Synthesis and biological evaluation of diethylenetriamine pentaacetic acid-polyethylene glycol-folate: a new folate-derived, (99m)Tc-based radiopharmaceutical.
(99m)Technetium-labeled diethylenetriamine pentaacetic acid-polyethylene glycol-folate (DTPA-PEG-folate) was synthesized and tested as a radiopharmaceutical agent, which targeted the lymphatic system with metastatic tumor. Folic acid was reacted with H2N-PEG-NH2 to yield H2N-PEG-folate. After purification by anion-exchange chromatography, the product was reacted with cyclic DTPA. By removal of unreacted DTPA by size-exclusion chromatography, DTPA-PEG-Folate was obtained. Fluorescein-5-isothiocyanate (FITC)-labeled DTPA-PEG-folate and DTPA-PEG-OCH3 were prepared via a dicyclohexylcarbodiimide-mediated coupling. In vitro competitive binding test showed that the uptake of [125I] folic acid was inhibited by DTPA-PEG-folate and the 50% inhibitory concentration was 4.37 pmol/L (R2 = 0.9922). The relative affinity of DTPA-PEG-FITC was 0.18 for human folate receptor comparing with folic acid. In cultured tumor cells, uptake of fluorescence-labeled DTPA-PEG-folate was found to increase significantly in folate-deficient medium compared with that of untargeted DTPA-PEG-OCH3 and FITC-ethylenediamine. The competition with free folic acid blocked the cell uptake of DTPA-PEG-folate. These results confirmed the DTPA-PEG-folate entered into KB cells through the folate receptor endocytosis pathway in vitro. The radiolabeled yield of [(99m)Tc] DTPA-PEG-folate was in excess of 98%, and specific activities of 7.4 kBq (0.2 microCi/microg) were achieved. After subcutaneous injection, [(99m)Tc] DTPA-PEG-folate exhibited an initial increase and successive decline of accumulation in popliteal nodes in normal Wistar rats. Expect for the kidney, uptake by other tissues was rather low. In a normal rabbit imagine study, the lymphatic vessels were readily visualized by single-photon-emission computed tomography following subcutaneous injection of [(99m)Tc] DTPA-PEG-folate. In conclusion, the [(99m)Tc] DTPA-PEG-folate conjugate may have a potential as a lymphatic tumor-targeted radiopharmaceutical.
Liu
Min
M
Fudan-Pharmco Targeting Drug Research Center, Department of Pharmaceutics, School of Pharmacy, University of Fudan, Shanghai, 200032, People's Republic of China.
Xu
Wen
W
Xu
Ling-Jie
LJ
Zhong
Gao-Ren
GR
Chen
Shao-Liang
SL
Lu
Wei-Yue
WY
D000818:Animals; D045744:Cell Line, Tumor; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D005492:Folic Acid / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D008856:Microscopy, Fluorescence; D004369:Pentetic Acid / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011817:Rabbits; D019275:Radiopharmaceuticals / Q000737:chemistry* / Q000494:pharmacology*; D051381:Rats; D013667:Technetium / Q000737:chemistry*
D019275:Radiopharmaceuticals; D011092:Polyethylene Glycols; D013667:Technetium; D004369:Pentetic Acid; D005492:Folic Acid; D016650:Fluorescein-5-isothiocyanate