Oxidative Stress as a Screening Metric of Potential Toxicity by Nanoparticles and Ariborne Particulate Matter

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Corrigendum

To the Editor:

In the January 20, 2008, issue, J. G. Ayres and colleagues put forth in a consensus document that oxidative stress should be viewed as a general metric to screen for the potential toxicity of airborne particles including engineered nanomaterials. This approach should be valid since biological oxidative stress has been shown in many studies to be a mediator of many acute and chronic diseases (Kelly, 2003). We agree that a screening technique to evaluate the degree of oxidative stress by particles is needed and that the approach should be simple, rapid, reliable, sensitive, robust, have low cost, high throughput, and produce results that are directly relevant to human health. However, the choice of sample type to use in the assay in the assessment of oxidative stress is also critical and must be carefully selected in order to correctly reflect the large scope of biological oxidative damage. This is important since oxidative stress if exerted by particulate matter in a biological system is complex and interactive and affected by the types of radicals introduced and/or formed as well the types and amounts of biochemical components and protective antioxidants in the biological milieu. These complexities suggest that only a real biological sample can give a realistic assessment of biological oxidative stress incurred. Cell-based techniques and even whole animals have been used but these are complicated, expensive, time-consuming, and hard to standardize and are not simple, which is requisite for a model screening approach. Simpler media have also been used to determine oxidative stress exerted by particles, such as aqueous solutions or pseudo-biological samples of lipids and proteins, but these may not reflect the full biological oxidative damage.

Human blood serum, used in vitro, may be a candidate physiological reaction medium. It contains an array of molecules that are subject to biological damage, such as proteins and unsaturated lipids, as well as a host of both water-soluble and lipid-soluble protective antioxidants. Using this type of physiological fluid, especially when combined with an assay that can monitor the decrease in total antioxidant capacity in the particle-exposed serum, may be an attractive approach to best assess the total extent of the biological stress elicited by the material being tested.