Mechanism of Silver Nanoparticles Action on Insect Pigmentation Reveals Intervention of Copper Homeostasis

Abstract

Silver nanoparticles (AgNPs), like almost all nanoparticles, are potentially toxic beyond a certain concentration because the survival of the organism is compromised due to scores of pathophysiological abnormalities past that concentration. However, the mechanism of AgNP toxicity remains undetermined. Instead of applying a toxic dose, we attempted to monitor the effects of AgNPs at a nonlethal concentration on wild type Drosophila melanogaster by exposing them throughout their development. All adult flies raised in AgNP doped food showed that up to 50 mg/L concentration AgNP has no negative influence on median survival; however, these flies appeared uniformly lighter in body color due to the loss of melanin pigments in their cuticle. Additionally, fertility and vertical movement ability were compromised due to AgNP feeding. Determination of the amount of free ionic silver (Ag+) led us to claim that the observed biological effects have resulted from the AgNPs and not from Ag+. Biochemical analysis suggests that the activity of copper dependent enzymes, namely tyrosinase and Cu-Zn superoxide dismutase, are decreased significantly following the consumption of AgNPs, despite the constant level of copper present in the tissue. Consequently, we propose a mechanism whereby consumption of excess AgNPs in association with membrane bound copper transporter proteins cause sequestration of copper, thus creating a condition that resembles copper starvation. This model also explains the cuticular demelanization effect resulting from AgNP since tyrosinase activity is essential for melanin biosynthesis. Finally, we claim that Drosophila, an established genetic model system, can be well utilized for further understanding of the biological effects of nanoparticles.

Effect of biopolymer stabilized silver nanoparticles on antioxidant genes from larvae of Anopheles Stephensi mosquito

“…Also, these NPs have been found to up-regulate and down-regulate processes such as toll like receptors 2 (TLR 2), mRNA transcript in macrophages, nucleotide binding oligomerizationprotein 2 (NOD 2), CD40, CD80, CD86, IL-1 receptor associated kinase 3 (IRAK 3) and matrix metallopeptidase 9 (MMP 9) suggesting that AgNPs possessing PVP have wider applications which are yet to be realized apart from the current revelations. Also, Armstrong et al (2013) have established in Drosophila that large uptake of AgNPs in association to membrane bound copper transport proteins cause sequestration of copper, thus creating a condition that resembles copper starvation resulting death.…”

“…Bacteria mortality occurs via formation of reactive oxygen species (ROS), cell membrane damage, interaction with DNA, cell defensins, cytoplasmic disintegrations and mitochondrial malfunctions, which all together compromise physiological normalcy facilitating death. However, these observations have not been proven in mosquitoes, though reports in Drosophila points to copper starvation condition like which causes death [5]. Hence, the current work sort to elucidate the mode action of the bio-polymer stabilized AgNPs for the observed mortality as reported in our previous research [4].…”

Effects of carbon nanofiber on physiology of Drosophila

“…Especially, silver and gold nanoparticles show toxic effects on Drosophila fecundity and lifespan. [21][22][23]29 On the other hand, other studies reported that nanomaterials lack any significant adverse effects on Drosophila. For example, multi-walled carbon nanotubes at a concentration of 1,000 μg/g were shown to have no significant effect on developmental time or egg viability, 31 and single-walled carbon nanotubes at a concentration of 12-24 ppm during larval stage were reported to have no effect on pupal viability.…”

“…Specifically, long-term exposure of D. melanogaster to silver nanoparticles during development has been shown to increase genetic instability related to somatic recombination as well as perturb copper homeostasis, resulting in impaired body pigmentation. 20,21 Short-term exposure of Drosophila larvae to silver nanoparticles is associated with induction of oxidative stress and apoptosis. 15 In addition, long-term exposure to gold nanoparticles (12 μg/g) was reported to reduce lifespan and fertility in flies, 22 depending on nanoparticle concentration rather than size.…”

Effects of microbicide based on lactic acid and metal nanoparticles on laboratory animals

“…The study of microbicidal properties of silver nanoparticles and their use to create new complex disinfectants is a promising area of research in many countries around the world (Lopes et al, 2016;Ivask et al, 2014;De Gusseme et al, 2010). At the same time, in the literature there is enough information on the potential toxicity of both silver nanoparticles and other nanoparticles in certain concentrations not only on pathogenic microorganisms, but also on the body of different species of animals (Ivask et al, 2014;Armstrong et al, 2013;Likus et al, 2013). In addition, nanomaterials are sufficiently dynamic in biological and ecological environments.…”