In Vivo LipoCEST CA Accumulation Around U87 Mice Brain Tumor Demonstrated by In Vivo CEST MRI & Ex Vivo Fluorescence Microscopy

Julien Flament¹, Franoise Geffroy¹, Boucif Djema¹, Benoit Theze², Aline Perrin¹, Christelle Medina³, Caroline Robic³, Marc Port³, Franck Lethimonnier¹, Gilles Bloch¹, Denis Le Bihan¹, Fawzi Boumezbeur¹

LipoCEST are a promising class of contrast agents for MR-based molecular imaging. However, recently similar PEGylated stealth paramagnetic liposomes have been shown to be avidly taken up by macrophages. For LipoCEST CA, similar cellular uptake could be extremely detrimental for its detection in vivo. In this study, we injected i.v 10mL/kg b.w. of PEGylated LipoCEST CA with rhodamine on its surface and managed to detect its accumulation around a U87 mice brain tumor in vivo using CEST-MRI. This result constitutes to our knowledge the first visualization of paramagnetic LipoCEST CA after i.v injection confirmed by ex vivo fluorescence microscopy.