Toxicological Aspects of the Effects of Titanium Dioxide Nanoparticles (nano-TiO2) on Marine Invertebrates

Abstract

In recent years, the marine environment has received an enormous amount of different pollutants in unprecedented quantities in the history of mankind. Among these, nanoparticles (NPs) are a source of emerging, diffuse and difficult to remediation environmental pollution, becoming a large and growing environmental problem. Between the different types of NPs, titanium dioxide (nano-TiO2) is the most used, present in numerous products for human consumption. Because of this wide use, nano-TiO2 can be easily inserted into marine ecosystems, causing immeasurable damages. In this way, the use of different tools that evaluate and express the extent of the damages of these emerging contaminants is becoming increasingly necessary for the future environmental scenario, since it is estimated that in 2025 the production of nano-TiO2 will reach 2,5 million tons per year. Among marine invertebrates, sea urchins and bivalve molluscs are considered excellent environmental bioindicators, even in embryonic stages, in the case of sea urchins. These are capable of accumulating, interacting and reflecting the stimuli from local environmental pressure. In bivalves, exposure to NPs can cause different damages, making them more vulnerable and favoring the appearance of parasites, leading not only to environmental impacts but also economic and public health ones, due to exposure through human consumption. In sea urchins, exposure to nano-TiO2 during early stages of life may implicate with the development and establishment of these animals, especially in coastal waters, where NPs are less diffuse and in higher concentrations, leading to environmental impacts. Considering the harmful effects of nano-TiO2 in the Mediterranean marine environment, this project aims to evaluate the effects of exposure to nano-TiO2 on embryos of sea urchin Lytechinus variegatus and on the innate immune system of white shellfish Mesodesma mactroides. Therefore, different methodologies will be used to evaluate the nano-TiO2 data in different organisms. In embryos of sea urchins will be evaluated morphological parameters, like anatomical malformations and delay in different stages of development (gastrula and pluteus), besides evaluating the effects during fertilization; transcriptional profile of genes and components of signaling pathways induced against environmental stress (HSPs and MPKs); and the possible accumulation by transmission electron microscopy. Different parameters of the innate immune response will be evaluated in bivalve molluscs through the phagocytic activity of their hemocytes, germicidal capacity, differential count, total and evaluation of cellular functions after acute exposures, besides the protein expression of HSP70. The results of this project will bring new perspectives to the potential impact of nano-TiO2 both during the development of sea urchin and in the innate immune system of bivalves, contributing with new tools for biomonitoring in the marine environment tropical. (AU)