@article {Roberts839, author = {Sheryl Roberts and Eshita Khera and Crystal Choi and Tejas Navaratna and Jan Grimm and Greg M. Thurber and Thomas Reiner}, title = {Optoacoustic Imaging of Glucagon-like Peptide-1 Receptor with a Near-Infrared Exendin-4 Analog}, volume = {62}, number = {6}, pages = {839--848}, year = {2021}, doi = {10.2967/jnumed.120.252262}, publisher = {Society of Nuclear Medicine}, abstract = {Limitations in current imaging tools have long challenged the imaging of small pancreatic islets in animal models. Here, we report the first development and in~vivo validation testing of a broad-spectrum and high-absorbance near-infrared optoacoustic contrast agent, E4x12-Cy7. Our near-infrared tracer is based on the amino acid sequence of exendin-4 and targets the glucagon-like peptide-1 receptor (GLP-1R). Cell assays confirmed that E4x12-Cy7 has a high-binding affinity (dissociation constant, Kd, 4.6 {\textpm} 0.8 nM). Using the multispectral optoacoustic tomography, we imaged E4x12-Cy7 and optoacoustically visualized β-cell insulinoma xenografts in~vivo for the first time. In the future, similar optoacoustic tracers that are specific for β-cells and combines optoacoustic and fluorescence imaging modalities could prove to be important tools for monitoring the pancreas for the progression of diabetes.}, issn = {0161-5505}, URL = {https://jnm.snmjournals.org/content/62/6/839}, eprint = {https://jnm.snmjournals.org/content/62/6/839.full.pdf}, journal = {Journal of Nuclear Medicine} }