Comparative analysis of lignin peroxidase and laccase responses to graphene-related nanomaterials

: Graphene-related materials (GRMs) are revolutionizing sectors such as electronics, energy storage, agriculture, and biomedicine due to their exceptional properties. However, concerns are emerging about their environmental impact, particularly regarding their persistence, potential toxicity to aquatic ecosystems, and challenges in safe disposal. These issues highlight the need for more robust sustainable-by-design and risk-assessment strategies. In this context, this research investigated the influence of GRMs on lignin peroxidase (LiP) and laccase (Lac), key enzymes involved in lignin breakdown with significant potential in bioremediation. These enzymes are crucial for degrading complex molecules, and understanding their interaction with GRMs could provide valuable insights into the degradation of 2D nanomaterials, particularly graphene oxide (GO), few-layer graphene (FLG), and reduced graphene oxide (rGO). In-vitro enzymatic assays conducted with varying GRMs concentrations (12.5, 25.0, and 50.0 μg/mL) revealed that Lac remained unaffected, while LiP exhibited a noteworthy reduction in catalytic activity, particularly in the presence of GO at the highest concentration. A sequestration study to quantify the bioavailable fraction, confirmed these effects, indicating significant enzyme loss, notably with GO at 50 μg/mL. These findings prompted a mechanistic exploration of enzyme inhibition dynamics, revealing the complex nature of GRM-catalytic enzyme processes. By considering factors such as zeta potential (electrostatic forces), hydrophobicity, dispersion stability and oxidation state, this study addresses a key knowledge gap and provides a foundation for understanding these interactions, offering crucial insights into the environmental fate of GRMs and guiding their sustainable use and management.