An Insight into the Combined Toxicity of 3,4-Dichloroaniline with Two-Dimensional Nanomaterials: From Classical Mixture Theory to Structure-Activity Relationship

Abstract

The assessment and prediction of the toxicity of engineered nanomaterials (NMs) present in mixtures is a challenging research issue. Herein, the toxicity of three advanced two-dimensional nanomaterials (TDNMs), in combination with an organic chemical (3,4-dichloroaniline, DCA) to two freshwater microalgae (Scenedesmus obliquus and Chlorella pyrenoidosa), was assessed and predicted not only from classical mixture theory but also from structure-activity relationships. The TDNMs included two layered double hydroxides (Mg-Al-LDH and Zn-Al-LDH) and a graphene nanoplatelet (GNP). The toxicity of DCA varied with the type and concentration of TDNMs, as well as the species. The combination of DCA and TDNMs exhibited additive, antagonistic, and synergistic effects. There is a linear relationship between the different levels (10, 50, and 90%) of effect concentrations and a Freundlich adsorption coefficient (K_F) calculated by isotherm models and adsorption energy (E_a) obtained in molecular simulations, respectively. The prediction model incorporating both parameters K_F and E_a had a higher predictive power for the combined toxicity than the classical mixture model. Our findings provide new insights for the development of strategies aimed at evaluating the ecotoxicological risk of NMs towards combined pollution situations.

Keywords: aquatic toxicity; combined pollution; in silico; multifunctional nanomaterials; structure-activity relationship.

Figure 1

Concentration-response curves for the growth inhibition of the two freshwater microalgae exposed to the DCA in the absence and presence of Mg-Al-LDH (A,D), Zn-Al-LDH (B,E), and GNP (C,F). Data are mean ± SD (n = 3).

Figure 2

Summary of the experimentally determined (observed) and predicted toxicity response of DCA in the absence and presence of Mg-Al-LDH (A,D), Zn-Al-LDH (B,E), and GNP (C,F). Schematic diagram (G) shows the types of joint interactions between the studied ENPs and DCA towards algal cells.

Figure 3

Variation of different effect concentrations (EC_X, X = 10, 50, and 90) of DCA in the presence of 0.5 (A,C,E,G) and 5 (B,D,F,H) mg/L of Mg-Al-LDH, Zn-Al-LDH, and GNP with the Freundlich isotherm fitting parameter (K_F) (A,B,E,F) and simulated adsorption energies (E_a) (C,D,G,H).

Figure 4

Plot of experimentally determined (observed) values of effect concentrations (EC_X, X = 10, 50, and 90) versus predicted values by the Abbott model (A,C) and parametric prediction models (B,D). The dashed line represents perfect agreement between experimental and calculated values.