Magnetic chromatography improves colloidal and MRI attributes of magnetoliposomes enabling evaluation of the impact of size on biodistribution in an in vivo model of pancreatic cancer

Magnetic chromatography was exploited to fractionate suspensions of magnetoliposomes (SML: lumenfree lipid-encapsulated clusters of multiple magnetic iron-oxide nanoparticles) improving their colloidal properties and relaxivity (magnetic resonance image contrast capability). Fractionation (i) removed sub-populations that do not contribute to the MRI response, and thus (ii) enabled evaluation of the sizedependence of relaxivity for the MRI-active part, which was surprisingly weak in the 55-90 nm range. MC was therefore implemented for processing multiple PEGylated SML types having average sizes ranging from 85 to 105 nm, which were then shown to have strongly size-dependent uptake in an in vivo pancreatic cancer model. Hence for applications in cancer diagnosis, selection of SML of suitable size for the biological target is more important than size-dependence of relaxivity.