Cellular internalization and stress response of ingested amorphous silica nanoparticles in the midgut of Drosophila melanogaster

BackgroundAmorphous silica nanoparticles (aSNPs) are used for various applications including food industry. However, limited in vivo studies are available on absorption/internalization of ingested aSNPs in the midgut cells of an organism. The study aims to examine cellular uptake of aSNPs (< 30 nm) in the midgut of Drosophila melanogaster (Oregon R+) owing to similarities between the midgut tissue of this organism and human and subsequently cellular stress response generated by these nanoparticles.MethodsThird instar larvae of D. melanogaster were exposed orally to 1–100 μg/mL of aSNPs for 12–36 h and oxidative stress (OS), heat shock genes (hsgs), membrane destabilization (Acridine orange/Ethidium Bromide staining), cellular internalization (TEM) and apoptosis endpoints.ResultsA significant increase was observed in OS endpoints in the midgut cells of exposed Drosophila in a concentration- and time-dependent manner. Significantly increased expression of hsp70 and hsp22 along with caspases activation, membrane destabilization and mitochondrial membrane potential loss was also observed. TEM analysis showed aSNPs-uptake in the midgut cells of exposed Drosophila via endocytic vesicles and by direct membrane penetration.ConclusionaSNPs after their internalization in the midgut cells of exposed Drosophila larvae show membrane destabilization along with increased cellular stress and cell death.General significanceIngested aSNPs show adverse effects on the cells of GI tract of the exposed organism thus their industrial use as a food-additive may raise concern to human health.

► Cellular internalization of ingested aSNPs by endocytosis and direct penetration
► aSNPs mediated membrane destabilization in the midgut cells of Drosophila.
► aSNPs increased ROS generation and evoked oxidative stress in midgut cells.
► aSNPs induced heat shock genes (hsp70, hsp22) in midgut cells.
► aSNPs induced mitochondrial membrane potential loss and apoptosis in midgut cells.