Abstract
Engineered nanomaterials (ENMs) are materials with at least one dimension between 1–100 nm. The small size of ENMs results in a large surface area to volume ratio, giving ENMs novel characteristics that are not traditionally exhibited by larger bulk materials. Coupled with large surface area is an enormous capacity for surface functionalization of ENMs, e.g., with different ligands or surface changes, leading to an almost infinite array of variability of ENMs. Here we explore the effects of various shaped (spheres, rods) and charged (negative, positive) gold ENMs on Daphnia magna (D. magna) in terms of survival, ENM uptake and production of reactive oxygen species (ROS), a key factor in oxidative stress responses. We also investigate the effects of gold ENMs binding to the carapace of D. magna and how this may induce moulting inhibition in addition to toxicity and stress. The findings suggest that ENM shape and surface charge play an important role in determining ENM uptake and toxicity.
Highlights
The incorporation of engineered nanomaterials (ENMs) into industrial products has significantly increased due to their enhanced reactivity characteristics, many of which are provided by an increased surface-area-to-volume ratio compared to larger micron or bulk material of the same chemical composition [1,2]
Gold nano-rods are being tested for use in cancer therapy, and are found to have the highest absorption efficiency (~14), which refers to their heating capacity, compared to nano-spheres or silica-gold nano-shells with absorption efficiencies ranging between 3.5–4.02 [6]
All ENMs were characterized in high hardness (HH) Combo medium
Summary
The incorporation of engineered nanomaterials (ENMs) into industrial products has significantly increased due to their enhanced reactivity characteristics, many of which are provided by an increased surface-area-to-volume ratio compared to larger micron or bulk material of the same chemical composition [1,2]. There has been considerable progress towards the incorporation of spherical gold ENMs into medical applications, for example, by using gold ENMs to bind antibodies targeted for cancer cells [6]. Gold ENMs with a high aspect ratio (rods) are better photoabsorbers than spherical gold ENMs, and can convert the absorbed light to localized heath to photothermally destruct cancer cells [7]. Due to the increased use of various shaped gold ENMs in medical research, where the annual estimated consumption of nanoscale gold particles is 540 kg in the United Kingdom, which equals approximately 4.27 × 1020 ENMs assuming ENMs are 50 nm, the predicted environmental concentration (PEC) in surface waters is estimated at 468 pg/L [8] and the deposition of gold ENMs into the environment and their subsequent interaction with organisms is a growing concern
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