Journal of Isotopes (Aug 2022)
The Glioma Model micro-PET Imaging and Biodistribution of 68Ga Labeled Fibroblast Activation Protein Inhibitor
Abstract
To investigate the biodistribution and micro-PET imaging of 68Ga labeled fibroblast activation protein inhibitor (68Ga-FAPI-04) in normal mice and glioma nude mice, 68Ga-FAPI-04 was synthesized using DOTA-modified fibroblast activation protein inhibitor as precursor. The synthesis yield, radiochemical purity and in vitro stability were analyzed by radio-HPLC, and the hydrophilicity of 68Ga-FAPI-04 was evaluated by lipo-hydro partition coefficient. Twenty ICR mice were randomly divided into 5 groups. 3.7 MBq of 68Ga-FAPI-04 was injected by tail vein per mouse, then the mice were killed at 5, 15, 30, 60, 120 min post-injection(pi.). The main organs and tissues were collected and weighed, then the radioactivity was measured, and the uptake of each tissue or organ was calculated. The nude mice bearing U87MG glioma model were established, then the biodistribution study and micro-PET imaging were performed. The results indicate that the synthesis yield of 68Ga-FAPI-04 was (97.38±1.32)% (n=3), the radiochemical purity was 100%，and the in vitro stability and hydrophilicity were good. The biodistribution study of normal-ICR mice showed that 68Ga-FAPI-04 was cleared from blood rapidly and mainly excreted from kidneys, and the radioactivity uptake in brain was low. The biodistribution and micro-PET of U87MG tumor-bearing nude mice showed high radioactivity at the tumor targets. The uptake of 68Ga-FAPI-04 at the tumor targets reached (2.50±0.00)%ID/g at 90 min pi. The tumor-to-background ratios (TBRs) were（6.26±0.09）, （5.06±0.02）, （5.54±1.47） and （5.51±0.03） at 30, 60, 90 and 120 min pi., respectively. The preliminary studies indicate that 68Ga-FAPI-04 is synthesized easily with high yields, and is stable in vitro. The radiotracer was mainly excreted from kidneys, and targeting tumor targets with clear images in micro-PET of glioma models. Therefore, 68Ga-FAPI-04 might be a potential brain tumor imaging agent.
