SUB-CHRONIC DIETARY TOXICITY OF ZINC OXIDE-SILICA NANOPARTICLES IN GRASS CARP (CTENOPHARYNGODON IDELLA): HEMATOLOGICAL, BIOCHEMICAL, AND HISTOPATHOLOGICAL RESPONSES

Abstract

The rapid expansion of nanotechnology and the consequent release of engineered nanoparticles into aquatic ecosystems have raised significant concerns regarding the safety of freshwater biota. The present study evaluated the sub-chronic effects of dietary Zinc Oxide-Silica (ZnO-SiO2) nanoparticles on hematological parameters, serum biochemistry, and tissue architecture of grass carp (Ctenopharyngodon idella) in a 45-day controlled trial. Four experimental groups were established: one control group receiving a basal diet, and three treatment groups (T1, T2, T3) receiving 50, 100, and 200 mg of ZnO-SiO2 nanoparticles per 0.5 kg of feed, respectively. Blood samples collected at the end of the trial were analyzed for hematological indices (WBC, RBC, MCV, MCH, HCT, HGB) and serum biochemical parameters (urea, creatinine, total protein, globulin, albumin, cholesterol). Kidney and intestine tissues were processed for histopathological examination using hematoxylin and eosin staining. One-way ANOVA revealed significant increases in white blood cell count (P < 0.05), accompanied by a selective increase in mean corpuscular hemoglobin and a distinct alteration in hematocrit levels across nanoparticle-treated groups compared with the control. Serum biochemistry showed significant elevations in urea, alongside variable fluctuations in cholesterol, while creatinine and albumin remained statistically unchanged (P > 0.05). Notably, a robust and significant increase in globulin levels was observed across all nanoparticle-treated groups compared with the control (P < 0.05), accompanied by a significant decrease in total protein concentration. Histopathological evaluation demonstrated progressive degenerative and inflammatory changes in kidney (tubular degeneration, glomerular atrophy, inflammatory infiltration, hemorrhage, necrosis) and intestine (villus shortening, epithelial degeneration, inflammatory infiltration, epithelial necrosis, mucosal gland degeneration) in a clear dose-dependent response pattern. These findings indicate that dietary exposure to ZnO-SiO2 nanoparticles induces detectable hematological imbalance, biochemical disturbance, and structural tissue damage in grass carp under sub-chronic conditions, supporting oxidative stress and inflammation as central mechanistic drivers. The results emphasize the need for ecological risk assessment frameworks of nanocomposite release into freshwater aquaculture systems.