JNM
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH RSS TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

First published online July 13, 2007, 10.2967/jnumed.107.040303
This Article
Right arrow Abstract Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in JNM
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Misra, P.
Right arrow Articles by Frangioni, J. V.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Misra, P.
Right arrow Articles by Frangioni, J. V.

Production of Multimeric Prostate-Specific Membrane Antigen Small-Molecule Radiotracers Using a Solid-Phase 99mTc Preloading Strategy

Preeti Misra1, Valerie Humblet1, Nadine Pannier2, Wolfgang Maison2 and John V. Frangioni1,3

1 Division of Hematology/Oncology, Beth Israel Deaconess Medical Center, Boston, Massachusetts; 2 Institut fur Organische Chemie, Universität Hamburg, Hamburg, Germany; and 3 Department of Radiology, Beth Israel Deaconess Medical Center, Boston, Massachusetts


Figure 1
View larger version (15K):
[in this window]
[in a new window]

  		FIGURE 1.  Highly anionic PSMA-targeting small-molecule ligands: chemical structures and M.W. for PSMA-targeting ligands used in this study.

 

Figure 2
Figure 2
Figure 2
Figure 2
View larger version (71K):
[in this window]
[in a new window]

  		FIGURE 2.  99mTc labeling strategies, solid-phase prelabeling, and purification of 99mTc-/Re-labeled MAS3 and MAS3-NHS. (A) General approaches for creating 99mTc-radiolabeled derivatives of small molecules and peptides include postlabeling (route 1) in presence of excess exchange ligand such as tartrate, solution-phase prelabeling using excess of exchange ligand (route 2), or solid-phase prelabeling (route 3) using Chelex 100 resin as described. (B) C18 HPLC radiochromatograms of conventional solution-phase prelabeling of 99mTc-MAS3 with excess tartrate (top left) and solid-phase prelabeling with Chelex 100 (bottom left). Solid-phase formation and purification of [99mTc-MAS3]-NHS (top right) and hydrolysis of NHS ester at pH 10 (bottom right). 99mTc-MAS3 and [99mTc-MAS3]-NHS elute at 14.1 and 23.5 min, respectively. 99mTc-Tartrate elutes at 13.5 min. (C) Simple, cartridge-based labeling and purification protocol to produce [99mTc-MAS3]-NHS is shown. Total elapsed time (brackets) and yield for each step are also shown. (D) C18 HPLC ELSD tracings (top) and mass spectra of major peak (bottom) for Re-MAS3 (left) and its NHS ester (right). Expected isotopic patterns for these Re derivatives are shown as insets. AU = absorbance units.

 

Figure 3
Figure 3
Figure 3
Figure 3
View larger version (71K):
[in this window]
[in a new window]

  		FIGURE 3.  Preparation, purification, and analysis of PSMA-specific radiotracers. (A) Single nucleophiles (primary amines) of small molecules from Fig. 1 were conjugated in 1 step to [99mTc-MAS3]-NHS using solid-phase preloading strategy described in text to create PSMA-specific radiotracers. (B) RP-HPLC analysis of compounds I–IV after solid-phase prelabeling using either 99mTc (left) or Re (right). Rt values for compounds Ia–IVa are shown, as are ES-TOF(–) mass spectra of peak for Re compounds (insets). AU = absorbance units. For comparison, Rt values for [99mTc-MAS3]-NHS and [Re-MAS3]-NHS on their optimized gradients are 23.5 and 10.4 min, respectively (Figs. 2B and 2D). (C) Serum protein binding and serum stability of solid-phase prelabeled 99mTc PSMA-specific small molecules. Compound 99mTc-IVa was incubated for 0 or 4 h at 37°C in PBS (top) or 100% serum (bottom) and then subjected to HPLC analysis. Samples in PBS were resolved on a Symmetry C18 column. Samples in serum were resolved on a 120-Å high-resolution gel-filtration column and also include absorbance (280 nm) tracings. Rt values for gel-filtration markers M1–M5 are shown as arrows. Marker Rt values were M1 = 6.6 min, M2 = 8.2 min, M3 = 9.2 min, M4 = 11.1 min, and M5 = 13.4 min. (D) Live cell-binding assay. PSMA-positive LNCaP cells grown on 96-well filter plates as described in text were incubated for 20 min at 4°C with monomeric 99mTc-Ia (top row) or trimeric 99mTc-IVa (bottom row) in presence of increasing concentrations of homologous nonradioactive test compound. Shown are results for monomeric Re-Ia (top row) and trimeric Re-IVa (bottom row) in TBS (left), PBS (middle), and 100% serum (right). Also shown are mean affinities ± 95% confidence intervals for 3 independent assays. N.D. = none detected.

 

Figure 4
View larger version (87K):
[in this window]
[in a new window]

  		FIGURE 4.  Radioscintigraphic imaging of 99mTc-labeled PSMA-specific radiotracers: Live cell binding of 99mTc-Ia (GPI monomer; M) and 99mTc-IVa (AdamGPI trimer, T) was performed in TBS (top row), PBS (middle row), and 100% serum (bottom row) for 20 min at 4°C using PSMA-positive LNCaP cells (left), PSMA-negative PC-3 cells (middle), and PSMA-negative TsuPR1 cells (right) grown on 96-well filter plates, followed by extensive washing. Cells were independently loaded with NIR fluorophore IR-786 to assess viability and confluence. Shown are white light (top), NIR fluorescence (middle), and {gamma}-detector (bottom) images of cells grown on 96-well filter plates.

 




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH RSS TABLE OF CONTENTS
JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY THE JOURNAL OF NUCLEAR MEDICINE
Copyright © 2007 by the Society of Nuclear Medicine.