Due to its near-infrared excitation, we surmised that a Cy7-based dye, LUXendin762, might allow intravital labeling of GLP1R, visible using the widely available and non-invasive IVIS in vivo imaging systems. We first tested LUXendin762 in cellulo in SNAP-GLP1R:CHO-K1 cells and in keeping with its pharmacology were able to detect strong membrane-labelling, with little evidence of intracellular accumulation, again pointing to the high performance of cyaninebased dyes (Figure ). LUXendin762 was next used to label primary islets, again showing cell-membrane localization (Supplementary Figure ), shown to be GLP1R-positive using validated monoclonal antibody (Supplementary Figure ). No spectral overlap could be detected between Cy5 (LUXendin645) and Cy7 (LUXendin762) channels (Supplementary Figure ).