Determination of the acute toxic effects of zinc oxide nanoparticles (ZnO NPs) in total hemocytes counts of Galleria mellonella (Lepidoptera: Pyralidae) with two different methods

Emerging trends to replace pesticides with nanomaterials: Recent experiences and future perspectives for ecofriendly environment

Despite the widespread usage to safeguard crops and manage pests, pesticides have detrimental effects on the environment and human health. The necessity to find sustainable agricultural techniques and meet the growing demand for food production has spurred the quest for pesticide substitutes other than traditional ones. The unique qualities of nanotechnology, including its high surface area-to-volume ratio, controlled release, and better stability, have made it a promising choice for pest management. Over the past ten years, there has been a noticeable growth in the usage of nanomaterials for pest management; however, concerns about their possible effects on the environment and human health have also surfaced. The purpose of this review paper is to give a broad overview of the worldwide trends and environmental effects of using nanomaterials in place of pesticides. The various types of nanomaterials, their characteristics, and their possible application in crop protection are covered. The limits of the current regulatory frameworks for nanomaterials in agriculture are further highlighted in this review. Additionally, it describes how standard testing procedures must be followed to assess the effects of nanomaterials on the environment and human health before their commercialization. In order to establish sustainable and secure nanotechnology-based pest control techniques, the review concludes by highlighting the significance of taking into account the possible hazards and benefits of nanomaterials for pest management and the necessity of an integrated approach. It also emphasizes the importance of more investigation into the behavior and environmental fate of nanomaterials to guarantee their safe and efficient application in agriculture.

Subchronic toxicity of iron-selenium nanoparticles on oxidative stress response, histopathological, and nuclear damage in amphibian larvae Rana saharica

In this work, we evaluated the subchronic toxicity of FeSe nanoparticles (NPs) in tadpoles of Rana saharica. Tadpoles were exposed for 1-3 weeks to FeSe NPs at 5 mg/L and 100 mg/L rates. Parameters of oxidative stress were measured in whole larvae, and the micronucleus test was performed on circulating blood erythrocytes. We noted a disturbance of the detoxification systems. Enzymatic and non-enzymatic data showed that exposure to FeSe NPs involved a highly significant depletion of GSH, a significant increase in GST activity, and a lipid peroxidation associated with a highly significant increase in MDA. We also noted a neurotoxic effect characterized by a significant inhibition of AChE activity. A micronucleus test showed concentration-dependent DNA damage. This research reveals that these trace elements, in their nanoform, can cause significant neurotoxicity, histopathologic degeneration, cellular and metabolic activity, and genotoxic consequences in Rana larvae.

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)

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.

Antibacterial Activity of ZnO Nanoparticles in a Staphylococcus-aureus-Infected Galleria mellonella Model Is Tuned by Different Apple-Derived Phytocargos

This research investigates pH changes during the green synthesis of ZnO nanoparticles (NPs) and emphasises its importance in their physicochemical, antibacterial, and biological properties. Varying the synthesis pH from 8 to 12 using "Bravo de Esmolfe" apple extracts neither affected the morphology nor crystallinity of ZnO but impacted NP phytochemical loads. This difference is because alkaline hydrolysis of phytochemicals occurred with increasing pH, resulting in BE-ZnO with distinct phytocargos. To determine the toxicity of BE-ZnO NPs, Galleria mellonella was used as an alternative to non-rodent models. These assays showed no adverse effects on larvae up to a concentration of 200 mg/kg and that NPs excess was relieved by faeces and silk fibres. This was evaluated by utilising fluorescence-lifetime imaging microscopy (FLIM) to track NPs' intrinsic fluorescence. The antibacterial efficacy against Staphylococcus aureus was higher for BE-ZnO12 than for BE-ZnO8; however, a different trend was attained in an in vivo infection model. This result may be related to NPs' residence in larvae haemocytes, modulated by their phytocargos. This research demonstrates, for the first time, the potential of green synthesis to modulate the biosafety and antibacterial activity of NPs in an advanced G. mellonella infection model. These findings support future strategies to overcome antimicrobial resistance by utilizing distinct phytocargos to modulate NPs' action over time.

Zinc Oxide Nanoparticles Prime a Protective Immune Response in Galleria mellonella to Defend Against Candida albicans

Purpose: Zinc oxide nanoparticles (ZnO-NPs) have exerted antimicrobial properties. However, there is insufficient evaluation regarding the in vivo antifungal activity of ZnO-NPs. This study aimed to investigate the efficacy and mechanism of ZnO-NPs in controlling Candida albicans in the invertebrate Galleria mellonella. Methods: Galleria mellonella larvae were injected with different doses of ZnO-NPs to determine their in vivo toxicity. Non-toxic doses of ZnO-NPs were chosen for prophylactic injection in G. mellonella followed by C. albicans infection. Then the direct in vitro antifungal effect of ZnO-NPs against C. albicans was evaluated. In addition, the mode of action of ZnO-NPs was assessed in larvae through different assays: quantification of hemocyte density, morphology observation of hemocytes, characterization of hemocyte aggregation and phagocytosis, and measurement of hemolymph phenoloxidase (PO) activity. Results: Zinc oxide nanoparticles were non-toxic to the larvae at relatively low concentrations (≤20 mg/kg). ZnO-NP pretreatment significantly prolonged the survival of C. albicans-infected larvae and decreased the fungal dissemination and burden in the C. albicans-infected larvae. This observation was more related to the activation of host defense rather than their fungicidal capacities. Specifically, ZnO-NP treatment increased hemocyte density, promoted hemocyte aggregation, enhanced hemocyte phagocytosis, and activated PO activity in larvae. Conclusion: Prophylactic treatment with lower concentrations of ZnO-NPs protects G. mellonella from C. albicans infection. The innate immune response primed by ZnO-NPs may be part of the reason for the protective effects. This study provides new evidence of the capacity of ZnO-NPs in enhancing host immunity and predicts that ZnO-NPs will be attractive for further anti-infection applications.

Effects of Copper Oxide Nanoparticles on Immune and Metabolic Parameters of Galleria mellonella L

In this study, the effects of dietary CuO nanoparticles (NPs) on metabolic enzyme activity, biochemical parameters, and total (THC) and differential hemocyte counts (DHC) were determined in Galleria mellonella larvae. Using concentrations of 10, 100, 1000 mg/L and the LC10 and LC30 levels of CuO NPs, we determined that the NPs negatively impacted metabolic enzyme activity and biochemical parameters in larval hemolymph. Compared with the control, the greatest increase in THC was observed in larvae fed on diets with 100 mg L^-1 of CuO NPs. Plasmatocytes and granulocytes were among the most numerous hemocytes in all treatments. These results suggest that dietary CuO NPs effects the metabolic metabolism and immune system of G. mellonella and provide indirect information regarding the toxic effects of CuO NPs in mammalian immune system given similarities between mammalian blood cells and insect hemocytes.

Copper and zinc impact on stress biomarkers and growth parameters in a model organism, Galleria mellonella larvae

The objective of the present study was to investigate the impact of zinc and copper on some biomarkers in a model organism Galleria mellonella L. We investigated the effects of Cu and Zn (10, 50, and 100 mg/100 g diets) on different biomarkers such as oxidative stress parameters (SOD and CAT activities and MDA levels), energy resources (protein, lipid and glycogen levels), electrolyte contents (Ca, Na, and K levels), total hemocyte count (THC), and growth and development of G. mellonella. Additionally, the accumulation levels of the used metals were also studied. Cu caused a significant decrease in protein, lipid and glycogen levels. SOD and CAT activities significantly increased at all concentrations of Cu, while they significantly increased at only high concentrations of Zn (50 and 100 mg). Lipid peroxidation levels (MDA) significantly elevated at high concentrations of both metals. It was determined that the Cu and Zn accumulation increased depending on the increase of the concentration. Zn caused an alteration in Ca level at the concentrations of 50 and 100 mg, and K and Na levels at all concentrations. While, THC significantly reduced at all Cu concentrations, this reduction was observed only at higher Zn concentrations (50 and 100 mg). Larval and pupal development time significantly extended at the highest concentration (100 mg) of Cu, and females' lifespan significantly shortened at all concentrations of Cu. Zinc caused an extension in larval development time at the highest concentration (100 mg), and caused a shortening in females and males' lifetime at all concentrations. The observed changes in biomarkers can be used as the illustration of potential toxic effects of high levels of Cu and Zn in organisms.

Influence of titanium dioxide nanoparticles on bioaccumulation, antioxidant defense and immune system of Galleria mellonella L

Nanomaterials of different sizes and diameters are frequently used in various industrial areas, due to the rapid development of nanotechnology. Hence, it leads to toxic effects on the environment and non-target organisms, and adverse effects such as oxidative stress and membrane damage in cells and tissues are occurred. Some biomarkers such as the accumulation of intermediate products, detoxification of the immune system, or xenobiotic are used in the detection of toxic effects of exogenous substances in living organisms. In this study, the effects on catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione-s-transferase (GST) enzyme activities to determine the toxic effects of TiO₂ NPs on antioxidant defense system, acetylcholinesterase (AChE) activity to determine their neurotoxic effects, and total hemocyte count (THC) to determine their effect on the immune system were investigated in model organism Galleria mellonella larvae. It was determined that major amounts of Ti were mostly eliminated through the Malpighian tubules. Moreover, TiO₂ NPs in different concentrations caused the formation of reactive oxygen species in G. mellonella and lead to an increase in antioxidant enzymes. Decreases were found in THC due to the TiO₂ NP application. As a result, it was concluded that TiO₂ NPs caused accumulation in tissues of the model organism G. mellonella, resulting in oxidative stress and has adverse effects on the immune system.

Effects of the copper oxide nanoparticles (CuO NPs) on Galleria mellonella hemocytes

In this study, 38 nm-sized and flake-like-shaped CuO NPs (10, 50, 100, 150 μg/10 µl/larva) were force-fed to fourth instar (100 ± 20 mg) Galleria mellonella (Lepidoptera: Pyralidae) larvae under the laboratory conditions. The effects of CuO NPs on total hemocyte counts (THCs) and the frequency of viable, mitotic, apoptotic, necrotic, and micronucleated hemocyte indices were detected with the double-staining protocol by hematoxylin and eosin (H&E) stains. The total hemocyte counts (THCs) did not change significantly in G. mellonella larvae at all concentrations for 24 h and 72 h post-force-feeding treatment. The ratio of viable hemocytes decreased at 50, 100, 150 μg/10 µl concentrations in 24 h and 72 h when compared with untreated larvae. The increases in the percentage of mitotic and micronucleated hemocytes were statistically significant at 150 μg/10 µl in 24 h. The results showed that high concentrations (>10 μg/10 µl) of CuO NPs increased the percentage of apoptotic hemocytes in 24 h. 100 and 150 μg/10 µl of CuO NPs caused a significant increase in the percentage of necrotic hemocytes in 24 h. The decrease in the percentage of mitotic hemocytes at 10, 100 and 150 μg/10 µl in 72 h was statistically significant. Apoptotic hemocytes increased and were found to be higher at 100 and 150 μg/10 µl of CuO NPs in 72 h in comparison with the untreated larvae. Finally, we observed an increase in the percentage of necrotic hemocytes at 150 μg/10 µl in 72 h.

Utility of Galleria mellonella larvae for evaluating nanoparticle toxicology

The use of nanoparticles in consumer products is currently on the rise, so it is important to have reliable methods to predict any associated toxicity effects. Traditional in vitro assays fail to mimic true physiological responses of living organisms against nanoparticles whereas murine in vivo models are costly and ethically controversial. For these reasons, this study aimed to evaluate the efficacy of Galleria mellonella as an alternative, non-rodent in vivo model for examining nanoparticle toxicity. Silver, selenium, and functionalized gold nanoparticles were synthesized, and their toxicity was assessed in G. mellonella larvae. The degree of acute toxicity effects caused by each type of NP was efficiently detected by an array of indicators within the larvae: LD₅₀ calculation, hemocyte proliferation, NP distribution, behavioral changes, and histological alterations. G. mellonella larvae are proposed as a nanotoxicological model that can be used as a bridge between in vitro and in vivo murine assays in order to obtain better predictions of NP toxicity.