrioxamine E (FOXE) show great potential to be used as highly sensitive and selective tracers for Aspergillus infection imaging. Here we report on a comparison of the ex vivo biodistribution and small animal imaging of Ga-68-TAFC and Ga-68-FOXE versus Ga-68-colloid and Ga-68-citrate as unspecific control in mice. Methods. The radiochemical purity of tested Ga-68 labelled tracers was determined by RP-HPLC or ITLC-SG. Ex vivo biodistribution was studied in normal DBA/2 mice 30 min and 90 min p.i. Static and dynamic imaging were performed using mu PET/CT. Results. Ga-68-TAFC and Ga-68-FOXE showed rapid renal excretion and low blood values even 90 min p.i. Ga-68-TAFC showed almost no retention in other organs while 68Ga-FOXE displayed some uptake in gastrointestinal tract. Ga-68-colloid and Ga-68-citrate revealed significantly different ex vivo biodistribution. Ga-68-colloid showed pronounced radioactivity retention in the liver, while Ga-68-citrate displayed high blood values and significant retention of radioactivity in highly perfused organs. Conclusions. From the results, both Ga-68-TAFC and Ga-68-FOXE have excellent and significantly different in vivo behaviour compared to Ga-68-colloid and Ga-68-citrate. Ga-68-TAFC in particular confirmed its great potential use as a specific tracer for Aspergillus infection imaging.