Using colloidal AFM probe technique and XDLVO theory to predict the transport of nanoplastics in porous media.

The plastic concentration in terrestrial systems is orders of magnitude higher than that found in marine ecosystems, which has raised global concerns about their potential risk to agricultural sustainability. Previous research on the transport of nanoplastics in soil relied heavily on the qualitative prediction of the mean-field extended Derjaguin-Landau-Verwey-Overbeek theory (XDLVO), but direct and quantitative measurements of the interfacial forces between single nanoplastics and porous media are lacking. In this study, we conducted multiscale investigations ranging from column transport experiments to single particle measurements. The maximum effluent concentration (C/C0) of amino-modified nanoplastics (PS-NH2) was 0.94, whereas that of the carboxyl-modified nanoplastics (PS-COOH) was only 0.33, indicating PS-NH2 were more mobile than PS-COOH at different ionic strengths (1-50 mM) and pH values (5-9). This phenomenon was mainly attributed to the homogeneous aggregation of PS-COOH. In addition, the transport of PS-NH2 in the quartz sand column was inhibited with the increase of ionic strength and pH, and pH was the major factor governing their mobility. The transport of PS-COOH was inhibited with increasing ionic strength and decreasing pH. Hydrophilicity/hydrophobicity-mediated interactions and particle heterogeneity strongly interfered with interfacial forces, leading to the qualitative prediction of XDLVO, contrary to experimental observations. Through the combination of XDLVO and colloidal atomic force microscopy, accurate and quantitative interfacial forces can provide compelling insight into the fate of nanoparticles in the soil environment.

Aged microplastics enhance their interaction with ciprofloxacin and joint toxicity on Escherichia coli.

Microplastics (MPs) in natural environments undergo complex aging processes, changing their interactions with coexisting antibiotics, and posing unpredictable ecological risks. However, the joint toxicity of aged MPs (aMPs) and antibiotics to bacteria, especially at the molecular level, is unclear. In this study, non-thermal plasma technology was used to simultaneously simulate various radical oxidation and physical reactions that occur naturally in the environment, breaking the limitation of simple aging process in laboratory aging technologies. After aging, we investigated the altered properties of aMPs, their interactions with ciprofloxacin (CIP), and the molecular responses of E. coli exposed to pristine MPs (13.5 mg/L), aMPs (13.5 mg/L), and CIP (2 µg/L) individually or simultaneously. aMPs bound far more CIP to their surfaces than pristine MPs, especially in freshwater ecosystems. Notably, the growth of E. coli exposed to aMPs alone was inhibited, whereas pristine MPs exposure didn't affect the growth of E. coli. Moreover, the most differentially expressed genes in E. coli were induced by the coexposure of aMPs and CIP. Although E. coli depended on chemotaxis to improve its flagellar rotation and escaped the stress of pollutants, the coexposure of aMPs and CIP still caused cell membrane damage, oxidative stress, obstruction of DNA replication, and osmotic imbalance in E. coli. This study filled the knowledge gap between the toxicity of aMPs and pristine MPs coexisting with antibiotics at the transcription level, helping in the accurate assessment of the potential risks of MPs to the environment.

Evaluation of the Direct and Indirect Regulation Pathways of Glutathione Target to the Hepatotoxicity of Microcystin-LR.

Glutathione (GSH) plays crucial roles in regulating the hepatotoxicity of Microcystin-LR (MCLR) by inhibiting oxidative stress or by toxin conjugation. Based on MCLR conjugation product preparation and purification, the direct and indirect regulation pathways for GSH were fully evaluated. Protein phosphatase inhibition analysis verified that GSH conjugation was an effective pathway to regulate the inhibition effect of MCLR, while GSH had slight influence on the toxicity of MCLR. Research on oxidative stress showed that both regulation pathways could reduce the formation of reactive oxygen species (stimulated by MCLR and regulated by NADH oxidase) and regulate the adverse effects on antioxidant enzymes. By evaluating the contributions for both pathways, it could be found that the indirect pathway had significant contribution to eliminating cellular reactive oxygen species and regulating protein phosphatases inhibition, while the direct regulation pathway had moderate influence. As glutathione transferases facilitated the transformation of MCLR, the hepatotoxicity of MCLR could be effectively regulated by GSH conjugation pathway, especially with abundant exogenous GSH.