MicroPIXE mapping of nanoparticles unravels differential toxicological effects on tadpoles

Abstract

In this work, South American tadpoles (R. arenarum) were exposed to aqueous Au and ZnO nanoparticles (NPs),respectively, to perform an acute ecotoxicological assessment. A 50-MeV 16O5+ beam was employed to map bymicroPIXE Au- and Zn- histological microdistribution in order to propose a mechanism underlying intoxication.The beam was focused with the aid of the Tandar Laboratory heavy-ion microprobe onto a spot of 5 μm indiameter. 2D elemental distribution maps were constructed. Total reflection X-Ray Fluorescence spectroscopy(TXRF) was used for bulk analysis of previously digested samples.The results indicated that, in all cases, NPs were highly bioconcentrated (>300 times). Nonetheless, Au NPswere blocked by aggregation in the digestive system and undetectable ([Au] < 1.5 μg.g􀀀 1) in other tissues,whereas ZnO NPs were dispersed in several tissues. The differential microdistribution of Au and ZnO NPs allowedto explain the toxicological features and could lead to a dissimilar biomagnification throughout the aquatic foodweb.