Singlet oxygen plays a key role in the toxicity and DNA damage caused by nanometric TiO2 in human keratinocytes

Abstract

Nanometric TiO2 has been reported to be cytotoxic and genotoxic in different in vitro models when activated by UV light. However, a clear picture of the species mediating the observed toxic effects is still missing. Here, a nanometric TiO2 powder has been modified at the surface to completely inhibit its photo-catalytic activity and to inhibit the generation of all reactive species except for singlet oxygen. The prepared powders have been tested for their ability to induce strand breaks in plasmid DNA and for their cytotoxicity and genotoxicity toward human keratinocyte (HaCaT) cells (100-500 μg mL(-1), 15 min UVA/B exposure at 216-36 mJ m(-2) respectively). The data reported herein indicate that the photo-toxicity of TiO2 is mainly triggered by particle-derived singlet oxygen. The data presented herein contribute to the knowledge of structure-activity relationships which are needed for the design of safe nanomaterials.

Surface reactivity and in vitro toxicity on human bronchial epithelial cells (BEAS-2B) of nanomaterials intermediates of the production of titania-based composites

“…2A). As expected an intense EPR spectra, corresponding to CO 2 •− radicals trapped by the spin trap DMPO was recorded for P25 suggesting a high amount of radical species generated (Fenoglio et al, 2013). Since the samples exhibit a high surface area, and are made of pure anatase, a high photo-reactivity was expected.…”

“…The ability of a particle to generate radical species was monitored by electron paramagnetic resonance (EPR) spectroscopy (Miniscope 100 EPR spectrometer, Magnettech, Berlin, Germany) using the spin trapping technique with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as trapping agent according to a procedure previously described (Fenoglio et al, 2013).…”

“…This reactivity is clearly related to its photo-toxicity (Dunford et al, 1997;Fenoglio et al, 2013) or ecotoxicity (Ma et al, 2011), while the role of such reactivity in the dark is still under debate (Sayes et al, 2006;Carlotti et al, 2009;Petkovic, 2011). Some of us previously proposed a series of protocols that may be used to assess the surface reactivity of TiO 2 (Corazzari et al, 2012;Fenoglio et al, 2013).…”

The influence of surface charge and photo-reactivity on skin-permeation enhancer property of nano-TiO2 in ex vivo pig skin model under indoor light

“…As a consequence of such ability to impregnate the first layers of SC as well as to form complexes with proteins and to induce the formation of free radicals (Borm et al, 2006;Turci et al, 2013;Carlotti et al, 2009Carlotti et al, , 2007Fenoglio et al, 2013Fenoglio et al, , 2011, nano-TiO2 could increase transdermal permeation of drugs or active ingredients, when used as an excipient in pharmaceutical products or as UV filter in sunscreen lotions.…”

Inhibition of the ROS-mediated cytotoxicity and genotoxicity of nano-TiO2 toward human keratinocyte cells by iron doping

“…The ability of TiO 2 nanoparticles to induce inhibition of cell viability as well as DNA damage under UV exposure is well documented (Xue et al 2010;Park et al 2011;Shukla et al 2011;Sanders et al 2012;Jaeger et al 2012;Fenoglio et al 2013). These effects are strictly related to the photogeneration of ROS by TiO 2 nanoparticles and, in particular, to the ability to generate singlet oxygen ).…”