To prepare specific molecular probe ¹⁸F-AlF-1, 4, 7-triazacylononane-1, 4, 7-triacetic acid-(polyethylene glycol)₄-ZD2 (¹⁸F-AlF-NOTA-PEG₄-ZD2) for targeting extradomain-B fibronectin (EDB-FN), and evaluate its properties in vitro and in vivo.

¹⁸F-AlF-NOTA-PEG₄-ZD2 was prepared by one-step chelation labeling with Al¹⁸F. The radiochemical purity and in vitro stability were determined by high performance liquid chromatography (HPLC). The partition coefficient (logP) of ¹⁸F-AlF-NOTA-PEG₄-ZD2 was evaluated, and the cell uptake experiment was carried out (triple-negative breast cancer (MDA-MB-231) cells (1×10⁶/tube) were divided into 3 groups (n=3 per group); positive group, inhibition group, control group). MicroPET imaging was performed on MDA-MB-231 bearing nude mice (n=3) after ¹⁸F-AlF-NOTA-PEG₄-ZD2 injection (30, 60, 90, 120 min) and compared with blocking group (n=3, NOTA-PEG₄-ZQ₂ was preinjected at 0.5 h before ¹⁸F-AIF-NOTA-PEG_a-ZD2 injection). Independent-sample t test was used to analyze the data.

¹⁸F-AlF-NOTA-PEG₄-ZD2 was successfully prepared. The optimized radiochemical yield was (33.8±2.1)% (undecay corrected, n=8) and the radiochemical purity was >96%. After incubating 120 min at 37 ℃, the radiochemical purity of ¹⁸F-AlF-NOTA-PEG₄-ZD2 in human serum and PBS was >93%, indicating its good stability in vitro. The specific activity was (11.1±3.2) GBq/μmol, and logP was -1.43±0.05. The uptake value of tumor cells was (1.77±0.28) percentage applied activity (%AR)/10⁶ cells at 120 min post-injection in positive group, and the total uptake value of the inhibition group was (0.76±0.07) %AR/10⁶ cells (t=4.30, P=0.032). MicroPET imaging in tumor bearing nude mice showed that ¹⁸F-AlF-NOTA-PEG₄-ZD2 was mainly metabolized by the liver and kidneys. The tumor uptake value was (1.94±0.21) percentage activity of injection dose per gram of tissue (%ID/g) at 60 min post-injection and the tumor/muscle ratio was 3.80±0.25 at 90 min post-injection in the experimental group, while the tumor uptake value of tumor bearing nude mice in the blocking group was (0.43±0.09) %ID/g at 60 min post-injection (t=3.18, P=0.006).

¹⁸F-AlF-NOTA-PEG₄-ZD2 can be prepared simply with high labeling rate and good stability in vitro, with high tumor uptake and tumor/muscle ratio in microPET imaging, and good specificity and long tumor residence time. The probe has good application prospect in breast cancer with high expression of fibronectin subtype EDB-FN.

Fibronectins; Isotope labeling; Fluorine radioisotopes; Positron-emission tomography; Tomography, X-ray computed; Breast neoplasms; Tumor cells, cultured; Mice, nude