Phosphonate PEG Copolymers to control the USPIO stealthiness

For nanomedicine applications, there is a need to design advanced and cost-effective coatings, resistant to protein adsorption leading to increased biodistribution in vivo. In this study, phosphonate poly(ethylene glycol) copolymers were synthesized and used to coat 6nm and 13nm iron oxide particle. In vitro, PEGylated particles exhibit exceptional stability and low cellular uptake, of the order of 100 femtograms of iron per cell. In vivo, we developed an in vivo Dynamic Susceptibility Weighted MRI (7T) protocol to monitor the hepatic capture and clearance of the particles injected to mice as a function of the time. PEGylated coat of molecular weight 2000 gmol-1 show a 2hrs delay to liver uptake as compared to the commercially available USPIO Cliavist, indicating a direct correlation between the surface properties of the contrast agents and their stealthiness.