Green Synthesis of Cymodocea serrulata Zinc Oxide Nanoparticles for Sustainable Antibacterial, and Mosquito Control and their Toxicity to non-target Organisms.

Mosquito-borne diseases such as dengue, malaria, and filariasis have become serious global health concerns due to their contagious nature and widespread prevalence. In this study, ZnO NPs biosynthesized using the seagrass extract of Cymodocea serrulata (CS-ZnO NPs) were prepared from the leaf part and evaluated for their toxicity potential against the larvae, pupae, and adults of various mosquito species, including Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi. The CS-ZnO NPs were characterized using UV-Vis spectroscopy, XRD, FTIR, FE-SEM, EDX, and zeta potential analyses. The CS-ZnO NPs demonstrated significant antibacterial activity against tested bacterial strains: Pseudomonas otitidis (22 ± 0.81 mm), Enterococcus faecalis (18.66 ± 0.47 mm), Bacillus subtilis (14 ± 0.81 mm), and Serratia marcescens (9.66 ± 0.47 mm). Among the mosquito species tested, A. stephensi exhibited the most effective toxicity response. The ovicidal activity of CS-ZnO NPs against A. stephensi showed 12% egg hatchability at a concentration of 100 µg/mL. Furthermore, the larvicidal efficacy of CS-ZnO NPs against A. stephensi displayed strong lethal effects, with LC50 and LC90 values (in µg/mL) recorded as follows: 2.79 and 72.86 for the first instar, 5.89 and 209.93 for the second instar, 7.38 and 328.43 for the third instar, 9.56 and 435.36 for the fourth instar larvae; 8.18 and 357.68 for pupae; and 4.51 and 238.96 for adults. Biosafety assessments were conducted on Danio rerio embryos and Artemia salina nauplii to confirm the non-toxic nature of CS-ZnO NPs. Overall, C. serrulata-synthesized CS-ZnO NPs present a promising, eco-friendly alternative for controlling mosquitoes and eradicating deadly mosquito-borne diseases such as filariasis, dengue, and malaria.