Bioavailability, Toxicity and Biotransformation of Selenium in Midge (Chironomus dilutus) Larvae Exposed via Water or Diet to Elemental Selenium Particles, Selenite, or Selenized Algae

Abstract

Elemental selenium (Se) is generally considered to be biologically inert due to its insolubility in water. It is a common form of Se in sediment near uranium mining and milling operations in northern Saskatchewan, Canada. Nanosized particles of many materials exhibit different properties compared with their bulk phases, in some cases posing health and ecological risks. Here we investigated the bioavailability and toxicity of Se nanoparticles (SeNPs) using 10-day waterborne and dietary exposures to larvae of Chironomus dilutus, a common benthic invertebrate. For comparison, larvae were also exposed to waterborne dissolved selenite and to dietary selenomethionine as selenized algae. Larval Se accumulation was evaluated using graphite furnace atomic absorption spectroscopy or inductively coupled plasma mass spectroscopy for total Se and X-ray absorption spectroscopy for Se chemical speciation. Exposure to nanoparticulate Se resulted in Se bioaccumulation, at high concentrations, inhibiting larval growth in both waterborne and dietary exposures; larvae predominantly accumulated selenomethionine-like species regardless of uptake route or form of Se tested. Despite the observed Se accumulation, our findings suggest there is little risk of direct SeNP toxicity to benthic invertebrates in Se-contaminated sediments in northern Saskatchewan. Nevertheless, elemental Se in sediments may be biologically available and may contribute directly or indirectly to the risk of Se toxicity to egg-laying vertebrates (fish and piscivorous birds) in Se-contaminated aquatic systems. It thus may be necessary to include elemental Se as a source of potential Se exposure in ecological risk assessments.

Selenium Nanoparticle Synthesized by Proteus mirabilis YC801: An Efficacious Pathway for Selenite Biotransformation and Detoxification

“…Among them, selenite (SeO 3 2− ) and selenate (SeO 4 2− ) show the greatest biotoxic effects due to their high solubilities and bioavailabilities. Elemental selenium (Se 0 ) is the least mobile form and cannot readily be used by biological systems; Se 0 is generally considered biologically inert and safe for terrestrial and aquatic environments in low amounts [10]. Therefore, biogeochemical cycles that involve the reduction of selenite/selenate to Se 0 are of paramount importance and have attracted worldwide attention [9,11].…”

Integrative assessment of selenium speciation, biogeochemistry, and distribution in a northern coldwater ecosystem

“…Although elemental Se is generally believed to be insoluble and nonbioavailable, the exact form and stability of this Se is unknown. Exposure of chironomids to synthetically‐produced red elemental Se nanoparticles (SeNPs) results in accumulation of Se in chironomid larvae (Gallego‐Gallegos et al ). The mechanism of this process is presently unknown, but could include the oxidation of SeNPs into selenite in the exposure solution and/or in the gut of the chironomid larvae, both of which may be microbially‐mediated.…”

Effect of chitosan with different molecular weight on the stability, antioxidant and anticancer activities of well‐dispersed selenium nanoparticles

“…The dose and form of selenium are the determining factors related to its biological activity, toxicity and cancer prevention [5]. SeNPs are novel selenium species with unique biological, appearing to be more effective than other forms of selenium at increasing selenoproteins expression, scavenging free radicals, and preventing oxidative DNA damage as antioxidant [6,7]. SeNPs also have additional benefits such as low toxicity and acceptable bioavailability, which have aroused widespread attention in recent years [8][9][10].…”