Ecotoxicological evaluation of commercial nanosilver-based products vs bifunctionalized silver nanoparticles: towards new environmentally safe nanosilver-based products

ARIANNA BELLINGERI, ; IMENA CAZENAVE ; IOLE VENDITTI, ; ILARIA CORSI; ANALÍA ALE, ; CHIARA BATTOCCHIO, J

Florianopolis

Simposio; II Karyokinesis Symposium; 2020

Silver nanoparticles (AgNP) are one of the most produced and used nanoproducts in the entire world due to their unique properties, especially as a biocide. AgNP have been widely applied against bacterial and fungal proliferation and they were proved to have a synergistic effect when mixed with antibiotics. Moreover, in recent years other applications were developed thanks to their highly tunable properties, for instance, AgNP as plasmonic nanosensors for the selective detection of heavy metals in water. However, as the number of nanoparticle applications increases, also are the chances of uncontrolled release and discharge into the aquatic environment, with the consequent interaction with inorganic and organic compounds and biota leading to possible deleterious effects. Therefore, ecotoxicological assessments must be carried out to understand, and in a best-case scenario prevent, the vulnerability of the ecosystems. This study aimed to evaluate and compare the ecotoxicity of novel AgNP bifunctionalized with citrate and L-cysteine (AgNP Cit/L-cys) (5 nm-sized) with a commercial formulation containing AgNP functionalized with polyvinylpyrrolidone (PVP) (AgNP PVP) (nanArgen®) (20-40 nm-sized). Laboratory assays were carried out employing two test species: the microalgae Phaeodactylum tricornutum and the crustacean Artemia franciscana. The microalgae were exposed to 0, 1, 5, 100, 500, and 1000 µg L-1 of AgNP Cit/L-cys or AgNP PVP (with six replicates per treatment), and after 72 h, the growth inhibition was analyzed. The assays were carried out with standard medium (F/2 prepared with natural seawater -NSW-) at controlled temperature (21 ± 1 °C) and in constant light. A. franciscana was exposed to 0, 0.1, 1, 10, and 100 mg L-1 to AgNP Cit/L-cys or AgNP PVP (with three replicates per treatment), and the mortality was evaluated after 24 and 48 h. The assays were performed using stock dispersed in NSW, at controlled temperature (25 ± 1 °C), and in dark conditions. The results showed no significant toxic effects to both test species in case of exposure to AgNP bifunctionalized formulation while, on the other hand, the commercial product containing AgNP PVP caused a dose-dependent growth rate inhibition in P. tricornutum starting from 100 µg L-1. In the case of A. franciscana, mortality was observed already after 24 h at 100 and 1000 mg L-1 of AgNP PVP formulation, which was exacerbated after 48 h at the highest concentration. The obtained data suggested the ecosafety of AgNP Cit/L-cys, in comparison with the commercial nanoproduct (AgNP PVP), probably due to the coating composition. AgNP Cit/L-cys coating design, in fact, probably played a key role in reducing the release of Ag ions, which represents one of the most important toxicity mechanisms of AgNP in aquatic biota. Currently, the use of AgNP is not strictly regulated by the authorities even if their frequency of use and application in commercial products is increasing. This situation has generated an increasing load of AgNP with unknown toxicological implication to enter the aquatic systems since no attention was given to their chemical design. The importance of this study lies in the need for development of more ecofriendly nanomaterials. Overall, we highlight the importance of nanoparticle design and encourage further studies to evaluate ecofriendly alternatives to take advantage of the increasing nanotechnological developments.