Ingestion of gallium phosphide nanowires has no adverse effect on Drosophila tissue function

Our plain-English summary of Ingestion of gallium phosphide nanowires has no adverse effect on Drosophila tissue function, by K. Adolfsson, M. Schneider, G. Hammarin, et al (Nanotechnology, 2013).

The study

• Authors: K. Adolfsson, M. Schneider, G. Hammarin, U. Häcker, C.N. Prinz
• Journal: Nanotechnology
• Published: 2013;24(28):285101
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Engineered nanoparticles have been under increasing scrutiny in recent years. High aspect ratio nanoparticles such as carbon nanotubes and nanowires have raised safety concerns due to their geometrical similarity to asbestos fibers. III-V epitaxial semiconductor nanowires are expected to be utilized in devices such as LEDs and solar cells and will thus be available to the public. In addition, clean-room staff fabricating and characterizing the nanowires are at risk of exposure, emphasizing the importance of investigating their possible toxicity. Here we investigated the effects of gallium phosphide nanowires on the fruit fly Drosophila melanogaster. Drosophila larvae and/or adults were exposed to gallium phosphide nanowires by ingestion with food. The toxicity and tissue interaction of the nanowires was evaluated by investigating tissue distribution, activation of immune response, genome-wide gene expression, life span, fecundity and somatic mutation rates. Our results show that gallium phosphide nanowires applied through the diet are not taken up into Drosophila tissues, do not elicit a measurable immune response or changes in genome-wide gene expression and do not significantly affect life span or somatic mutation rate.

In plain English

In a laboratory experiment, the authors fed gallium phosphide nanowires to fruit flies (Drosophila melanogaster). They noted that such nanowires raise safety concerns because their shape resembles asbestos fibers. No asbestos was tested. Larvae and adults ate food containing nanowires about 4 µm long and 80 nm wide on average, and some received nanowires coated with hafnium oxide. The authors did not see nanowires cross the gut wall into internal larval tissues. Counts of crystal cells, a type of immune blood cell, did not differ significantly between nanowire-fed and control larvae, while larvae fed E. coli bacteria had significantly more. Gene activity showed no significant changes, and life span was not adversely affected. Egg-laying was slightly lower only on day 29, in flies fed coated nanowires, and the authors said they could not conclude this was an effect. The proportion of flies with tumors, a marker of mutation, was 0.035 for controls, 0.047 for nanowire-fed flies and 0.38 for X-ray-irradiated flies. The nanowire-fed and control groups did not differ significantly. The authors concluded the fly gut seemed relatively insensitive to nanowire exposure. They said they could not exclude effects at higher concentrations.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: animal experiment (laboratory study in fruit flies)
• Who was studied: Wild type fruit flies (Drosophila melanogaster, Oregon R strain), studied as larvae and adults. Longevity vials held 15 males and 15 females each, with three replicates per group. The gene expression study used 5 plates per group. The mutation test scored 300 nanowire-fed flies, 384 control flies and 118 positive control flies. The authors are based at Lund University, Sweden.
• Exposure: Gallium phosphide (GaP) nanowires, length centered around 4 µm and average diameter 80 nm, mixed into the food. Some flies received GaP nanowires coated with a 10 nm layer of hafnium oxide. Larval food contained 10 nanowires per nanolitre. Adult food surfaces held 3 × 10^6 nanowires per square centimetre. No asbestos was tested.
• Main results:
  • The authors did not observe nanowires penetrating the intestinal lining or being taken up into internal larval tissues.
  • Crystal cell (immune cell) counts did not differ significantly between nanowire-exposed larvae and negative controls.
  • Larvae fed E. coli (positive control) had significantly more crystal cells than negative controls and nanowire-exposed larvae (p less than 0.001).
  • No significant difference in gene expression (q less than 5%) was found between nanowire-fed and control larvae.
  • Nanowire ingestion did not adversely affect fly life span, whether flies were exposed as larvae only or throughout adult life.
  • Egg-laying did not differ significantly between groups, except at day 29. On that day flies exposed to hafnium oxide-coated nanowires laid slightly fewer eggs (p less than 0.05).
  • The authors stated they could not conclude that hafnium oxide-coated nanowires affected fecundity.
  • The mutational frequency (proportion of flies with tumors) was 0.035 for control flies (384 flies scored), 0.047 for nanowire-fed flies (300 flies scored) and 0.38 for X-ray-irradiated positive control flies (118 flies scored).
  • No significant difference in mutational frequency was detected between nanowire-fed flies and negative controls.
  • The authors calculated that the concentration used, extrapolated to average human body mass, corresponds to 50 mg of nanowires per day.
• The authors' conclusion: The authors concluded that their results suggest the fruit fly intestinal tract is relatively insensitive to nanowire exposure and protects the adjoining tissues well.
• Limitations the authors state:
  • The authors could not exclude a response at higher nanowire concentrations.
  • The authors suggested that a membrane lining the fly gut (the peritrophic membrane) may have kept nanowires from directly contacting intestinal cells.

Topics

Medical terms in this study, explained in our Lexicon: Aspect Ratio (Length-to-diameter ratio), Somatic Mutation.

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