Synthesis and application of [18F]FDG-RGD

Objectives: Based on the principle of oxime formation, the ¹⁸F labeling of polypeptides can be achieved via a reaction between an aldehyde group-containing ¹⁸F-prosthetic group and an aminooxy-modified polypeptide. The focus of this study was to investigate the one-step synthesis of 2-[¹⁸F]fluoro-2-deoxyglucose ([¹⁸F]FDG)-RGD from open-ring [¹⁸F]FDG and the aminooxy-modified RGD peptide cyclo(RGDfK)-ONH₂ and to study the biological distribution of [¹⁸F]FDG-RGD in a nude mouse model of human neuroglioma.

Methods: The aminooxy-modified RGD peptide cyclo(RGDfK)-ONH₂ was used as the precursor to react with [¹⁸F]FDG at 100 ℃ and pH 1.5-2.5 for 30 min to synthesize [¹⁸F]FDG-RGD. The labeling rate, radiochemical purity, in vitro stability of the product were measured, and the biological distribution of [¹⁸F]FDG-RGD in tumor-bearing nude mice at 30 min, 60 min and 120 min were analyzed.

Results: The labeling rate of [¹⁸F]FDG-RGD was 14.5%, the radiochemical purity was greater than 95%. [¹⁸F]FDG-RGD was mainly excreted by the kidneys, and blood clearance was rapid. One hour after injection, the radioactive uptake values ​​for the kidney, liver, small intestine, muscle and blood were (1.95 ± 0.15)% ID/g, (0.77 ± 0.21)% ID/g, (0.64 ± 0.05)% ID/g, (0.26 ± 0.17)% ID/g and (0.42 ± 0.05)% ID/g, respectively. One hour after injection, the uptake of [¹⁸F]FDG-RGD by tumors was (1.83 ± 0.12)% ID/g, Tumor/Muscle (T/M) was 7.03 ± 0.04. Conclusion: The synthesis of [¹⁸F]FDG-RGD can be achieved via oximation. This method is simple and easy to promote. The blood clearance of [¹⁸F]FDG-RGD is rapid, its radioactive background is low, its binding to integrin αvβ3 receptor is specific, its uptake by tumors is extremely high,; therefore, [¹⁸F]FDG-RGD maybe be used for the imaging of integrin-positive tumors.

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