Neurotoxicity of Carboxyl-Modified Polystyrene Microplastics on Zebrafish at Early Developmental Stage

• • PS-COOH exposure at 10 μg·L−1 significantly decreased tail coiling frequency at 24 hpf and average swimming speed at 120 hpf compared to PS (P<0.05), indicating enhanced neurobehavioral toxicity due to carboxyl modification. • • PS-COOH at 10 μg·L−1 disrupted neurotransmitter balance, altering levels of acetylcholine (ACh), serotonin (5-HT), and γ-aminobutyric acid (GABA), which are critical for synaptic transmission and neuronal function. • • Transgenic zebrafish Tg(huc:EGFP) fluorescence experiments showed that PS-COOH concentrations ranging from 0.1 to 100 μg·L−1 caused structural damage to central neurons, confirming neurocytotoxicity at environmentally relevant levels. • • The study establishes a dose-response relationship for PS-COOH neurotoxicity, with significant effects observed at concentrations as low as 0.1 μg·L−1, underscoring the potential ecological risk of modified microplastics in aquatic environments.