Elucidating the leaching effect of micro/nanoplastics on the binding, structural, and oxidative characteristics of bovine serum albumin, and impact on cytotoxicity and oxidative stress in the human lung cancer cell line, A549

Abstract

Proteins like albumin are found in various environmental, living systems, and applications. It is known that functional, conformational and sorption properties of proteins are significantly affected by various surrounding conditions and chemicals. Moreover, micro/nanoplastics are an emerging issue for environment, living systems and industrial applications, and they can easily leach, sorb and/or desorb chemicals resulting medium characteristics. However, the impact of micro/nanoplastics on chemical and biological behaviors of protein is lacking. Herein, we investigated the interactions between bovine serum albumin and polyethylene terephthalate micro/nanoplastics using binding, structural and oxidative characteristics of protein by UV-VIS, fluorescence and Raman spectroscopy, as well as molecular docking. In addition, the biological impact of non-treated and micro/nanoplastic-treated proteins was examined using cytotoxicity (mitochondrial activities and membrane integrity) and oxidative stress (antioxidant, reactive oxygen species, catalase, glutathione reductase, superoxide dismutase) of human lung epithelial cell-A549 in vitro model. The binding results showed that micro/nanoplastics had affinity to protein and varied by exposure concentration and duration. Further molecular simulation found that micro/nanoplastics to bind to the active site of protein, which is the cause for its structural and functional changes. Raman spectra confrm the structural changes in the protein after the treatments. Moreover, the protein chemical (e.g., zeta potentials, aromatic side chain and folding) and oxidative indicators were significantly affected. The exposure of lung cells to non-treated and micro/nanoplastic-treated proteins showed different mitochondrial and membrane activities. The oxidative stress indicators revealed that antioxidant, reactive oxygen species and their balance had an impact, and the superoxide dismutase and glutathione reductase were more influenced on the cell viabilities compared to catalase. The correlation results also indicated that folding, aromatic chain, quenching constant and oxidative potentials of protein were more effective indicators on the cell responses of micro/nanoplastics-treated proteins than zeta potentials. All the results indicated the side-effect of micro/nanoplastics on protein owing to the leaching and sorption.