Abstract

Multimodal imaging probes have attracted the interest of ongoing research, for example, for the surgical removal of tumors. Modular synthesis approaches allow the construction of hybrid probes consisting of a radiotracer, a fluorophore and a targeting unit. We present the synthesis of a new asymmetric bifunctional cyanine dye that can be used as a structural and functional linker for the construction of such hybrid probes. 68Ga‐DOTATATE, a well‐characterized radiopeptide targeting the overexpressed somatostatin receptor subtype 2 (SSTR2) in neuroendocrine tumors, was labeled with our cyanine dye, thus providing additional information along with the data obtained from the radiotracer. We tested the SSTR2‐targeting and imaging properties of the resulting probe 68Ga‐DOTA‐ICC‐TATE in vitro and in a tumor xenograft mouse model. Despite the close proximity between dye and pharmacophore, we observed a high binding affinity towards SSTR2 as well as elevated uptake in SSTR2‐overexpressing tumors in the positron emission tomography (PET) scan and histological examination.

Highlights

  • Introduction help the surgeon to first localize the tumor via the positron emission tomography (PET) or SPECT scan, followed by the identification of tumor margins through fluorescence imaging, which enables the resection of affected areas.[4]

  • We present a new design approach for the construction of multimodal imaging probes and employ the fluorophore as the linking unit between chelator and targeting moiety

  • Multimodal imaging using PET or SPECT together with fluorescence imaging has emerged as a promising tool for the development of new diagnostics and treatment options.[1]

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Summary

Department of Nuclear Medicine

For PET or SPECT studies, the DOTA chelator can in general form stable complexes with 64Cu, 68Ga and 111In.[20] The methylene unit between the aromatic moiety and the amine of the dye was essential for the amide coupling Without this additional methylene unit, harsh conditions were required being incompatible with acid-labile protecting groups. In comparison to other design approaches, the resulting hybrid probe becomes relatively compact with the dye in direct proximity to the pharmacophore

Spectroscopic properties
In vitro studies
In vivo imaging and biodistribution
Histological examination
Conclusion
General information
Elution was performed using a linear gradient with solvents A and
In vitro tests
Conflict of Interest

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