Review Article Measurement of Oxidative Damage to DNA in Nanomaterial Exposed Cells and Animals Peter Mïller, 1 * Ditte Marie Jensen, 1 Daniel Vest Christophersen, 1 Ali Kermanizadeh, 1 Nicklas Raun Jacobsen, 2 Jette Gjerke Hemmingsen, 1 Pernille Hïgh Danielsen, 1 Dorina Gabriela Karottki, 1 Martin Roursgaard, 1 Yi Cao, 1 Kim Jantzen, 1 Henrik Klingberg, 1 Lars-Georg Hersoug, 1 and Steffen Loft 1 1 Department of Public Health, Section of Environmental Health, University of Copenhagen, Copenhagen K, Denmark 2 The National Research Centre for the Working Environment, Copenhagen, Denmark Increased levels of oxidatively damaged DNA have been documented in studies of metal, metal oxide, carbon-based and ceramic engi- neered nanomaterials (ENMs). In particular, 8- oxo-7,8-dihydroguanine-2’-deoxyguanosine (8- oxodG) is widely assessed as a DNA nucleo- base oxidation product, measured by chromato- graphic assays, antibody-based methods or the comet assay with DNA repair enzymes. How- ever, spurious oxidation of DNA has been a problem in certain studies applying chromato- graphic assays, yielding high baseline levels of 8-oxodG. Antibody-based assays detect high 8- oxodG baseline levels, related to cross-reactivity with other molecules in cells. This review pro- vides an overview of efforts to reliably detect oxidatively damaged DNA and a critical assess- ment of the published studies on DNA damage levels. Animal studies with high baseline levels of oxidatively damaged DNA are more likely to show positive associations between airway exposure to ENMs and oxidized DNA in lung tissue than studies showing acceptable baseline levels (odds ratio 5 12.1, 95% confidence inter- val: 1.2–124). Nevertheless, reliable studies indicate that intratracheal instillation of nano- sized carbon black is associated with increased levels of oxidatively damaged DNA in lung tis- sue. Oral exposure to nanosized carbon black, TiO 2 , carbon nanotubes and ZnO is associated with elevated levels of oxidatively damaged DNA in tissues. These observations are sup- ported by cell culture studies showing concentration-dependent associations between ENM exposure and oxidatively damaged DNA measured by the comet assay. Cell culture stud- ies show relatively high variation in the ability of ENMs to oxidatively damage DNA; hence, it is currently impossible to group ENMs accord- ing to their DNA damaging potential. Environ. Mol. Mutagen. 00:000–000, 2014. V C 2014 Wiley Periodicals, Inc. Key words: diesel exhaust particles; FPG; hOGG1; methylmethane sulfonate; Printex 90; 8-oxodG INTRODUCTION Assays for the detection of oxidatively damaged DNA in cells and animal tissues have been incorporated into the “standard” battery of nanotoxicology testing methods [Johnston et al., 2013]. Nevertheless, a number of publi- cations on measurement of oxidatively damaged DNA suggest that some researchers in the field of nanotoxicol- ogy may not be familiar with the extensive effort that has been deployed in the validation of assays for oxidatively damaged DNA. The present review provides an overview of the efforts to detect oxidatively damaged DNA, with a Additional Supporting Information may be found in the online version of this article. Grant sponsors: Center for Pharmaceutical Nanotechnology and Nanotoxi- cology, the Lundbeck Foundation “Center for Biomembranes in Nano- medicine” and “Danish Centre for Nanosafety” from the Danish Working Environment Research Foundation; Grant number: 20110092173/3. *Correspondence to: Peter Mïller, Department of Public Health, Section of Environmental Health, University of Copenhagen, Øster Farimags- gade 5A, Building 5B, 2nd Floor, DK-1014 Copenhagen, Denmark. E-mail: pemo@sund.ku.dk Received 10 June 2014; provisionally accepted 20 August 2014; and in final form 21 August 2014 DOI 10.1002/em.21899 Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com). V C 2014 Wiley Periodicals, Inc. Environmental and Molecular Mutagenesis 00:00^00 (2014)