Negatively Charged Magnetite Nanoparticle Clusters as Efficient MRI Probes for Dendritic Cell Labeling and In Vivo Tracking

Abstract

Cell labeling and tracking via magnetic resonance imaging (MRI) has drawn much attention for its noninvasive property and longitudinal monitoring functionality. Employing of imaging probes with high labeling efficiency and good biocompatibility is one of the essential factors that determine the outcome of tracking. In this study, negatively charged superparamagnetic iron oxide (PAsp‐PCL/SPIO) nanoclusters are developed for dendritic cell (DC) labeling and tracking in vivo. PAsp‐PCL/SPIO has a diameter of 124 ± 41 nm in DLS, negatively charged surface (zeta potential = −27 mV), and presents high T 2 relaxivity (335.6 Fe mm −1 s−1) and good DC labeling efficiency. Labeled DCs are unaffected in their viability, proliferation, and differentiation capacity, and have an excellent MR imaging sensitivity in vitro. To monitor the migration of DCs into lymphoid tissues in vivo, which will be related to the final immunotherapy results, T 2‐wighted and T 2‐map imaging of popliteal nodes at different points in time are acquired under a clinical 3 T scanner after subcutaneous injection of a certain number of labeled DCs at hindleg footpads of mice. The signal intensities decreasing and T 2 values shortening of ipsilateral popliteal nodes are significant and display a time‐ and dose‐dependence, showing DCs' migration to the draining lymph nodes.