Abstract

Micro- and nanoplastics (MNPs), formed through the degradation of larger plastic waste, can be detected even in remote environments and have been shown to enter the food chain and the human body. Increasing experimental evidence points to their potential epigenetic and mutagenic effects, suggesting direct interactions with DNA. However, the molecular-level mechanisms behind these effects remain unexplored.

In our earlier study [1], we showed that positively charged polystyrene chains can induce a conformational transition in DNA from the canonical B form toward a more A-like structure. In this work, we explore through molecular dynamics simulations how different nanoplastics interact with DNA, through comparing an array of neutral and positively charged polymers. As a model system, we practically relevant DNA sequences, as well as repeating AT- and CG-rich sequences.

To generate DNA–nanoplastic complexes, we employed simulated annealing and high-temperature equilibrium simulations. While simulated annealing worked well for neutral systems, it proved less suitable for positively charged complexes, where short simulations at elevated temperature were more effective. The resulting structures were then simulated in aqueous environment. We found that neutral polystyrene, polyethylene, and nylon-6,6 oligomers tend to dissociate from DNA, indicating weak interactions. In contrast, positively charged polystyrene derivatives form stable complexes and induce pronounced structural changes in the DNA double helix, typically shifting it from B-DNA toward A-like conformations. Increasing the charge density on the polymer further makes these effects even more pronounced. Furthermore, we comparing the interaction energies of B-DNA structures to other conformations reveals that the strongly interacting, charged plastics tend to induce even more severe changes in the DNA conformations.

Thus, our results consistently show that they can significantly change DNA structure. This suggests that nanoplastics, in particular charged polymers, may have a direct impact on DNA-related biological processes.

References

[1] M. Varenicja, O. Hollóczki, Nano Lett. 25 (44), 15890-15894 (2025)