Natural Organic Ingredients Reduce Aquatic Toxicity of Nanoparticles

Although the effects of natural organic matter (NOM) on nanoparticles (NPs) in the food chain have not been investigated, studies have found that NOM present in aquatic environments influences the toxicity and behavior of NPs.

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YouStudy: Effect of organic matter on trophic transfer of silver nanoparticles in aquatic food chains. Image Credit: Tim7914/Shutterstock.com

In an article recently published in the Journal of Hazardous Materials, researchers chose Escherichia coli (E. coli) bacterial species and Tetrahymena thermophila (T. thermophila) protozoa to investigate the effect of NOM on trophic transfer, toxicity, and bioaccumulation of silver nanoparticles (Ag NPs).

The results revealed that NOM reduced the toxicity of Ag NPs at T. thermophila and E. coli through influence mechanisms such as reduction of Ag NP accumulation or Ag . formation⁺ ionic complexes, which are specific for the type of organism and NOM. Ag NP biomagnification on T. thermophila is through trophic transfer.

Three typical NOMs show approximately twofold increase in trophic transfer factor (TTF) Ag NPs, where NOM reduces capacity T. thermophila to secrete Ag during exocytosis. This study provides insight into the influence of NOM in disrupting the ecological disturbance caused by TN Ag entering the food chain.

NP Applications and Their Effect on the Food Chain

NP has been widely used in various fields. Therefore, it is very important to monitor the risks posed to ecology and human health due to the excessive presence of NPs. The extensive use of TN Ag and its large production results in its accumulation in water bodies causing pollution in aquatic systems. In addition, Ag NPs found on the surface of water bodies can be ingested by various microorganisms and aquatic organisms, causing toxic effects.

Consumption of Ag NPs in contaminated food or water leads to their bioaccumulation in living systems. Moreover, previous reports mentioned that trophic transfer is the main pathway for NP uptake by predators. Furthermore, bio amplification of NPs by trophic transfer through the food chain can affect higher trophic level organisms.

Various factors influence the trophic transfer of NPs, and the impact of NOM is of major concern due to its ubiquity in the aquatic environment. In addition, NOM is adsorbed on the NP surface to form a layer, which significantly affects the transformation, environmental behavior, and bioavailability of the NPs. One of the previous reports mentioned a reduction in the toxic effect caused by Ag NPs due to their complexation with NOM, forming a water-soluble Ag-NOM complex.

Effect of NOM on Tropical Transfer of Aquatic Food Chain Ag NPs

In this study, the researchers created a food chain model by E. coli bacteria and T. thermophila protozoa belonging to two different trophic levels and investigated the impact of NOM on trophic transfer of Ag NPs. Transmission electron microscopy (TEM) images showed that the Ag NPs had a mean particle diameter of 23.61 ± 0.20 nanometers, and the hydrodynamic diameters were 50.98 and 59.95 nanometers in concentrations of 0.1 and 1 milligram per liter of fresh water. artificial, respectively.

NOM is a variety of complex organic compounds such as polysaccharides, proteins, humic acids (HA), and lipids. Therefore, bovine serum albumin (BSA), sodium alginate (SA), and HA were used as representative elements of the previously mentioned complex organic compounds present in NOM. The presence of BSA and SA did not affect the hydrodynamic diameter of Ag NPs. However, HA promotes NP agglomeration, resulting in a higher hydrodynamic diameter.

Consequently, polyvinyl pyrrolidone (PVP) is used as a surface coating agent on Ag NPs because it can control the morphology of Ag NPs and prevent their agglomeration. Investigation of the bioaccumulation of Ag NPs and their toxic effects on E. coli in the presence of HA, BSA, and SA was performed. Then, the mechanism of the impact of NOM on the biological fate and trophic transfer of Ag NPs was studied in the freshwater food chain, which is based on trophic transfer from E. coli to T. thermophila.

Conclusion

In summary, the researchers experimentally demonstrated that Ag NPs accumulated in bacteria were transferred later to higher trophic level organisms, resulting in biomagnification of Ag NPs in the bacteria. T. thermophila from E. coli. Protozoa with high phagocytic capacity enhance trophic transfer of Ag NPs, which leads to loss of their motility. Furthermore, the contaminated cells could be ingested by natural predators and lead to accelerated Ag NP biomagnification throughout the food web.

NOM also alters Ag . accumulation⁺ ions in E. coli bacterial species, consequently preventing their elimination by T. thermophila during exocytosis. Thus the presence of NOM in the aquatic environment affects the trophic transfer of Ag NPs and it is very important to draw attention to the biological impact of NOM on the fate and transfer of NPs in the food chain.

Reference

Liang, D., Fan, W., Wu, Y., Li, X., Dong, Z., Wang, Y. (2022) Effect of Organic Matter on Trophic Transfer of Silver Nanoparticles in Aquatic Food Chains. Journal of Hazardous Materials. https://www.sciencedirect.com/science/article/pii/S0304389422013140?via%3Dihub

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