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PET Micro(nano)plastics Modulate Metformin–Albumin Binding and Species-Specific Bacterial Responses
Summary
New research shows that tiny plastic particles from common PET plastics (like water bottles) can change how the diabetes drug metformin binds to blood proteins, potentially affecting how the drug behaves in the body. The study also found that this plastic-drug combo affected two common bacteria differently, boosting growth of E. coli while suppressing growth of Staph bacteria (but increasing its biofilm formation, which can make infections harder to treat). While this was a lab study and not a test in living people, it raises questions about how everyday plastic exposure might interact with medications and gut bacteria in ways scientists are just beginning to understand.
Metformin is a widely used antidiabetic drug that may enter biological and environmental systems together with micro/nanoplastics; however, their combined effects on protein interactions and microbial responses remain insufficiently understood. This study investigated how polyethylene terephthalate micro/nanoplastics (PET MNPs) influence metformin interactions with bovine serum albumin (BSA) and the subsequent responses of Escherichia coli and Staphylococcus aureus. BSA–metformin systems were conditioned with three PET MNP loads and increasing metformin concentrations. The resulting particle-depleted filtrates were evaluated using fluorescence spectroscopy, ultraviolet–visible spectroscopy, the Bradford assay, Rayleigh light scattering, turbidity, dithiothreitol-based oxidative potential, and reactive oxygen species (ROS) measurements. Bacterial growth, superoxide dismutase activity, glutathione-related thiol antioxidant response, lipid peroxidation, ROS generation, and biofilm formation were also assessed. PET MNP conditioning altered the fluorescence responses of tryptophan and tyrosine, modified BSA-associated absorbance, and produced non-linear changes in protein accessibility, aggregation-related scattering, turbidity, and oxidative indicators. The bacterial responses were species-specific. Escherichia coli showed increased bacterial growth under several exposure conditions, whereas Staphylococcus aureus exhibited reduced growth following metformin addition, particularly at the highest PET MNP load. Staphylococcus aureus also showed consistently elevated biofilm formation and a pronounced transient ROS increase under the high-PET, low-metformin condition. These findings indicate that upstream PET MNP conditioning can modify the physicochemical and biological properties of the filter-passing BSA–metformin phase, leading to concentration-dependent and species-specific bacterial responses.