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Study of the combined-carrier dual mechanism of polyethylene terephthalate microplastics and nonylphenol ethoxylates on bovine serum albumin
Summary
Tiny plastic particles from bottles and packaging (PET microplastics) can act like sponges, soaking up hormone-disrupting chemicals called nonylphenol ethoxylates and carrying them into our bodies, and stomach acid conditions actually make these plastics release even more of the chemical. When both the plastic and chemical hitch a ride together, they bind more strongly to a key blood protein and disrupt its normal shape and function more than either one does alone, suggesting this "combo effect" could pose a greater health risk than scientists previously assumed by studying microplastics and chemicals separately.
Microplastics, as carriers of environmental pollutants, may influence their biological effects through adsorption. The adsorption mechanism of polyethylene terephthalate microplastics (PET MPs) on the endocrine disrupting compound nonylphenol ethoxylate (NPE) is studied. Furthermore, the effect of the PET MPs–NPE complex on the structure and function of the carrier protein bovine serum albumin (BSA) is further explored. The adsorption process of PET MPs on NPE conforms to the pseudo-second-order kinetic model (R2 = 0.9985) and Freundlich model (R2 = 0.9241), and belongs to a spontaneous, endothermic, and entropy-increasing process. PET MPs function as effective NPE carriers, achieving a desorption rate of 59.29% in acidic buffer solution (pH 1.2), suggesting that ingestion may enhance NPE release risk in vivo. Multispectral analysis showed that free PET MPs and NPE were bound to Site II of BSA through hydrogen bonding and van der Waals forces, altering BSA’s secondary structure. When PET MPs and NPE coexist, they exhibit a combined effect, manifested by significantly enhanced binding affinity with BSA (Kb from 5.39 × 104 M−1 to 2.71 × 105 M−1) and higher disturbance to BSA conformation than a single component. The PET MPs–NPE complex triggers pronounced conformational changes in BSA, suppresses esterase-like activity, and alters thiol content.