There is a paucity of in vivo assays to investigate the potential deleterious effects of plastic-laden compounds in the gastrointestinal tract of mammals, compared to in vitro testing and ecotoxicity assays in marine organisms. This work aims to fill this gap through a comprehensive evaluation of the acute toxicokinetics and bioavailability of bisphenol A (BPA)-adsorbed medium-density polyethylene (PE) microplastics (MPs) (ca. 3000 μg BPA/g), with a mean particle size of 136 μm, which were administered via oral gavage at a mere 0.67 mg BPA/kg body weight for 24 h using a murine model. The determination of plasma BPA-glucuronide revealed that BPA associated with MPs (PE-BPA) is bioavailable to a similar extent to that of freely dissolved BPA, with Area Under the Curves (AUC) values of 1249 ± 182 and 928 ± 276 μg h·L^-1 for the 0 → 6 h interval (AUC_0→6h), and 3586 ± 526 and 2325 ± 634 μg h·L^-1 for the 0 → 24 h interval (AUC_0→24h), corresponding to PE-BPA and free BPA, respectively. Several biomarker assays of the small intestine and liver, and the investigation of the gut barrier function were conducted to elucidate the potential deleterious effects of PE-BPA as compared to BPA and PE alone. Acute exposure to PE-BPA increased the expression of the detoxification biomarkers multidrug resistance protein 1 (MDR1) and UDP-glucuronosyltransferase 2b1 (UGT2b1) in the jejunum, particularly when PE and BPA occurred together, likely due to the extended intestinal residence time of the BPA-laden MPs. Oxidative stress markers, such as superoxide dismutase activity, and inflammatory responses, evaluated by myeloperoxidase activity, were also elevated in the PE-BPA group, suggesting a defensive response but without evidence of oxidative damage as determined by the malondialdehyde levels. In conclusion, the findings suggest that BPA associated with MPs exhibits similar bioavailability than that of freely dissolved BPA, with the subsequent activation of detoxification pathways and inflammatory responses.

Langevin Dynamics numerical simulations have been used to compute the force profiles that dipolar polymer brushes exert onto a penetrating colloidal particle. It has been observed that force profiles are strongly influenced by externally applied fields: at large distances from the grafting surface, a force barrier appears, and at shorter distances a region with lower repulsive forces develops. Furthermore, with the right combination of polymer grafting density, polymer chain length and strength of the external field, it is possible to observe in this intermediate region both the existence of net attractive forces onto the penetrating particle and the emergence of a stationary point. The existence of these regions of low repulsive or net attractive forces inside the dipolar brushes, as well as their dependence on the different parameters of the system can be qualitatively reasoned in terms of a competition between steric repulsion forces and Kelvin forces arising from the dipolar mismatch between different regions of the system. The possibility to tune force profile features such as force barriers and stationary points via an external field paves the way for many potential surface–particle-related applications.

Langevin Dynamics numerical simulations have been used to compute the force profiles that dipolar polymer brushes exert onto a penetrating colloidal particle. It has been observed that force profiles are strongly influenced by external applied fields: a force barrier at large distances from the grafting surface appears, and at shorter distances a region with lower repulsive forces develops. Furthermore, for a right combination of polymer grafting density, polymer chain length and strength of the external field, it is possible to observe in such intermediate region the existence of net attractive forces onto the penetrating particle, and the emergence of a stationary point. The existence of these regions of low repulsive or net attractive forces inside the dipolar brushes, as well as their dependence on the different parameters of the system can be qualitatively reasoned in terms of a competition between steric repulsion forces and Kelvin forces arising from the dipolar mismatch between different regions of the system. The possibility to tune force profile features such as force barriers and stationary points via an external field paves the way for many potential surface-particle related applications.

Using Langevin Dynamic simulations, we show two examples of how the competition between entropic forces and interactions arising from the mismatch between the non-polar and dipolar moieties present in a medium (Kelvin Forces) can be used to tune the interaction between colloids and polymers via an external field