title: Aggregation Reverses the Carrier Effects of TiO2Nanoparticles on Cadmium Accumulation in the Waterflea Daphnia magna.
abstract: Our previous study reported that the Ca-dependent aggregation of polyacrylate-coated TiO2nanoparticles (PAA-TiO2-NPs) determines their routes of uptake by the waterflea Daphnia magna. Besides the effects of aggregation on NP bioaccumulation, how this process may influence the bioavailability of NP-adsorbed pollutants remains obscure. In the present study, the aggregation of PAA-TiO2-NPs was also adjusted through Ca. Then the accumulation and toxicity of Cd in D. magna were investigated in the presence and absence of the NPs. Although PAA-TiO2-NPs ameliorated Cd toxicity at both low and high Ca concentrations, the underlying mechanisms differed completely. At low Ca, the metal-NP complexes were accumulated by endocytosis and passive drinking, with both pollutants distributed throughout the daphnid. Nevertheless, Cd accumulation was reduced due to its rapid dissociation from the NPs during the endocytosis of the metal-NP complexes. At high Ca, the metal-NP complexes were actively ingested, Cd accumulation was induced, and both pollutants were concentrated in the daphnid gut. The aggregation-dependent effects of PAA-TiO2-NPs on Cd bioaccumulation were further evidenced by the distinct patterns of metal efflux from D. magna at different Ca concentrations. Overall, Cd adsorption by PAA-TiO2-NPs may either increase or reduce its bioaccumulation, as determined by the aggregation of the NPs.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China.
authors.forename: Ling-Yan
authors.initials: LY
authors.lastname: Tan
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China.
authors.forename: Shen
authors.initials: S
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China.
authors.forename: Zhong-Bo
authors.initials: ZB
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China.
authors.forename: Liu-Yan
authors.initials: LY
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China.
authors.forename: Ai-Jun
authors.identifier: 0000-0001-7681-2038
authors.initials: AJ
authors.lastname: Miao
mesh_terms: D000818:Animals; D002104:Cadmium; D003621:Daphnia / Q000187:drug effects*; D008670:Metals / Q000494:pharmacology; D053758:Nanoparticles; D014025:Titanium / Q000494:pharmacology; D014874:Water Pollutants, Chemical / Q000494:pharmacology
chemical_list: D008670:Metals; D014874:Water Pollutants, Chemical; D002104:Cadmium; D014025:Titanium