J Korean Med Sci.  2007 Jun;22(3):405-411. 10.3346/jkms.2007.22.3.405.

Folate Receptor Targeted Imaging Using Poly (ethylene glycol)-folate: In Vitro and In Vivo Studies

• Kim SL
• Jeong HJ
• Kim EM
• Lee CM
• Kwon TH
• Sohn MH

• KMID: 1778345
• DOI: http://doi.org/10.3346/jkms.2007.22.3.405

Abstract

The aim of this study was to ascertain the folate receptor (FR) targetability by an in vitro study and to acquire FR-targeted images in vivo models by using synthetic folate conjugates. PEG-folate was synthesized and labeled with (99m)Tc and fluorescein isothiocynate (FITC). Cell uptake studies were carried out in KB cells (FR-positive) and A549 cells (FR-negative) using FITC- and the (99m)Tc-labeled conjugates. The radiolabeled conjugate was intravenously injected to KB tumor xenografted mice. After it was injected, gamma images were recorded at 30 min, 1, 2, 3 and 4 hr. Cell uptake studies showed a difference between the KB cells and the A549 cells by flow cytometry analysis and gamma counting. On in vivo images, the tumor-tonormal muscle ratio was greater than 4. It ascertained that the PEG-folate conjugate specifically binds to the FR expressed on tumor cells in vitro. Moreover, it was possible to acquire the FR-targeted gamma images using PEG-folate conjugates in tumor models.

Keyword

Polyethylene Glycol; Folate Receptor; Gamma Camera Imaging

MeSH Terms

Animals
Carrier Proteins/*metabolism
Cell Line, Tumor
Female
Fluorescein-5-isothiocyanate/pharmacology
Folic Acid/*metabolism
Humans
Image Processing, Computer-Assisted
Mice
Mice, Nude
Microscopy, Fluorescence
Neoplasm Transplantation
Polyethylene Glycols/*chemistry
Receptors, Cell Surface/*metabolism
Technetium/*chemistry
Time Factors

Figure

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  Fig. 1 1H NMR spectra of PEG (Jeffamine) and the folate-PEG conjugate.

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  Fig. 2 Flow cytometric analysis of the KB (A) cells and A549 (B) cells treated with PEG-FITC (thick black line), PEG-folate-FITC (thin black line), and PEG-folate-FITC added folic acid (gray) in the culture media without folic acid.

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  Fig. 3 Fluorescent microscopic pictures of KB cells with folate-PEG-FITC when folic acid was absent (A, D), and present in the culture media (B, E) and the A549 cells with folate-PEG-FITC when folic acid was absent (C, F).

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  Fig. 4 ITLC chromatography of 99mTc PEG-folate (A), labeling efficiency of 99mTc PEG-folate (B), and the stability of 99mTc PEG-folate in human serum (C).

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  Fig. 5 Cellular uptake of radiolabeled PEG-folate in KB and A549 cells (A) and the study on contrast using PEG, PEG-folate and PEGfolate with folic acid in the KB cells (B). Data represent the means of three independent experiments±SD (*, p<0.05).

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  Fig. 6 Representative images of a mouse treated with 99mTc PEG-folate (A) and the competition images with folic acid (B).

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  Fig. 7 Intensity comparison and analysis between tumor and non-tumor. Data represent the means of three independent experiments±SD.

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