In vitro characterization of micron-sized iron oxide particle (MPIO)-labeled porcine liver cells. Native and labeled cells cultivated in the SlideReactor showed no differences in morphology (scale bars: 100 μm) (A, B). Labeling had no adverse effects on particle load (C), cellular integrity (D, E), or metabolic activity (F) (one-way ANOVA and Student’s f-test with Bonferroni correction, *p < 0.05). A transient increase of levels of aspartate aminotransferase (AST) was found at day 2 following enzymatic resuspension. Experiments were repeated with cells from five individual donors. Threshold for detection of MPIO-labeled liver cells by abdominal MRI. Dilution series of labeled and native cells investigated by 3D Tl-weighted liver acquisition with volume acceleration (LAVA) sequences (G). The signal-to-noise ratio (SNR) of labeled cells was significantly lower compared to native cells from at least 10,000 cells (H) (two-tailed Student’s t-test, *p < 0.05).