Surf Redfish-Based ZnO-NPs and Their Biological Activity with Reference to Their Non-Target Toxicity.

The marine environment is a rich source of bioactive compounds. Therefore, the sea cucumber was isolated from the Red Sea at the Al-Ain Al-Sokhna coast and it was identified as surf redfish ( Actinopyga mauritiana ). The aqueous extract of the surf redfish was utilized as an ecofriendly, novel and sustainable approach to fabricate zinc oxide nanoparticles (ZnO-NPs). The biosynthesized ZnO-NPs were physico-chemically characterized and evaluated for their possible antibacterial and insecticidal activities. Additionally, their safety in the non-target organism model (Nile tilapia fish) was also investigated. ZnO-NPs were spherical with an average size of 24.69 ± 11.61 nm and had a peak at 350 nm as shown by TEM and UV-Vis, respectively. XRD analysis indicated a crystalline phase of ZnO-NPs with an average size of 21.7 nm. The FTIR pattern showed biological residues from the surf redfish extract, highlighting their potential role in the biosynthesis process. DLS indicated a negative zeta potential (-19.2 mV) of the ZnO-NPs which is a good preliminary indicator for their stability. ZnO-NPs showed larvicidal activity against mosquito Culex pipiens (LC 50 = 15.412 ppm and LC 90 = 52.745 ppm) and a potent adulticidal effect to the housefly Musca domestica (LD 50 = 21.132 ppm and LD 90 = 84.930 ppm). Tested concentrations of ZnO-NPs showed strong activity against the 3rd larval instar. Topical assays revealed dose-dependent adulticidal activity against M. domestica after 24 h of treatment with ZnO-NPs. ZnO-NPs presented a wide antibacterial activity against two fish-pathogen bacteria, Pseudomonas aeruginosa and Aeromonas hydrophila . Histopathological and hematological investigations of the non-target organism, Nile tilapia fish exposed to 75-600 ppm ZnO-NPs provide dose-dependent impacts. Overall, data highlighted the potential applications of surf redfish-mediated ZnO-NPs as an effective and safe way to control mosquitoes, houseflies and fish pathogenic bacteria.