Sublethal effects and bioaccumulation of "smart" anti-corrosion nanoadditives spiked in sediment in the ragworm...

Metallic corrosion poses an economic problem worldwide and is often mitigated by adding corrosion inhibitors (CIs) to protective coatings. Conventional CIs, such as 2-mercaptobenzothiazole (MBT) and benzotriazole (BTA), exhibit toxicity to aquatic biota, necessitating the development of eco-friendly alternatives. ZnAl layered double hydroxides (LDHs) have been used to immobilize CIs, reducing their toxicity and providing long-term protection through controlled release. This study evaluated the toxicity of CIs (MBT, BTA, bio-based sodium gluconate, and sodium nitrite, NaNO₂), their nanostructured forms (LDH-MBT, LDH-BTA, LDH-Gluconate, LDHNO₂), and the base nanomaterial (LDHNO₃). Adverse effects were assessed using the benthic polychaete Hediste diversicolor through a battery of biochemical biomarkers (AChE, LPO, CAT, and GST) and bioaccumulation analysis, coupled with the quantification of Al³⁺ and Zn²⁺ dissolution from the nanostructures in both aqueous and sedimentary compartments. Juveniles were individually exposed in spiked sediment at three concentrations (0.2, 2, 20 mg kg^-1) for 10 days. Metal concentration in water did not differ significantly from the control levels. Conversely, there was a significant decrease in Al³⁺ and Zn²⁺ in the sediment in most treatments compared to the control, with the exception of Zn²⁺ at the highest LDH-Gluconate and LDH-BTA exposure levels. Biochemical biomarkers indicated neurotoxicity induced by MBT, LDH-MBT, LDH-BTA, and LDHNO₃, with a decrease in AChE activity, despite no significant bioaccumulation. In contrast, the bio-based LDH-Gluconate and the bio-inspired LDHNO₂ exhibited no significant toxicity, representing promising eco-friendly options for marine anticorrosive applications.