NIR imaging of vascular endothelial cells using Cy5.5-lectin conjugates

Abstract

The objective of this study was to develop a fluorescent near-infrared endothelial cell binding conjugate using Lycopersicon esculentum lectin and Cy5.5 N-hydroxysuccinimide ester for the purpose of imaging the microvascular network in mouse hearts under in vivo and ex vivo conditions. Cy5.5-lectin conjugate was synthesized with a dye/protein ratio of 2.90 ± 1.54 (n=6). Mouse hearts were successfully labelled in both in vivo and ex vivo and showed similar labelling patterns. Cy5.5-lectin labelling patterns and that of ICAM2 and FITC-lectin co-localized, indicating binding to endothelial cells. Finally, it was shown that Cy5.5-lectin is capable of visualizing, in real-time, areas of normal and abnormal heart perfusion at resolutions of 76.8 pixels/mm. Areas of the heart that were not perfused post-ligation displayed no Cy5.5 staining on histological sections and during real-time cardiac imaging of intact hearts showed minimal fluorescent signal (~35 a.u.) compared to areas where normal perfusion occurred (~150 a.u.).