Romih T, Drašler B, Jemec A, Drobne D, Novak S, Golobič M, Makovec D, Susič R, Kogej K
[ pdf ] [ site ] Science of the Total Environment, 2015

The aim of this study was to determine whether citric acid adsorbed onto cobalt ferrite (CoFe₂O₄) nanoparticles (NPs) influences the bioavailability of their constituents Co and Fe. Dissolution of Co and Fe was assessed by two measures: (i) in aqueous suspension using chemical analysis, prior to application onto the food of test organisms; and (ii) in vivo, measuring the bioavailability in the model terrestrial invertebrate (Porcellio scaber, Isopoda, Crustacea). The isopods were exposed to citric-acid-adsorbed CoFe₂O₄ NPs for 2 weeks, and tissue accumulation of Co and Fe was assessed. This was compared to pristine CoFe₂O₄ NPs, and CoCl₂ and Fe(III) salts as positive controls. The combined data shows that citric acid enhances free metal ion concentration from CoFe₂O₄ NPs in aqueous suspension, although in vivo, very similar amounts of assimilated Co were found in isopods exposed to both types of NPs. Therefore, evaluation of the dissolution in suspension by chemical means is not a good predictor of metal assimilation of this model organism; body assimilation of Co and Fe is rather governed by the physiological capacity of P. scaber for the uptake of these metals. Moreover, we propose that citric acid, due to its chelating properties, may hinder the uptake of Co that dissolves from citric-acid-adsorbed CoFe₂O₄ NPs, if citric acid is present in sufficient quantity.