Are they in or out? The elusive interaction between Qtracker(®)800 vascular labels and brain endothelial cells

AIM:Qtracker®800 Vascular labels (Qtracker®800) are promising biomedical tools for high-resolution vasculature imaging; their effects on mouse and human endothelia, however, are still unknown.MATERIALS & METHODS:Qtracker®800 were injected in Balb/c mice, and brain endothelium uptake was investigated by transmission electron microscopy 3-h post injection. We then investigated, in vitro, the effects of Qtracker®800 exposure on mouse and human endothelial cells by calcium imaging.RESULTS:Transmission electron microscopy images showed nanoparticle accumulation in mouse brain endothelia. A subset of mouse and human endothelial cells generated intracellular calcium transients in response to Qtracker®800.CONCLUSION:Qtracker®800 nanoparticles elicit endothelial functional responses, which prompts biomedical safety evaluations and may bias the interpretation of experimental studies involving vascular imaging.