Effect of Titanium dioxide nanoparticles in Enzymatic Activity of Epigeic Earthworm species “Eudrilus eugenia”

Abstract

Titanium dioxide nanoparticles (TiO2 NPs) are commonly used in different industries because of their physico-chemical properties. They are widely used and their environmental occurrence has raised concerns about the potential toxicity as the release of nanoparticles to the soil directly or indirectly through air and water is gradually increasing. The soil is contaminated with nanoparticles in the long term and soil microorganisms can adversely be affected by these accumulated nanoparticles. Studies show that nanoparticles can have a lethal effect on soil microorganisms by causing the production of reactive oxygen species, by damaging the membrane permeability, cell signaling processes and the stability of enzymes and protein structures. In this study, Eudrilus eugenia earthworms were exposed to varying concentrations of TiO2 nanoparticles for a specified duration. Enzymatic activity assays were performed to evaluate the impact of nanoparticle exposure on key enzymes involved in antioxidant defense systems such as glutathione peroxidase (GPx) superoxide dismutase (SOD), glutathione reductase (GR) detoxification enzymes and glutathione S-transferases (GSTs). The activity of acetylcholinesterase (AChE), an enzyme involved in neurotransmission, was also assessed. The results demonstrated the exposure to TiO2 nanoparticles significantly altered the enzymatic activity of Eudrilus eugenia earthworms. The activity of GPx and GR enzymes exhibited a concentration-dependent decrease (0, 5, 50 and 500 mg/kg), indicating a disruption in antioxidant defense mechanisms. This disruption suggests a potential imbalance between reactive oxygen species (ROS) and antioxidant capacity, leading to oxidative stress. The superoxide dismutase (SOD) activity and the reduced glutathione/oxidized glutathione (GSH/GSSG) ratio significantly decreased under the 500 mg/kg nTiO2 treatment. Also, the activity of AChE was found to be significantly affected by TiO2 nanoparticle exposure, suggesting potential disruption in neurotransmission processes.