Date Published: June 21, 2019
Publisher: Public Library of Science
Author(s): Laura Abariute, Mercy Lard, Elke Hebisch, Christelle N. Prinz, Etienne Dague.
Semiconductor nanowires are increasingly used in optoelectronic devices. However, their effects on human health have not been assessed fully. Here, we investigate the effects of gallium phosphide nanowires on human lung adenocarcinoma cells. Four different geometries of nanowires were suspended in the cell culture for 48 hours. We show that cells internalize the nanowires and that the nanowires have no effect on cell proliferation rate, motility, viability and intracellular ROS levels. By blocking specific internalization pathways, we demonstrate that the nanowire uptake is the result of a combination of processes, requiring dynamin and actin polymerization, which suggests an internalization through macropinocytosis and phagocytosis.
The use of nanoscaled components in semiconductor technology enabled a substantial improvement in electronic device performance. For instance, III-V semiconductor nanowires are high aspect ratio nanostructures that have been studied extensively and that are considered a promising material for developing optoelectronic devices . Better efficiency light emitting diodes and solar cells have been produced using III-V nanowires [3,4]. The advantages of using nanowires come from the possibility to fabricate highly controlled single crystalline materials with tunable geometry and crystalline structure [5–7]. There is a growing concern about possible nanowire exposure and its impact on human health and the environment. The main focus of concern being nanowire geometry, which resembles that of asbestos fibers and carbon nanotubes. Most of the current research has been concentrated on nanowire arrays and their interactions with living cells [8–13], as well as their applications in biosensing and drug delivery [14–20]. There are only a handful of studies on the effects of substrate-free semiconductor nanowires on biological tissue and ecosystems. In vitro exposure of rat alveolar macrophages to silicon (SiNW) nanowires showed no significant increase in reactive oxygen species levels . In vivo exposure to SiNW via instillation in rats showed a transient dose-dependent increase of lung injury and inflammation. In two studies of gallium phosphide (GaP) and gallium indium phosphide (GaInP) nanowires [23,24], we have found that nanowire exposure through ingestion do not have any detrimental effects on viability and tissue function in Daphnia magna and Drosophila melanogaster [25,26]. Although, few studies present any adverse effects of semiconductor nanowires, we have shown that 5 μm and 10 μm nanowires injected in the rat brain induce a sustained tissue inflammation even one year after the injection [27,28]. Therefore, more studies are necessary to complete the knowledge on the safety of semiconductor nanowires. To date, there are no available commercial products containing nanowires since their synthesis suffers from low throughput and is expensive . However, new technologies, such as aerotaxy, will enable large scale production of III-V nanowires, such as GaP nanowires, in the near future . Integrated in an optoelectronic device such as a solar cell or a LED, these III-V nanowires would be coated with a thin oxide layer for passivation . Therefore, there is a need for investigating the effects of oxide-coated III-V nanowires on cells, and their cellular internalization.
In summary, we have suspended nanowires in the cell medium of cultured A549 cells and investigated the fate of the nanowires and their effects on cell properties. Our results show that nanowires are engulfed by the cells and end up, for the most part, in the cell perinuclear region. The intracellular presence of nanowires does not affect the cell viability, proliferation and motility. The nanowires are internalized through processes requiring dynamin and actin polymerization, suggesting that phagocytosis and macropinocytosis are involved. In our study, nanowires were not found surrounded by macropinosomes or lysosomes, however, this needs to be further confirmed by additional studies. An early nanowire escape from cellular compartments would open for the possibility to use nanowires for cellular transfection, for which early endosome escape is a prerequisite to a successful transfection.