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High-throughput screening of combined toxicity of nanoplastics and coexisting pollutants using luminescent bacterium
Summary
Researchers developed a high-throughput screening method using luminescent bacteria to rapidly assess the combined toxicity of nanoplastics with heavy metals and antibiotics. They found that most metal-nanoplastic combinations produced antagonistic effects, while some antibiotic combinations showed additive or synergistic toxicity depending on nanoplastic surface properties. The study provides an efficient new tool for evaluating the complex mixture toxicity of nanoplastics with co-occurring pollutants in water.
Micro/nanoplastics (MNPs) commonly coexist with contaminants such as heavy metals and antibiotics in aquatic environments, potentially inducing complex joint toxicity. However, conventional approaches for MNP-pollutant combined toxicity assessment are typically challenged by inefficiencies, high costs, and labor-intensive procedures. In this study, a high-throughput platform using microplate-based inhibition assays with a luminescent bacterium (Vibrio qinghaiensis sp.-Q67), was applied to systematically evaluate the combined toxicity of four polystyrene nanoplastics (PS-NPs), varying in size and surface functionalization, with seven heavy metals and five antibiotics. Results showed that metal cations (Cu, Zn, Pb, Cd, and Cr) and chlortetracycline combined with PS-NPs primarily induced antagonistic or additive toxicity, whereas anions (CrO and AsO) and antibiotics (tetracycline, oxytetracycline, norfloxacin, and ciprofloxacin) exhibited synergistic or additive toxicity. Smaller PS-NPs (50 nm) amplified the toxicity interactions compared to 100 nm PS-NPs. Carboxyl-modified PS-NPs exhibited the most pronounced antagonistic effects with cations, while amino-modified PS-NPs favored amplified synergistic effects with CrO. The combined effects were intensified at higher PS-NP concentrations and at moderate co-contaminant concentrations (i.e., 1/5 or 1 × the median effect concentration). Antibiotics with higher water solubility exhibited more pronounced synergistic effects with PS-NPs, and the antagonism intensities for metal cations followed an order of Pb > Cu > Cr > Zn > Cd. This high-throughput strategy efficiently assessed multifactorial impacts on combined toxicity, providing systematic insights into the toxic interaction patterns between MNPs and pollutants.