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Biodegradable nanoplastics potentiate cadmium quantum dot developmental neurotoxicity in embryonic stem cells via synergistic interactions
Summary
Scientists found that "biodegradable" nanoplastics, marketed as eco-friendly alternatives to regular plastics, aren't necessarily harmless, especially when combined with other pollutants. In lab tests using stem cells, these biodegradable nanoplastics teamed up with toxic cadmium particles (used in electronics and some consumer products) to cause more harm to developing nerve cells than either substance did alone, by helping the cadmium get inside cells and damaging protective cell barriers. This matters because it suggests that even "green" plastics could make other environmental toxins more dangerous when combined, a risk that stand
Biodegradable nanoplastics like poly(ε-caprolactone) (PCL) are increasingly used as green alternatives, yet their interactions with environmental co-occurrence engineered nanomaterials like cadmium-containing quantum dots (Cd-QDs) remain poorly understood. Here, using a mouse embryonic stem cell differentiation model, we showed that Cd-QDs and poly(ε-caprolactone) nanoparticles (PCL-NPs) at individually subcytotoxic concentrations (0.076 and 1.52 mg/L, respectively) synergistically impaired neural differentiation. The observed mixture toxicity exceeded concentration-addition model predictions. Fluorescence spectroscopy, together with particle characterization in differentiation medium, supported physicochemical association and heteroaggregation between PCL-NPs and Cd-QDs, accompanied by a 2.3-fold increase in intracellular Cd-QD accumulation. Mechanistically, co-exposure triggered sequential membrane damage, including ROS-induced lipid peroxidation disrupted membrane integrity, increased fluidity/permeability, inhibited Ca²⁺-ATPase and Na⁺-K⁺-ATPase, and impaired ABC efflux pumps (P-gp/MRP2). These changes were associated with reduced Neurod1 and Map2 expression and impaired neural differentiation. Rifampicin intervention alleviated membrane dysfunction and restored neural differentiation, supporting the functional involvement of transporter-associated cellular defense while not excluding other protective pathways. Collectively, these findings demonstrate that PCL-NPs can potentiate Cd-QD toxicity by enhancing intracellular accumulation and disrupting interconnected membrane and efflux-defense processes, revealing mixture effects that may be overlooked by conventional single-material toxicity assessments.