Green synthesis of metallic nanoparticles is a promising way of preparing nanoparticles using plant extracts that have lesser toxicity in any organisms. In the present work, we analyzed the antibacterial activity of Calotropis gigantea (ZnO) and (Cu) mediated nanoparticles in an in vitro assay against S. aureus, E. faecalis, K. pneumoniae and E. coli. Where, against Aeromonas hydrophila (A. hydrophila) in an in vivo assay employing Labeo rohita (L. rohita). L. rohita were divided into seven groups for both (ZnO) and (Cu) nanoparticles respectively: Control, A. hydrophila infected, Cu NPs (75 µg/L), ZnO NPs (75 µg/L), Cu NPs+I (75 µg/L) and ZnO NPs+I (75 µg/L) fish treated groups. Change in different bio-indicators such as hematological, histological and enzyme analysis were observed. Interestingly, the infected fish treated with both types of ZnO NPs and Cu NPs exhibited a higher survival rate than the untreated infected fish and demonstrated signs of recovery from infection, providing a compelling indication of the positive impact of photosynthesized ZnO NPs and Cu NPs. Disruptions in hematological and histological parameters were found in the infected fish. Both ZnO NPs and Cu NPs showed recovery on the hematological and histological parameters. Analysis of oxidative stress also revealed provoking evidence of the positive impact of ZnO and Cu NPs treatment against disease progression in the infected fish. The major finding of the study was that the higher concentrations of the nanoparticles (75 µg/L in the case of ZnO NPs and 75 µg/L in the case of Cu NPs) were more effective in fighting against disease. In conclusion, our work presents novel insights for the use of green-synthesized ZnO and Cu NPs as economic and innocuous antibacterial candidates in aquaculture.

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Index Terms- Znic Oxide, Nanoparticles, Calotropis gigantean, Labeo rohita, Aeromonas