Effects of the exposure of the clam Ruditapes philippinarum to gold nanoparticles. Evaluation of enzymatic and molecular endpoints

Abstract

Nanoparticles (NPs) are introduced into a growing number of commercial products, eventually leading to their release into the different environmental compartments (air, soil and surface waters). Up today, ecotoxicological risks i n non target organisms associated with NPs are poorly documented. Thus in this study, the marine bivalve Ruditapes philippinarum was chosen as ecotoxicological model to evaluate the enzymatic and molecular biomarkers of effects of exposure to gold nanopart icles (AuNPs). The organisms were exposed in the laboratory to gold added to natural filtered seawater either in the form of citrate reduced AuNPs (approximately 6 and 30 μg·L - 1 ) in the range of 20 – 30 nm or as soluble gold, H(AuCl 4 ) (50 μg·L - 1 ) for 28 da ys. Samples (digestive gland, gills and mantle) were taken throughout the exposure period in order to monitor the development of the expression of the chosen endpoints over time. Au concentrations and biomarkers of oxidative stress (catalase, GST, SOD, lip id peroxidation) were quantified in the three tissues. Metallothionein levels as a biomarker of metal exposure was evaluated both by HPLC and PCR approach. Additionally, different features involved in the inflammatory response, known to be induced by NPs i n other organisms, were monitored by quantitative real time PCR. Sections of gill and digestive gland tissue were observed under electron microscope (TEM/SEM) coupled to microanalysis (EDX). Our results show that exposure to AuNPs significantly alters the activity of the tested enzymes and also produces changes in the expression of metallothionein as well as of different, inflammation related features tested by PT - PCR.