Image-Guided In Vivo Tracking of Splenocyte Dynamics Using Superparamagnetic Iron Oxide-Based Nanoparticles in a Rodent Model

< 0.001). Flow cytometry analysis of tumor tissues revealed a significantly higher accumulation of SPIOpICG-positive cells in the SPIOpICG-splenocyte group (50.45 ± 6.15%) compared to free SPIOpICG (16.10 ± 0.42%). Phenotypic analysis of positive cells revealed that macrophages, particularly the M2 subtype, constitute the predominant SPIOpICG-positive population within the tumor. These findings demonstrate that splenocyte-mediated delivery is largely driven by macrophage trafficking to tumor sites. This capability provides valuable insights into splenic immune cell trafficking and highlights splenocytes, particularly macrophages, as effective natural carriers for targeted nanoparticle delivery, offering a biocompatible platform for the development and optimization of immune cell-based immunotherapies.