Assessment of deep eutectic solvents toxicity in zebrafish (Danio rerio)

Deep Eutectic Systems (DES) have emerged as a "green alternative" to organic solvents and have been coined as biocompatible and biodegradable. However, the number of studies concerning the real biodegradability and biocompatibility are scarce. Thus, to study the toxicity of certain DES, two different approaches were used: i) zebrafish exposure via water, where the system (DES) was tested at potentially realistic environmental concentrations and ii) via intraperitoneal injection, where the system was tested in different concentrations, relevant to the pharmaceutical industry. These studies were performed using zebrafish, a standardized animal model often used in biomedicine and toxicological assays. The results show low toxicity according to tested concentrations (up to 73.47 μM), when the system CA:T:W, with a 2:1:3 molar ratio, was tested through exposure via water and also in the intraperitoneal injection tests with concentrations up to 6000 μM. The activity of different enzymes involved in antioxidant pathways (glutathione S-transferase, catalase, glutathione peroxidase), the total antioxidant capacity (TAC) and lipoperoxidation (MDA content) were determined suggesting low toxicity of the tested system (DES). The promising results herein presented show that DES present the potential to be used as the new class of green solvents, not only for use in the pharmaceutical industry, but also in cosmetic and chemical engineering processes without causing negative impact on living organisms.