Influence of zinc oxide nanoparticles (ZnO NPs) on the hemocyte count and hemocyte-mediated immune responses of the Greater Wax Moth Galleria mellonella (Lepidoptera: Pyralidae)

Abstract

In this study, we examined the effects of different doses (100, 500, 1000, 3000, and 5000 ppm) of zinc oxide nanoparticles (ZnO NPs) on the total hemocyte count and hemocyte-mediated immune responses of the Greater Wax Moth Galleria mellonella (Lepidoptera: Pyralidae). The results showed that NPs caused a decrease in hemocyte count at 1000, 3000, and 5000 ppm doses. To investigate the effects of ZnO NPs on the encapsulation and melanization response of G. mellonella, the pre-dyed Sephadex chromatography beads were injected into the hemolymph of each last-instar larva. Larvae were dissected in the 4th and 24th hours after the injection. The level of the encapsulation response and melanization status around the beads were determined under microscopy. The analyses of the beads injected into the insects as encapsulation targets revealed that the number of weakly encapsulated beads increased significantly at 100, 1000, 3000, and 5000 ppm doses when compared to the control group after a short (4-h) post-injection. The number of melanized beads increased significantly at 100, 1000, and 3000 ppm doses in comparison to the control group after the short (4-h) post-injection. Finally, the number of melanized beads decreased significantly at 1000 and 5000 ppm doses when compared to the control group after the long-term (24-h) post-injection.