Polymeric liposomes-coated superparamagnetic iron oxide nanoparticles as contrast agent for targeted magnetic resonance imaging of cancer cells.

The purpose of this study was to use polymeric liposomes (PLs) with a targeting ligand (folate) to coat superparamagnetic iron oxide nanoparticles (SPIONs) and transfer the magnetic nanoparticles from organic phases to aqueous solutions, and further evaluate their efficacy as a magnetic resonance imaging (MRI) contrast agent. The formed nanoparticles exhibited a narrow range of size dispersity (core size of the particles is about 8-10 nm) and relatively high T2 relaxivities (r2 = 164.14 s(-1) mM(-1) for folate-PLs-coated SPIONs). The in vitro tumor cell targeting efficacy of the folate functionalized and PLs-coated SPIONs was evaluated upon observing cellular uptake of magnetite liposomes by HeLa cells, which overexpresses surface receptors for folic acid. In the Prussian blue staining experiments, cells incubated with folate-PLs-coated SPIONs showed much higher intracellular iron density than did the cells incubated with the folate-free PLs-coated SPIONs. Meanwhile, the MTT assay explains the negligible cell cytotoxicity of SPIONs and folate-PLs-coated SPIONs. In HeLa cells, the in vitro MRI study also indicates the better T2-weighted images in folate-PLs-coated SPIONs than in folate-free PLs-coated SPIONs.