(597c) Molecular Modeling and Simulations Uncovering the Sorption of Toxic Compounds on Unamended and Carnitine-Amended Montmorillonite Clays

In the event of natural disasters such as flooding or hurricanes, soil and sediment contaminated with toxic compounds can be transported to areas with high levels of human contact. Montmorillonite clays can be considered as highly promising sorbents for the mitigation of toxic compounds, including aflatoxin, glyphosate and paraquat^1,2. Furthermore, previous intervention studies and clinical trials have shown that montmorillonite clay significantly decreased biomarkers of aflatoxin exposure and could be safely consumed by humans and animals on a short-term basis. Thus, montmorillonite clay can be a promising sorbent to be integrated into the diet of humans or animals to combat the exposure and toxicity of toxic compounds. Despite their promise, the sorption or binding of toxic compounds to montmorillonite clay is not well understood at an atomistic level, limiting the discovery of toxic compounds that could be sorbed onto the clay – thereby reducing their contact with humans or animals – and limiting the development of novel sorbent amendments that can facilitate toxin binding on active surfaces of clay. In this study, we modeled both unamended and carnitine-amended montmorillonite clay in the presence of a variety of toxic compounds involved in the production of plastics, independently, using multiple multi-ns molecular dynamics (MD) simulations in CHARMM. Following the MD simulations, we performed energy calculations and structural analyses using in-house developed programs to elucidate and predict the binding of toxic compounds to the unamended and carnitine-amended clays. From our analyses, we predicted the binding propensities and binding persistence of different toxic compounds for the clays, the key binding modes of the different toxic compounds upon binding to the clays, and the energetic favorability of each of the toxic compounds binding to the clays. Importantly, the results derived from computational MD simulations were compared with and were in line with in vitroexperimental results from adsorption isotherms, including binding capacity, binding affinity, and thermodynamics of sorption (free energy and enthalpy).

1. Awuor, A.O., Yard, E., Daniel, J.H., Martin, C., Bii, C., Romoser, A., Oyugi, E., Elmore, S., Amwayi, S., Vulue, J., Zitomer, N.C., Rybak, M.E., Phillips, T.D., Montgomery, J.M., Lewis, L.S., 2017. Evaluation of the efficacy, acceptability and palatability of calcium montmorillonite clay used to reduce aflatoxin B1 dietary exposure in a crossover study in Kenya. Food Addit. Contam. 34, 93−102.
2. Wang, M. Orr, A.A., He, S., Dalaijamts, C., Chiu, W.A., Tamamis, P., Phillips, T.D., 2019. Montmorillonites Can Tightly Bind Glyphosate and Paraquat Reducing Toxin Exposures and Toxicity. ACS Omega. 4, 17702–17713.