Acute toxicity evaluation of zinc oxide-low molecular weight chitosan nanocomposites in zebrafish embryo

• The acute embryotoxicity assessment of ZnO and ZnO-LMWCH nanocomposites in zebrafish embryos • The significant reduction in morphological abnormalities and cardiac toxicity following chitosan functionalization • The protective role of low molecular weight chitosan derived from Sepia brevimana in mitigating ZnO-induced developmental toxicity • The enhanced biocompatibility of ZnO-LMWCH nanocomposites for environmental and biomedical applications This study presents the first comprehensive toxicological evaluation of Sepia brevimana -derived low molecular weight chitosan (LMWCH) functionalized zinc oxide nanocomposites in zebrafish ( Danio rerio ) embryos. Uncoated ZnO and LMWCH -coated ZnO nanocomposites were assessed at concentrations of 1–8 µg/mL across 24, 48, and 72 h post-fertilization. Uncoated ZnO induced severe dose-dependent embryotoxicity, including yolk sac edema, spinal deformities, reduced body curvature, and significantly decreased cardiac function. In contrast, chitosan-coated ZnO nanocomposites demonstrated significantly ( P