RESEARCH PAPER The effect of titanium dioxide nanoparticles on antioxidant gene expression in tilapia (Oreochromis niloticus) Ruth Varela-Valencia • Nikte Go ´mez-Ortiz • Gerko Oskam • Romeo de Coss • Jorge Rubio-Pin ˜a • Marcela del Rı ´o-Garcı ´a • Arnulfo Albores-Medina • Omar Zapata-Perez Received: 20 July 2013 / Accepted: 14 March 2014 / Published online: 1 April 2014 Ó Springer Science+Business Media Dordrecht 2014 Abstract The reactivity of nanoparticles (NPs) in biological systems is well recognized, but there are huge gaps in our understanding of NP toxicity in fish, despite a number of recent ecotoxicity studies. There- fore, the aim of this research was to evaluate the effect of titanium dioxide NPs (TiO 2 -NPs) on antioxidant gene expression in the tilapia, Oreochromis niloticus. First, different sizes, shapes, and phases of TiO 2 -NPs were synthesized and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and dynamic light scattering (DLS). Fish were injected intraperitoneally with different concen- trations (0.1, 1.0, 10.0 mg/L), sizes (7, 14, and 21 nm), and phases (anatase and rutile) of TiO 2 -NPs, and sacrificed 3, 6, 12, and 24 h after injection, when their livers were removed. Total RNA was extracted, and expression of the catalase (CAT), glutathione-S-trans- ferase (GST), and superoxide dismutase (SOD) genes was assessed by real-time polymerase chain reaction (RT-PCR). The results showed that injection of 1.0 mg/L TiO 2 -NPs induced an initial mild increase in CAT, GST, and SOD gene expression in tilapia, after which transcript levels decreased. Fish injected with 7 and 14 nm TiO 2 -NPs showed an increase in antiox- idant transcript levels 6 h after treatment. Finally, the rutile form generated stronger induction of the GST gene than anatase TiO 2 -NPs during the first 6 h after injection, which suggests that exposure to rutile causes higher levels of reactive oxygen species to be produced. Keywords Nanomaterials  Titanium dioxide  Oxidative stress  Gene expression  Nanobiotechnology Introduction From an ecotoxicological perspective, titanium diox- ide nanoparticles (TiO 2 -NPs) are by far the most extensively studied metal oxide nanoparticles (NPs) (Kahru and Dubourguier 2010). TiO 2 has many uses, for example, in medical science (Emerich and Thanos 2003), drug delivery, the agriculture and defense industries (Long et al. 2007), and environmental R. Varela-Valencia (&)  J. Rubio-Pin ˜a  M. del Rı ´o-Garcı ´a  O. Zapata-Perez Departamento de Recursos del Mar, Centro de Investigacio ´n y de Estudios Avanzados del Instituto Polite ´cnico Nacional, Cinvestav-Me ´rida, Km 6 Antı ´gua Carretera a Progreso., C.P. 97310 Me ´rida, Yucata ´n, Mexico e-mail: vruth77@gmail.com; rvarela@mda.cinvestav.mx N. Go ´mez-Ortiz  G. Oskam  R. de Coss Departamento de Fı ´sica Aplicada, Centro de Investigacio ´n y de Estudios Avanzados del Instituto Polite ´cnico Nacional, Me ´rida, Yucata ´n, Mexico A. Albores-Medina Departamento de Toxicologı ´a, Centro de Investigacio ´n y de Estudios Avanzados del Instituto Polite ´cnico Nacional, Me ´xico D.F, Mexico 123 J Nanopart Res (2014) 16:2369 DOI 10.1007/s11051-014-2369-3