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In vivo imaging of GLP-1R with a targeted bimodal PET/fluorescence imaging agent.

Brand C, Abdel-Atti D, Zhang Y, Carlin S, Clardy SM, Keliher EJ, Weber WA, Lewis JS, Reiner T - Bioconjug. Chem. (2014)

Bottom Line: The bimodal imaging agent (64)Cu-E4-Fl was synthesized in good radiochemical yield and specific activity (RCY = 36%, specific activity: 141 μCi/μg, >98% radiochemical purity).The agent showed good performance in vivo and ex vivo, visualizing small xenografts (<2 mm) with PET and pancreatic β-cell mass by phosphor autoradiography.We believe that our procedure could become relevant as a protocol for the development of bimodal imaging agents.

View Article: PubMed Central - PubMed

Affiliation: Radiochemistry and Imaging Sciences Service and §Molecular Imaging and Therapy Service, Department of Radiology, ∥Molecular Pharmacology and Chemistry Program, and ⊥Center for Molecular Imaging and Nanotechnology, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.

ABSTRACT
Accurate visualization and quantification of β-cell mass is critical for the improved understanding, diagnosis, and treatment of both type 1 diabetes (T1D) and insulinoma. Here, we describe the synthesis of a bimodal imaging probe (PET/fluorescence) for imaging GLP-1R expression in the pancreas and in pancreatic islet cell tumors. The conjugation of a bimodal imaging tag containing a near-infrared fluorescent dye, and the copper chelator sarcophagine to the GLP-1R targeting peptide exendin-4 provided the basis for the bimodal imaging probe. Conjugation was performed via a novel sequential one-pot synthetic procedure including (64)Cu radiolabeling and copper-catalyzed click-conjugation. The bimodal imaging agent (64)Cu-E4-Fl was synthesized in good radiochemical yield and specific activity (RCY = 36%, specific activity: 141 μCi/μg, >98% radiochemical purity). The agent showed good performance in vivo and ex vivo, visualizing small xenografts (<2 mm) with PET and pancreatic β-cell mass by phosphor autoradiography. Using the fluorescent properties of the probe, we were able to detect individual pancreatic islets, confirming specific binding to GLP-1R and surpassing the sensitivity of the radioactive label. The use of bimodal PET/fluorescent imaging probes is promising for preoperative imaging and fluorescence-assisted analysis of patient tissues. We believe that our procedure could become relevant as a protocol for the development of bimodal imaging agents.

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In vivo PET imaging with 64Cu-E4-Fl. (A) Evaluationof the weighted blood half-life. (B) Decay-corrected small animalPET images (4–5 h) of 916–1 tumor-bearing (<2 mm)mice; intravenous injection of 64Cu-E4-Fl (335 ± 35μCi) in 200 μL PBS (4% DMSO) (nonblocked) and coinjectionof 64Cu-E4-Fl (335 ± 35 μCi) and E4x12 (100 fold excess) in 200 μL PBS (4% DMSO). (C) Tumor uptakein nonblocked (1.1 ± 0.1%ID/g) and blocked (0.2 ± 0.1%ID/g)PET images. (D) Biodistribution study with 916–1 tumor bearingmice.
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fig4: In vivo PET imaging with 64Cu-E4-Fl. (A) Evaluationof the weighted blood half-life. (B) Decay-corrected small animalPET images (4–5 h) of 916–1 tumor-bearing (<2 mm)mice; intravenous injection of 64Cu-E4-Fl (335 ± 35μCi) in 200 μL PBS (4% DMSO) (nonblocked) and coinjectionof 64Cu-E4-Fl (335 ± 35 μCi) and E4x12 (100 fold excess) in 200 μL PBS (4% DMSO). (C) Tumor uptakein nonblocked (1.1 ± 0.1%ID/g) and blocked (0.2 ± 0.1%ID/g)PET images. (D) Biodistribution study with 916–1 tumor bearingmice.

Mentions: In order to explore the potential applications of 64Cu-E4-Fl 6 for in vivo imaging, we first determinedthe blood half-life of 64Cu-E4-Fl (Figure 4A). After tail vein injection of the imaging agent (30–35μCi, n = 4), we observed a weighted t1/2 of 10.1 min. The half-life was fitted toa two-phase exponential decay curve, resembling a multicompartmentmodel with a fast agent distribution and a slow agent eliminationphase.


In vivo imaging of GLP-1R with a targeted bimodal PET/fluorescence imaging agent.

Brand C, Abdel-Atti D, Zhang Y, Carlin S, Clardy SM, Keliher EJ, Weber WA, Lewis JS, Reiner T - Bioconjug. Chem. (2014)

In vivo PET imaging with 64Cu-E4-Fl. (A) Evaluationof the weighted blood half-life. (B) Decay-corrected small animalPET images (4–5 h) of 916–1 tumor-bearing (<2 mm)mice; intravenous injection of 64Cu-E4-Fl (335 ± 35μCi) in 200 μL PBS (4% DMSO) (nonblocked) and coinjectionof 64Cu-E4-Fl (335 ± 35 μCi) and E4x12 (100 fold excess) in 200 μL PBS (4% DMSO). (C) Tumor uptakein nonblocked (1.1 ± 0.1%ID/g) and blocked (0.2 ± 0.1%ID/g)PET images. (D) Biodistribution study with 916–1 tumor bearingmice.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4215873&req=5

fig4: In vivo PET imaging with 64Cu-E4-Fl. (A) Evaluationof the weighted blood half-life. (B) Decay-corrected small animalPET images (4–5 h) of 916–1 tumor-bearing (<2 mm)mice; intravenous injection of 64Cu-E4-Fl (335 ± 35μCi) in 200 μL PBS (4% DMSO) (nonblocked) and coinjectionof 64Cu-E4-Fl (335 ± 35 μCi) and E4x12 (100 fold excess) in 200 μL PBS (4% DMSO). (C) Tumor uptakein nonblocked (1.1 ± 0.1%ID/g) and blocked (0.2 ± 0.1%ID/g)PET images. (D) Biodistribution study with 916–1 tumor bearingmice.
Mentions: In order to explore the potential applications of 64Cu-E4-Fl 6 for in vivo imaging, we first determinedthe blood half-life of 64Cu-E4-Fl (Figure 4A). After tail vein injection of the imaging agent (30–35μCi, n = 4), we observed a weighted t1/2 of 10.1 min. The half-life was fitted toa two-phase exponential decay curve, resembling a multicompartmentmodel with a fast agent distribution and a slow agent eliminationphase.

Bottom Line: The bimodal imaging agent (64)Cu-E4-Fl was synthesized in good radiochemical yield and specific activity (RCY = 36%, specific activity: 141 μCi/μg, >98% radiochemical purity).The agent showed good performance in vivo and ex vivo, visualizing small xenografts (<2 mm) with PET and pancreatic β-cell mass by phosphor autoradiography.We believe that our procedure could become relevant as a protocol for the development of bimodal imaging agents.

View Article: PubMed Central - PubMed

Affiliation: Radiochemistry and Imaging Sciences Service and §Molecular Imaging and Therapy Service, Department of Radiology, ∥Molecular Pharmacology and Chemistry Program, and ⊥Center for Molecular Imaging and Nanotechnology, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.

ABSTRACT
Accurate visualization and quantification of β-cell mass is critical for the improved understanding, diagnosis, and treatment of both type 1 diabetes (T1D) and insulinoma. Here, we describe the synthesis of a bimodal imaging probe (PET/fluorescence) for imaging GLP-1R expression in the pancreas and in pancreatic islet cell tumors. The conjugation of a bimodal imaging tag containing a near-infrared fluorescent dye, and the copper chelator sarcophagine to the GLP-1R targeting peptide exendin-4 provided the basis for the bimodal imaging probe. Conjugation was performed via a novel sequential one-pot synthetic procedure including (64)Cu radiolabeling and copper-catalyzed click-conjugation. The bimodal imaging agent (64)Cu-E4-Fl was synthesized in good radiochemical yield and specific activity (RCY = 36%, specific activity: 141 μCi/μg, >98% radiochemical purity). The agent showed good performance in vivo and ex vivo, visualizing small xenografts (<2 mm) with PET and pancreatic β-cell mass by phosphor autoradiography. Using the fluorescent properties of the probe, we were able to detect individual pancreatic islets, confirming specific binding to GLP-1R and surpassing the sensitivity of the radioactive label. The use of bimodal PET/fluorescent imaging probes is promising for preoperative imaging and fluorescence-assisted analysis of patient tissues. We believe that our procedure could become relevant as a protocol for the development of bimodal imaging agents.

Show MeSH
Related in: MedlinePlus