Distribution and quantification of Prussian blue stained superparamagnetic iron oxide nanoparticles (SPIONs) on day 13 post-antigen-induced arthritis (AIA) induction. Photomicrographs of Prussian-blue-stained sections showing an example of the distribution of SPIONs (red arrows) in the synovium of untreated animal (A) versus a Dexa-treated animal (B) on day 13 post-AIA induction at 1.5 times magnification. Quantification of the area (C) and number (D) of Prussian-blue-stained SPIONs on day 13 post-AIA induction. Photomicrographs of Prussian-blue-stained sections were scanned and the images were analyzed for the area (C) and the number (D) of SPIONs using Tissue Studio® software. Four sections were quantified and averaged per animal. Data points are mean ± standard error of the mean and n = 5 per group. *P = 0.005 (A) and 0.016 (B) compared to the untreated control group.