Novel bimodal iron oxide particles for efficient tracking of human neural stem cells in vivo.

We validated novel bimodal iron oxide particles as substitute of ferumoxides for efficient labeling of human neural stem cells (NSCs). The dextrane-coated FeraTrack Direct (FTD)-Vio particles have additional far-red fluorophores for microscopic cell analysis. MR relaxometry, spectrophotometric iron determination and microscopy are used for characterization in vitro and in vivo. Efficient uptake is not transfection agent-dependent. FTD-Vio594 labeling had no influence on viability, proliferation, migration and differentiation capacity. It allows MRI-based tracking of engrafted NSCs in mouse brain up to 11 days, complemented by bioluminescence imaging of firefly luciferase expressed by the engrafted cells. Our results highlight the FTD-Vio594 particles as safe and sensitive substitute of ferumoxides for longitudinal tracking of NSCs in preclinical studies.