Durable Mesenchymal Stem Cell Labelling by Using Polyhedral Superparamagnetic Iron Oxide Nanoparticles

Small polyhedral superparamagnetic iron oxide (SPIO) nanoparticles (<10 nm) coated with a thin layer of silica were prepared (SPIO@SiO2 and SPIO@SiO2-NH2). Surface modification of the small polyhedral silica-coated SPIO nanoparticles with amines led to substantially higher mesenchymal stem cell (MSC) labelling efficiency without the use of additional transfecting agents. Therefore, amine surface-modified nanoparticles (SPIO@SiO2-NH2) appeared to be the preferred candidate for MSC labelling. In vitro studies demonstrated that controlled labelling Of SPIO@SiO2 and SPIO@SiO2-NH2 did not cause MSC death or proliferation inhibition. MSCs labelled with SPIO@SiO2-NH2 nanoparticles retained differentiation potential and showed osteogenic, adipogenic and chondrogenic differentiations. The noncytotoxic polyhedral SPIO@SiO2-NH2 nanoparticle-labelled MSCs were successfully implanted in rabbit brain and erector spinae muscle, and demonstrated long-lasting, durable MRI labelling efficacy after 8-12 weeks.