ARTICLE pubs.acs.org/ac Dextran Coated Ultrafine Superparamagnetic Iron Oxide Nanoparticles: Compatibility with Common Fluorometric and Colorimetric Dyes Sioned M. Griﬃths,† Neenu Singh,† Gareth J. S. Jenkins,† Paul M. Williams,‡ Alvin W. Orbaek, Andrew R. Barron,§ Chris J. Wright,‡ and Shareen H. Doak*,† § †Institute of Life Science, School of Medicine and ‡Multi-disciplinary Nanotechnology Centre, School of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP, Wales, U.K. §Department of Chemistry, The Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, Texas 77005, United States ABSTRACT: Due to the unique physicochemical properties of nanomaterials (NM) and their unknown reactivity, the possi- bility of NM altering the optical properties of ﬂuorometric/ colorimetric probes that are used to measure their cyto- and genotoxicity may lead to inaccurate readings. This could have potential implications given that NM, such as ultraﬁne super- paramagnetic iron oxide nanoparticles (USPION), are increas- ingly ﬁnding their use in nanomedicine and the absorbance/ ﬂuorescence based assays are used to assess their toxicity. This study looks at the potential of dextran-coated USPION (dUSPION) (maghemite and magnetite) to alter the background signal of common probes used for evaluating cytotoxicity (MTS, CyQUANT, Calcein, and EthD-1) and oxidative stress (DCFH-DA and APF). In the present study, both forms of dUSPION caused an increase in MTS signal but a decrease in background signal from calcein and 3'-(p-aminophenyl) ﬂuorescein (APF) and no eﬀect on CyQUANT and EthD-1 ﬂuorescence responses. Magnetite caused a decrease in ﬂuorescence signal of DCFH, but it did not decrease ﬂuorescence signal in the presence of the reactive oxygen species-inducer tert-butyl hydroperoxide (TBHP). In contrast, maghemite caused an increase in ﬂuorescence, which was substantially reduced in the presence of the antioxidant N-acetyl cysteine. This study emphasizes the importance of considering and controlling for possible interactions between NM and ﬂuorometric/ colorimetric dyes and, most importantly, the oxidation state of dUSPION that may confound their sensitivity and speciﬁcity. Tthe increased design and development of novel engineered he nanotechnology industry is growing at a rapid rate, with nanomaterials (NM), with diverse and wide ranging applications not only in industry, but also as consumer products and in the ﬁeld of medicine. The growing production and utilization of NM has inevitably resulted in increased occupational, clinical, and consumer exposure to these substances and is likely to lead to an accumulation of NM in the environment. However, as of yet the eﬀects these engineered substances have on human health and the environment especially, in the long term, still remain largely unknown. Over the last 5 6 years there has been a steady increase in studies focusing on the toxic eﬀects of NM,1 5 but this does not reﬂect the exponential growth in the nanotechnology industry. Thus, the ﬁrst report by the Royal Society and Royal Academy of Engineering Report in 2004, has been followed with several others including the European Scientiﬁc Committee on Emer- ging and Newly Identiﬁed Health Risks Report in 2006 and the DEFRA report in 2007, followed by another European Scientiﬁc Committee on Emerging and Newly Identiﬁed Health Risks Reports and a European commission joint research center institute for health and consumer protection report in 2009,6 10 all of which continue to emphasize the need for further study into the safety of NM. Traditional assays designed to quantify and characterize cellular damage, induced following exposure to exogenous agents, have been largely optimized for chemical compounds. However, given the unique physiochemical properties associated with NM, we cannot assume that they can be tested in the same way. For example, the possibility of direct interaction between NM and experimental assay components has the potential to result in false or misleading information, which could be a complicating factor in safety assessments. Some such instances have been documented in the literature, with reports demon- strating that single walled carbon nanotubes interact with a number of ﬂuorometric and colorimetric dyes, to give unex- pected results in cell viability assays.11 13 Furthermore, boron nitride nanotubes have been shown to interfere with the MTT cell viability test.14 It must also be stressed that due to the unique properties of each type of NM, we are currently unable to predict Received: February 1, 2011 Accepted: April 6, 2011 Published: April 06, 2011 r 2011 American Chemical Society 3778 dx.doi.org/10.1021/ac200103x | Anal. Chem. 2011, 83, 3778–3785