The overuse of plastics is a global waste of resources and a serious threat to the ecological safety of oceans, lakes and soils. This raises concerns about the migration of nanoplastics from contaminants into food and the associated health risks. Previous research has identified pathways by which plastics in the environment gradually break down into nanoplastics (1 to 100 nm) under external conditions such as solar radiation and biological decomposition. It has also been found that the roots of plants (including food plants) can take up nanoplastics and accumulate them in the roots, stems, and leaves, leading to contamination in the food chain. However, it is still unclear whether nanoplastics can eventually reach the fruits of crops grown in soils contaminated with nanoplastics, and what effects nanoplastics have on, for example, fruit nutrient quality. Therefore, understanding the pathways by which nanoplastics enter fruits and their effects is essential to explore the associated risks to ecosystems and human health.
On October 17, 2022, Professor Ruhong Zhou from College of Life Science, Zhejiang University and Shanghai Institute for Advanced Study, Zhejiang University and collabrators jointly published Evidence and impacts of nanoplastic accumulation on crop grains (DOI: 10.1002/advs.202202336), identifying for the first time the molecular mechanisms by which nanoplastics can accumulate in crops and affect their nutrient quality.
Using scanning electron microscopy, laser confocal spectroscopy, Raman spectroscopy, and Fourier infrared spectroscopy, theydemonstrated that polystyrene nanoplastics (PS-NPs, 80 nm) can accumulate in the fruits of the crops peanut and rice. In addition, the interaction between nanoplastics and plant cell membranes was investigated using coarse-grained molecular dynamics simulations. The simulations revealed that Polystyrene nanoplastics (PS-NPs, 80nm) have strong van der Waals interactions with membrane phospholipids as they approach the cell membrane and further enter the membrane through encapsulation endocytosis, revealing the molecular mechanism of nanoplastics entry into fruit cells.
It was found that the accumulation of nanoplastics in fruits at high concentrations in soil (PS -80nm, 250mg/kg) increased the rate of empty husks in rice, which in turn affected the fruit set rate, and also reduced the average grain weight of peanut. In addition, nanoplastics negatively affected the nutritional quality of fruits, such as a decrease in trace elements, unsaturated fatty acids and amino acids at different levels. Transcriptional analysis revealed that the expression of some of the relevant synthetic transporter proteins was down-regulated and that differential adsorption of different amino acids by nanoplastics could also be a factor in reducing the corresponding amino acid content in the fruit. Simulations of molecular dynamics with all atoms confirmed the strong adsorption of nanoplastics to the amino acids Met, Ile, Leu, Phe, Tyr, Lys, Arg, and Pro. Among them, Phe and Tyr can form π-π-stacking interactions with the benzene ring of the nanoplastic. The positively charged amino acids Lys and Arg also have strong cation-π interactions with the nanoplastics. The mechanism by which nanoplastics disrupt amino acid homeostasis in plant fruits was elucidated by a combination of experiments and molecular dynamics simulations.
To access the work please check https://doi.org/10.1002/advs.202202336. The work combined researchers from biology, computational biology and nanotechnology, and reflect the advantages of multidisciplinary research. It was funded by the National Key R&D Program of China, the grants from the National Natural Science Foundation of China, the Fundamental Research Funds for Central Universities, the National Independent Innovation Demonstration Zone Shanghai Zhangjiang Major Projects and the Starry Night Science Fund.