Nano-Ecotoxicology of Natural and Engineered Nanomaterials for Microorganisms

Abstract

The mobility of nanomaterials (NMs) varies according to their surface charges, polarity and the media properties they come into contact. When compared to bulk materials their degradability is lower and solubility is slower. These two facts result in longer bioavailability periods and increased possibility of transport to further distances. In general terms, all of NMs produce toxic effects in living organisms, again depending on the interaction with the surrounding media. Given the possibility of enhanced transport, it could be assumed that soon or later NMs will reach environmental conditions that trigger their toxic effects to the local biota. The physiological pathway they trigger is linked to the cellular production of Reactive Oxygen Species (ROS), which would further result in reduction of cellular growth and even cell death, depending on the concentrations of NMs and the sensibility of the given organism. NMs’ toxicity and transport can vary with 1) time (due to changes suffered once in the environment), 2) space (due to seasonal or other fluctuations in environmental features), and 3) the species. Therefore, a general protocol for NMs testing should be developed. In general, such a general protocol should use NMs and their aged derivates for determination of toxicity in at least three local species of different trophic levels under different conditions (e.g., temperature, light, or environmental conditions such as different dissolved organic matters, aerobic or anaerobic settings) (Blaise et al. 2008). There are a large number of standardized bioassays that can be also used for evaluating NMs toxicity. All of them use different medium conditions and different target organisms, which can produce significantly different results.This chapter focuses on nano-ecotoxicology of natural and engineering NMs for microorganisms. The chapter starts with mobility, bioavailability and degradability of NMs in the environment, and then moves into general considerations of toxicity and eco-toxicity of NMs, followed by discussions about the comet and the micronucleus assays, including the K micronuclei and Ames tests and Highthroughput screening and current status in the related areas.