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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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Related in: MedlinePlus

Comparisonof autoradiographic and optical imaging for the visualizationof β-cell mass. (A) H&E staining, fluorescent (GFP and NIR)and phosphor autoradiography images of a pancreatic histological slide(upper panels), as well as high magnification of an islet rich area(lower panels). (B) Signal intensity plots of a linear area of eachimaging modality (GFP, NIR fluorescence, and autoradiography) image.
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fig5: Comparisonof autoradiographic and optical imaging for the visualizationof β-cell mass. (A) H&E staining, fluorescent (GFP and NIR)and phosphor autoradiography images of a pancreatic histological slide(upper panels), as well as high magnification of an islet rich area(lower panels). (B) Signal intensity plots of a linear area of eachimaging modality (GFP, NIR fluorescence, and autoradiography) image.

Mentions: We next compared the twodifferent modalities of 64Cu-E4-Flat high resolution by using the radionuclide 64Cu for phosphorautoradiography and the fluorochrome sulfo-Cy5 for fluorescent imaging(Figure 5A)—both on identical histologyslides. First, phosphor autoradiography was performed with a pancreaticsection, followed by fluorescent imaging of the same histologicalslide to record the fluorescent signals of GFP and 64Cu-E4-Fl.At both low and high resolution, there was a good correlation of bothimaging modalities with regard to islet visualization. Intensity profileanalysis, however, shows that the alignment of GFP positive areasand 64Cu-E4-Fl is more accurate than the alignment of GFPpositive areas and phosphor autoradiography. While the differencesare less apparent at low resolution (Figure 5A), the comparison at high resolution (Figure 5B) illustrates the stark differences between fluorescence and autoradiography.


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)

Comparisonof autoradiographic and optical imaging for the visualizationof β-cell mass. (A) H&E staining, fluorescent (GFP and NIR)and phosphor autoradiography images of a pancreatic histological slide(upper panels), as well as high magnification of an islet rich area(lower panels). (B) Signal intensity plots of a linear area of eachimaging modality (GFP, NIR fluorescence, and autoradiography) image.
© Copyright Policy
Related In: Results  -  Collection

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

fig5: Comparisonof autoradiographic and optical imaging for the visualizationof β-cell mass. (A) H&E staining, fluorescent (GFP and NIR)and phosphor autoradiography images of a pancreatic histological slide(upper panels), as well as high magnification of an islet rich area(lower panels). (B) Signal intensity plots of a linear area of eachimaging modality (GFP, NIR fluorescence, and autoradiography) image.
Mentions: We next compared the twodifferent modalities of 64Cu-E4-Flat high resolution by using the radionuclide 64Cu for phosphorautoradiography and the fluorochrome sulfo-Cy5 for fluorescent imaging(Figure 5A)—both on identical histologyslides. First, phosphor autoradiography was performed with a pancreaticsection, followed by fluorescent imaging of the same histologicalslide to record the fluorescent signals of GFP and 64Cu-E4-Fl.At both low and high resolution, there was a good correlation of bothimaging modalities with regard to islet visualization. Intensity profileanalysis, however, shows that the alignment of GFP positive areasand 64Cu-E4-Fl is more accurate than the alignment of GFPpositive areas and phosphor autoradiography. While the differencesare less apparent at low resolution (Figure 5A), the comparison at high resolution (Figure 5B) illustrates the stark differences between fluorescence and autoradiography.

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