Intracellular Uptake: A Possible Mechanism for Silver Engineered Nanoparticle Toxicity to a Freshwater Alga Ochromonas danica

Abstract

The behavior and toxicity of silver engineered nanoparticles (Ag-ENs) to the mixotrophic freshwater alga Ochromonas danica were examined in the present study to determine whether any other mechanisms are involved in their algal toxicity besides Ag+ liberation outside the cells. Despite their good dispersability, the Ag-ENs were found to continuously aggregate and dissolve rapidly. When the initial nanoparticle concentration was lower than 10 µM, the total dissolved Ag+ concentration ([Ag+]T) in the suspending media reached its maximum after 1 d and then decreased suggesting that Ag+ release might be limited by the nanoparticle surface area under these conditions. Furthermore, Ag-EN dissolution extent remarkably increased in the presence of glutathione. In the Ag-EN toxicity experiment, glutathione was also used to eliminate the indirect effects of Ag+ that was released. However, remarkable toxicity was still observed although the free Ag+ concentration in the media was orders of magnitude lower than the non-observed effect concentration of Ag+ itself. Such inhibitive effects were mitigated when more glutathione was added, but could never be completely eliminated. Most importantly, we demonstrate, for the first time, that Ag-ENs can be taken in and accumulated inside the algal cells, where they exerted their toxic effects. Therefore, nanoparticle internalization may be an alternative pathway through which algal growth can be influenced.

Toxicity, bioaccumulation and biomagnification of silver nanoparticles in green algae (Chlorellasp.), water flea (Moina macrocopa), blood worm (Chironomusspp.) and silver barb (Barbonymus gonionotus)

“…The accumulation of Ag + and AgNPs in plankton was probably due to their attachment to the cell surface of organisms or perhaps entering the cells directly (Miao et al, 2010). The accumulation of silver nanoparticles in zooplankton could be the result of absorption around carapaces since they are chitins and can absorb ions (Benguela and Benaissa, 2002).…”

Transformations of silver nanoparticles in wastewater effluents: links to Ag bioavailability

“…Ag NPs have been shown to undergo physical and chemical transformations when they end up in the environment [17]. Depending on which environmental compartment (e.g., soil, wastewater, and surface water) they end up in, the type and extent of the physicochemical transformation will be different.…”

“…I, pH, presence of ligands, temperature)-the particles may be subject to agglomeration/aggregation, dispersion or dissolution, which will change the particle size [17].…”

“…There are a variety of coatings used for Ag NPs to stabilize them against agglomeration, including citrate, carbonate, polyvinylpyrrolidine, polyacrylate and polyvinylamide [17,31].…”

Antibacterial Activity of Cetyltrimethylammonium Bromide Modified Silver-Bentonite

“…Exploring an improved Ag based products that can control the release of Ag ions into the environment is crucial since there were some reports on the toxicity of silver nanoparticles on a common grass, Lollium multiflorum [10], freshwater alga Ochromonas danica [11] and aquatic custaceans (Daphnia magna and Thamnocephalus platyurus) [12]. The use of inorganic carrier to support antibacterial compounds could increase their antibacterial efficiency and could control the release of Ag ions.…”