Differences in Engineered Nanoparticle (NP) Surface Physicochemistry Revealed by Investigation of Changes in Copper Bioavailability during Sorption to NPs in the Aqueous Phase

ABSTRACT

Sorption of chemical substances to nanoparticles (NPs) in the aqueous phase strongly influence NP physicochemisty, and investigations of these complex interactions can provide important insight on environmental fate of NPs. The objective of this study was to use differences in copper (Cu) bioavailability to investigate aqueous‐phase sorption with NPs of different physicochemistry (Si, perovskite and TiO₂ NPs). Sorption of Cu with NPs was assessed by presence of adsorbent in water and onto NP surface after ultra‐centrifugation, and by changes in copper bioavailability under static conditions during exposure of larval zebrafish, and under conditions of continuous agitation during exposure of alga Chlorella vulgaris. The presence of TiO₂ NPs reduced total Cu in the water column and Cu bioavailability (measured by growth inhibition, mortality, and metallothionein 2 gene expression) confirming Cu sorption to TiO₂ NPs. Nanoparticle surface area was the most important factor to affect Cu sorption indicated by less bioavailable Cu in presence of smaller TiO₂ NPs. The surface area effect was consistent regardless the exposure conditions (algal continuous agitation or zebrafish static water) and further supported by the lowest total Cu concentration in the water column in the presence of the smallest NP. Results differed with other NP types (i.e. Si NPs) in which Cu sorption was indicated by analytical chemistry, but sorption was not sufficient to significantly alter Cu bioavailability. The bioavailability tests did not indicate Cu sorption with perovskite NPs. Results demonstrate that surface area critically influences sorption, Cu sorption as measured by bioavailability is not affected by agitation or static conditions, and that Cu sorption differs among types of NPs indicating differences among their surface physicochemistry. This article is protected by copyright. All rights reserved

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