Optimization of the sublethal dose of silver nanoparticle through evaluating its effect on intestinal physiology of Nile tilapia (Oreochromis niloticus L.)

Silver nanoparticles (SNPs) are widely used in a variety of biomedical and consumer products as an antimicrobial additive. The
present study was conducted to evaluate the impacts of low-dose SNPs on intestinal physiology of tilapia (Oreochromis niloticus L.)
for assessing its apparent environmental risk due to extensive commercial use. SNPs were synthesized by a chemical reduction
method yielding 1–27 nm oval shaped particles. Early fingerlings of tilapia were exposed with two sublethal concentrations (0.8 and
0.4 mg L¡1) of SNPs for twenty one days period and its impact on the intestinal physiology was evaluated by histochemistry,
catalase expression, glutamate dehydrogenase activity, SDS-PAGE and gut micro flora count. Histological analysis showed thinning
of intestinal wall, swelling on mucosal layer and immunohistochemical assay exhibited an enhanced catalase expression in SNPs
treated fishes. Gut microflora count elicited a dose-dependent depletion and a variable SDS-PAGE profile followed by significant
(P < 0.05) elevations in glutamate dehydrogenase activity in SNPs-treated fishes. This study was designed to provide a better
understanding of environmentally acceptable, dose-dependent SNPs delivery in fishes and to formulate guidelines in aquatic
toxicology.