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

Abstract

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.

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

“…For all particle concentrations, a survival rate of 100% was observed ( Figure 2 a). This observation agrees with the range of efficacy and non-toxicity reported for non-green-synthesised ZnO NPs in Galleria mellonella [ 11 , 12 ].…”

“…An in vivo study on Helicoverpa armigera larvae revealed the toxicity of green-synthesised ZnO NPs when using neem leaf extracts at doses up to 200 mg/kg [ 9 ]. Multiple in vivo studies on Galleria mellonella larvae have also reported the toxicity of conventionally synthesised ZnO NPs [ 10 , 11 , 12 , 13 ]. Eskin et al [ 11 ] reported pulpal toxicity at concentrations greater than 1000 mg/kg while observing extended adult longevity at concentrations as high as 5000 mg/kg.…”

“…Eskin et al [ 11 ] reported pulpal toxicity at concentrations greater than 1000 mg/kg while observing extended adult longevity at concentrations as high as 5000 mg/kg. Xu et al [ 12 ] reported toxicity above 400 mg/kg for ZnO nanorods (NRs). The uptake of polygonal-shaped ZnO NPs by haemocytes was confirmed, and toxic effects on G. mellonella larvae were observed at levels above 115 mg/kg [ 13 ].…”

“…It is worth noting that pre-treating larvae with low concentrations of non-toxic ZnO NRs (≤20 mg/kg) significantly prolonged the survival of Candida - albicans -infected larvae and reduced fungal dissemination. Furthermore, adult weight increased at 100 mg/kg [ 11 , 12 ], indicating that concentrations in these orders of magnitude offer both antifungal and nutritional benefits. Given their antibacterial properties, ZnO NPs decreased the species richness and diversity of the Bombyx mori gut bacterial community and shifted their configuration to an overt microbiome [ 14 ].…”

Enhanced antimicrobial efficacy of biogenic ZnO nanoparticles through UV-B activation: A novel approach for textile garment

“…In the case of C. albicans , the fungicidal effect of ZnO NPs + UV-B at 1, 2, and 3 min reached 100 % and was statistically significant against the negative control. A previous study using an InVivo model to determine the phagocytic response of G. mellonella after infection by C. albicans used ZnO NP at 0.2 mg/kg, reducing mortality up to 13 % compared to the negative control (p < 0.05), and when used at concentrations of 2 mg/kg all infected larvae survived, also demonstrating good tolerance to the concentrations tested [ 58 ]. This demonstrates the effectiveness of ZnO nanoparticles and the tolerance of eukaryotic cells to these nanoparticles.…”