Use of micro-PIXE for elemental characterization and iron uptake evaluation in zebrafish larvae exposed to iron oxide nanoparticles

We report on the evaluation of iron content and biodistribution in zebrafish larvae (Dario rerio) exposed to dextran-coated superparamagnetic iron oxide nanoparticles (SPION-DX) using the micro-PIXE technique. We compare results of elemental 2D maps and Fe quantification obtained from two different sample preparation procedures: one using sagittal slices prepared by cryo-sectioning and another using entire dehydrated larvae. Independently of the preparation method used, the Fe content in the tissues of exposed animals is significantly higher than in the controls, but the increase is not proportional to the exposure level. In addition, 2D elemental maps show a somewhat homogeneous Fe distribution in the larvae, with some samples showing a slight enhancement in Fe content near the gut. From the PIXE data a curve correlating the exposure (nanoparticle concentration in the fish water) to the iron content in the body was obtained, which shows a saturation trend towards high exposure doses.