Magnetic layer-by-layer coated particles for efficient MRI of dendritic cells and mesenchymal stem cells

Aim: Cell detection by MRI requires high doses of contrast agent for generating image contrast. Therefore, there is a constant need to develop improved systems that further increase sensitivity, and which could be used in clinical settings. In this study, we devised layer-by-layer particles and tested their potential for cell labeling. Materials & methods: The advantages of layer-by-layer technology were exploited to obtain magnetic particles of controllable size, surface chemistry and magnetic payload. Results: Flexibility in size and surface charge enabled efficient intracellular delivery of magnetic particles in mesenchymal stem cells and dendritic cells. Owing to the high magnetic payload of the particles, high MRI contrast was generated, even for very low cell numbers. Subcutaneous injection of the particles and subsequent uptake by dendritic cells enabled clear visualization of dendritic cells homing towards nearby lymph nodes in mice. Conclusion: The magnetic particles offer several possibilities as efficient cellular MRI contrast agents for direct in vitro or in vivo cell labeling.