The past decade has seen the emergence of a new class of manufactured materials known as engineered nanomaterials (ENMs); generally defined as materials having at least one dimension at the nanoscale (1-100 nm). They are produced in vast amounts all over the world and designed with different properties e.g. sizes, shapes, and compositions, to be used in consumer products and for different industrial or medical applications. Increasing global production volumes of ENMs inevitably result in their release into aquatic ecosystems. This raised some safety issues regarding the possible toxicity of these materials for biota and for humans. The first decade of research leads to the conclusion that the expected levels of environmental release of ENMs are not likely to cause acute toxicity. Some metal-based (MB)-ENMs, e.g. gold(Au) ENMs, and carbon-based ENMs, e.g. carbon nanotubes (CNTs), are persistent materials in the environment and in biota. Other MB-ENMs in water will, subsequently, fully or partly dissolve to their constituent ions. Recently it has been reported that dissolvable MB-ENMs do not require nano-specific hazard assessment, and instead, read-across of the properties of the dissolved materials to the corresponding bulk materials may be used. On the other hand, concern has been raised about bioaccumulation and biomagnification of CNTs and persistent MB-ENMs in organisms and subsequent chronic toxicity. Consequently, novel research questions pop up, such as: Do CNTs and persistent MB-ENMs bioaccumulate in organisms? Are they transferred through food chains and induce biomagnification in predators to subsequently cause chronic effects? Which physicochemical properties of ENMs modify these processes? There are currently gaps of knowledge in understanding the underlying processes and lack of concepts to model these processes for ENM risk assessment. Herein, my ambition is to provide novel approaches to some of the major knowledge gaps
that the nanosafety community will need to address for ENM-tailored risk assessment.
Objective 1: Systematic quantification of bioaccumulation and biodistribution of SWCNTs (as a function of size) and Au ENMs (as a function of size, shape and surface coating) in D. magna and D. rerio at chronic exposure conditions. I will demonstrate whether ENMs that are composed of the same core but differ with regard to the mentioned properties, also differ with regard to their bioaccumulation and biodistribution.
Objective 2: Study the influence of particle size, shape and surface coating of Au ENMs and size of SWCNTs on their trophic transfer along an assembled aquatic food chain consisting of a primary producer (C. pyrenoidosa) and a primary (D. magna) and a secondary consumer (D. rerio). I will demonstrate whether SWCNTs and Au ENMs can be transferred to higher trophic levels, how the properties of the particles influence the bioavailability of SWCNTs and Au ENMs in D. magna to D. rerio and how the properties of the particles influence the biodistribution of the ENMs in D. rerio.
Objective 3: Study the potential for biomagnification of SWCNTs and Au ENMs in an assembled aquatic food chain when mass and particle number concentration are considered as dose metrics. The algae and Daphnia will be exposed to a mixture of three different sizes of SWCNTs or a mixture of three different sizes of Au ENMs. I will (a) demonstrate whether particles number concentration is a suitable dose metric to investigate the biomagnification of ENMs and (b) develop a model for predicting biomagnification of ENMs based on the proper dose metric.
