Can non-invasive methods be used to assess effects of nanoparticles in fish?

The use of less invasive methods to assess the biological effects of xenobiotics on aquatic species is currently a research priority. Fish skin mucus appears as a promising biological matrix, allowing the assessment of biochemical endpoints with the advantage of non-invasive sampling. This study aimed to compare the sensitivity of plasma and skin mucus matrices in a marine fish, Sparus aurata, after 24 and 96 h exposure to 0.5 and 50 mu g.L-1 of 37 nm citrate coated gold nanoparticles (AuNP). Results showed a higher responsiveness of skin mucus, after 24 h exposure, in terms of total antioxidant capacity (TAC), as demonstrated by its increase for both concentrations when compared to the single increase, found in the 0.5 mu g.L-1 condition in blood plasma. The total oxidative status levels (TOS) did not appear as promising in skin mucus under the tested conditions, presenting levels below the detection limit whereas in blood plasma TOS levels were quantifiable and significantly increased after 96 h. Esterase activity (EA) was decreased in skin mucus after 24 h exposure to 0.5 mu g.L-1 AuNP, remaining unaltered in blood plasma. Cortisol, the main stress indicator in fishes, presented unaltered levels in both biological matrices and a positive correlation was found between cortisol and TAC. Overall, results support the use of skin mucus as a biological matrix and TAC and EA as potential biomarkers to monitor the effects of NP effects in fishes.