Optoacoustic imaging of Glucagon-like Peptide 1 Receptor with a near-infrared exendin-4 analog

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, E4_x12-Cy7. Our near infrared tracer (E4_x12-Cy7) is based on the amino acid sequence of exendin-4 and targets the glucagon-like peptide-1 receptor (GLP-1R). Cell assays confirmed that E4_x12-Cy7 has a high binding affinity (IC50 = 4.6 ± 0.8 nM). Using the multi-spectral optoacoustic tomography (MSOT), we imaged E4_x12-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.