Understanding the Genotoxic Potential of Ultra-Fine Superparamagnetic Iron Oxide Nanoparticles

The nanotechnology industry is promising to develop new nanometer-sized materials (a millionth of a millimetre) that can significantly enhance our quality of life. However, the impact of these products upon human health and the environment is currently unknown. An important area governing health risk assessment is genotoxicology, which involves the study of genetic damage following exposure to new compounds. Such information is vital as DNA damage can cause cancer and can have an impact upon fertility and health of subsequent generations. Consequently, it is imperative that a clear understanding of the impact of nanomaterials on biological function is established. In the proposed study, we will examine the cellular and genetic damage induced by ultra-fine superparamagnetic iron oxide nanoparticles (USPION), which are destined for numerous purposes in medical diagnostics and treatments. We therefore aim to answer two main questions: 1. Do these nanoparticles cause genetic damage; 2. If so, at what concentrations does this genotoxicity arise. To achieve this, we will quantify the level of damage that occurs over a broad USPION concentration range in cultured human cells. Our experiments will therefore provide important information that could lead to the determination of safe exposure levels, facilitating health risk assessment. A secondary impact of this study is a reduced requirement for toxicity testing in animals, as it will identify the specific USPION concentrations that may need further assessment. Furthermore, it is also possible that if the USPION induce no cellular damage in the cultured cells, or if they only induce damage at excessively higher concentrations than expected occupational or medical exposures, then there will be little need for further testing in animals.

The industrial production of nanomaterials is rapidly increasing, with a number already finding their way into consumer products. However, this has prompted safety concerns with a clear need to identify health and environmental safety issues. An important area governing health risk assessment is genotoxicology, as DNA damage not only indicates potential carcinogenicity, but can also have an impact upon fertility and health of subsequent generations if disturbances arise in germ cells. Consequently, there is an urgent requirement for thorough studies generating quantitative genotoxicology data for nanomaterials and investigations into their mechanisms of action.
The aim of the current proposal is to establish the genotoxic potential of ultra-fine superparamagnetic iron oxide nanoparticles (USPION), both uncoated and when coated with compounds that increase the cellular internalisation and hence biocompatibility of the nanoparticles. In vitro pre-screening tests with a range of cellular endpoints will be utilised. We will characterise the physical features of the USPION under examination and perform comprehensive dose-response assays to determine the relationship between exposure levels and DNA damage. The micronucelus assay will be utilised to quantify the induction of chromosomal damage and to determine whether or not the nanoparticles are clastogenic or aneugenic, while the induction of point mutations will be assessed with the HPRT forward mutation assay. Additionally, quantitative assays for cell proliferation and cytotoxicity (distinguishing between apoptosis and necrosis) will be performed, as will studies to establish whether or not USPION exposure results in oxidative stress.
The quantitative dose-response data generated during the course of this study will therefore yield essential information necessary for health risk assessments, and will also provide the basis for defining the level of further analysis needed, resulting in a reduced requirement for universal genotoxicity testing in vivo. The ability of the USPION to induce oxidative stress may provide insights into the mechanisms of genotoxicity imparted by ultra-fine nanoparticles and we will determine if two of the most frequently used coatings (dextran and polyethylene glycol), alter the genotoxic potential of the UPSION. In the future this data will be central to developing predictive in silico toxicity models according to the physio-chemical characteristics of the materials under investigation, which would potentially allow extrapolation of the toxicity information to other compounds with similar properties.