Ecotoxicological effects of silver nanoparticles in marine mussels

Abstract

In the marine bioindicator species M. galloprovincialis Lam we predicted toxicity and bioaccumulation of 5 nm alkane-coated and 50 nm uncoated silver nanoparticles (AgNPs) along with Ag+, as a function of the actual dose level. We generated a time persistence model of silver concentration in seawater and used the Area Under the Curve (AUC) as independent variable in hazard assessment. This approach allowed us to evaluate unbiased ecotoxicological endpoints for acute (survival) and chronic toxicity (byssal adhesion). Logistic regression analysis rendered LC5096h values of 0.68 ± 0.08; 1.00 ± 0.20; 1.00 ± 0.42 mg h L-1 respectively for Ag+, 5 nm and 50 nm AgNP posing no evidence the silver form is a necessary variable to predict the survival outcome. By contrast, for byssal adhesion regression analysis revealed a much higher toxicological potential of Ag+ vs AgNPs, 0.0021 ± 0.0009; 0.053 ± 0.016; 0.021 (no computable error for 50 nm AgNP) mg h L-1, and undoubtedly confirmed a role of the silver form. Bioaccumulation was higher for Ag+ > 5 nm AgNP > 50 nm AgNP reflecting a parallel with the preferential uptake route / target organ. We, eventually, provided a full range of toxicological endpoints to derive risk quotients.

In-Gel Assay to Evaluate Antioxidant Enzyme Response to Silver Nitrate and Silver Nanoparticles in Marine Bivalve Tissues

“…The concentration range of silver used in the current work (0.2-20 µgL −1 ) is from a previous work in which we evaluated the ecotoxicological range of silver nitrate and silver nanoparticles for acute and chronic effects. All concentrations are completely sublethal, but in the case of silver nitrate, the highest two concentrations (20 and 2 µgL −1 ) are within the range of an effective concentration for the inhibition of byssus synthesis (below EC50) [39]. Our data (this work) show that silver nitrate is capable of eliciting biochemical effects even at lower doses (e.g., 0.2 µgL −1 ), as noted for CAT and SOD activities in both gills and digestive glands.…”

“…On the other hand, particulate silver, i.e., nanoparticles, are also found in the digestive gland, probably following the feeding pathway after having undergone an increase in size in seawater due to the loss of zeta-potential. Our best explanation for this difference between the two metal forms-in terms of biochemical effects-is based on the higher reactivity and bioavailability of silver nitrate compared to silver nanoparticles, which, as mentioned, tend to be more unstable in seawater [39]. Indeed, silver nanoparticles tend to form aggregates when the surface potential suddenly changes due to pH and ionic strength [48].…”

“…In addition, it should be considered that a long exposure time (28 days) may have allowed a compensatory response of the antioxidant enzyme system, which could have occurred earlier with nanoparticle exposure essentially because of the overall lower dose, due to the aggregation and precipitation of nanoparticles [39]. Previously published data on the effects of 3-15-day exposure of silver NP in marine mollusks showed that CAT, SOD, and GPX activity in the gills increased linearly with time [27], but in another study using similar concentrations of a silver NP for 94 h, no effects were reported for CAT and very little change for GST, another common antioxidant system [9].…”

“…AgNPs were added daily to the experimental samples from a stable suspension of 1 g L −1 prepared by the manufacturer (Amepox ® , Lodz, Poland) in ultrapure water. These particles have been described elsewhere [38,39]. Silver nitrate from a stock solution of 1 g Ag+ L −1 prepared in acidified ultrapure water was also used.…”

Polystyrene nanoplastics mediated the toxicity of silver nanoparticles in zebrafish embryos

“…The structural morphology of PS nanoplastics, AgNPs, and their mixture in exposure solution was characterized by High-Resolution Transmission Electron Microscopy (TEM) (JEM-2100F, JEOL, Japan). The zeta potentials and z-average hydrodynamic diameters of the AgNPs alone and in combination with PS microplastics in the suspension solution during the exposure periods were also examined using a Zetasizer Nano ZS90 (Malvern, UK), as described by Calisi et al (2022).…”