Butylparaben-Loaded Aged Polystyrene Nanoplastics Amplify Its Toxicity in <i>Microcystis aeruginosa</i> via Quorum Sensing Suppression and Enhanced Microcystin-LR Release

Aged nanoplastics are emerging pollutants in aquatic environments, but the effects of their loaded pollutants on cyanobacteria are still poorly understood. This study evaluated the adsorption of butylparaben (BP) by pristine (PS) and aged polystyrene nanoplastics (APS) and prepared BP-loaded aged PS to analyze their effects on <i>Microcystis aeruginosa</i>. The results showed that APS had stronger BP adsorption and translocation capacity, with APS increasing BP adsorption by 4.34-fold and significantly enhancing its bioconcentration in <i>M. aeruginosa</i>. Compared with the PS-BP treatment, the 1.13 ng/g APS-BP treatment significantly inhibited algal growth, exacerbated cell membrane damage and oxidative stress, and promoted MC-LR synthesis and release. Transcriptome analyses and molecular docking showed that BP inhibited quorum sensing (QS) by binding to luxR, whereas APS further enhanced the binding affinity of BP and blocked the binding of <i>N</i>-acylhomoserine lactone, a natural QS signaling molecule, to its receptor, amplifying the QS inhibitory effect. QS inhibition downregulated genes related to photosynthesis, membrane synthesis, and oxidative stress and upregulated genes related to MC-LR synthesis. These findings revealed that APS is a pollutant carrier that exacerbates cyanobacterial toxicity and MC-LR release through pollutant adsorption, posing significant ecological risks to aquatic ecosystems.