A novel bimodal lipidic contrast agent for cellular labelling and tumour MRI.

We have synthesized a bimodal lipidic molecule bearing both fluorophore and contrast agent signatures on the same structure in order to create a robust bimodal liposome for both magnetic resonance imaging (MRI) and fluorescence microscopy utility. The dual-modality concept considered in the synthesis of this new paramagnetic and fluorescent lipid is valuable in that anatomical information (MRI) as well as very sensitive localization (ex vivo fluorescence microscopy) of signal, and therefore liposome biodistribution, is obtainable. Bimodal cationic and neutral PEGylated liposomes were formulated using this novel lipid probe and used to label cells in vitro and image human ovarian xenografts in vivo. Tumour signal enhancement was increased by over 6-fold post-administration of the neutral PEGylated liposomes, and was maintained at this level up to the 24 h end-point. Our results showed this lipid to be more effective and sensitive than the single signature paramagnetic lipid Gd.DOTA.DSA at cellular labelling and tumour MRI.