Green synthesis of zinc oxide nanoparticles using Caulerpa chemnitzia and evaluation of their effects against methylparaben-induced organ changes in zebrafish

The increasing use of pesticides like methylparaben (MeP) poses significant environmental and health risks, especially in aquatic ecosystems. This study aimed to synthesize ZnO-NPs using Caulerpa chemnitzia extract (C@ZnO-NPs) and evaluate their physicochemical characteristics and therapeutic potential in mitigating MeP-induced oxidative stress, inflammation and behavioral toxicity in zebrafish. ZnO-NPs were synthesized via a green route using C. chemnitzia extract and characterized using UV-Vis spectroscopy, XRD, FTIR, DLS, zeta potential analysis, SEM-EDAX and HR-TEM. Behavioral assays (Light-Dark Test, Novel Tank Test and T-Maze), biochemical analyses (antioxidants, ROS, LPO and ALT), histopathology, western blotting, and qRT-PCR were performed on zebrafish exposed to MeP. UV-Vis (360 nm peak) and XRD confirmed the formation of crystalline C@ZnO NPs. FTIR and EDAX validated functional group involvement and elemental purity. DLS and zeta potential analyses indicated moderate stability. Behavioral impairments due to MeP were dose-dependently reversed by ZnO-NPs, particularly at 40 mg/L. Antioxidant levels were restored, and oxidative stress and ALT levels were reduced. Histological damage in gill and liver tissues improved with treatment. Inflammatory markers (NF-κB and TNF-α) were significantly downregulated. C@ZnO-NPs effectively ameliorated MeP-induced neurotoxicity, oxidative stress and inflammation in zebrafish, highlighting their potential as a green nanotherapeutic agent in environmental toxicology.