Rapid and efficient cell labeling with a MRI contrast agent by electroporation in the presence of protamine sulfate

Aims: To investigate various protocols for magnetic labeling of human cancer cells with ferumoxides with a view to developing an effective and fast technique for potential clinical use in MRI. Materials & methods: Transfection methods utilizing poly-L-lysine and protamine sulfate (PS), electroporation, and combination of PS with electroporation were evaluated in this in vitro study. Results: Although transfection was more effective in terms of uptake rates (95-100%) and intracellular iron concentrations (4.01-7.34 pg/cell), all transfection agents required prolonged incubation. By contrast, electroporation yielded fast labeling but with a lower efficacy (68-75%, 1.63-2.59 pg/cell). The addition of PS to electroporation increased the labeling efficacy (80-91%, 2.84-4.16 pg/cell) and protected cell viability. This combined method also resulted in the best T-2*-shortening effect in the in vitro cellular MRI. Conclusion: The combined PS-electroporation method provides a fast and efficient protocol for ferumoxide-based cellular imaging and therapeutic procedure.