Size of TiO2 nanoparticles influences their phototoxicity: an in vitro investigation
To uncover the size influence of TiO2 nanoparticles on their potential toxicity, the cytotoxicity of different-sized TiO2 nanoparticles with and without photoactivation was tested. It was demonstrated that without photoactivation, TiO2 nanoparticles were inert up to 100 μg/ml. On the contrary, with photoactivation, the toxicity of TiO2 nanoparticles significantly increased, which correlated well with the specific surface area of the particles. Our results also suggest that the generation of hydroxyl radicals and reactive oxygen species (ROS)-mediated damage to the surface-adsorbed biomolecules could be the two major reasons for the cytotoxicity of TiO2 nanoparticles after photoactivation. Higher ROS generation from smaller particles was detected under both biotic and abiotic conditions. Smaller particles could adsorb more proteins, which was confirmed by thermogravimetric analysis. To further investigate the influence of the generation of hydroxyl radicals and adsorption of protein, poly (ethylene-alt-maleic anhydride) (PEMA) and chitosan were used to coat TiO2 nanoparticles. The results confirmed that surface coating of TiO2 nanoparticles could reduce such toxicity after photoactivation, by hindering adsorption of biomolecules and generation of hydroxyl radical (·OH) during photoactivation.
KeywordsTitanium dioxide nanoparticles Phototoxicity Cytotoxicity Nanotoxicity Surface coating
The authors would like to acknowledge the financial support from the Agency for Science, Technology and Research (A*STAR) (Project No: 102 129 0098), the National Medical Research Council (NMRC/EDG/0062/2009) and the Nanyang Institute of Technology in Health & Medicine (NITHM), Singapore. Acknowledgements to the Ian Ferguson Postgraduate Fellowship for Sijing Xiong’s research attachment at the University of California, Los Angeles (UCLA). We thank Dr. Andre E. Nel and Dr. Tian Xian (UC Center for Environmental Implications of Nanotechnology) for their kind help in enabling this study.
Conflict of interest
The authors have declared no conflict of interest.
- Bar-Ilan O, Louis KM, Yang SP, Pedersen JA, Hamers RJ, Peterson RE, Heideman W (2011) Titanium dioxide nanoparticles produce phototoxicity in the developing zebrafish. Nanotoxicology, 1–10.doi: 10.3109/17435390.2011.604438
- George S, Pokhrel S, Xia T, Gilbert B, Ji Z, Schowalter M, Rosenauer A, Damoiseaux R, Bradley KA, Mädler L, Nel AE (2009) Use of a rapid cytotoxicity screening approach to engineer a safer zinc oxide nanoparticle through iron doping. ACS Nano 4(1):15–29. doi: 10.1021/nn901503q CrossRefGoogle Scholar
- George S, Xia T, Rallo R, Zhao Y, Ji Z, Lin S, Wang X, Zhang H, France B, Schoenfeld D, Damoiseaux R, Liu R, Lin S, Bradley KA, Cohen Y, Nel AE (2011b) Use of a high-throughput screening approach coupled with in vivo zebrafish embryo screening to develop hazard ranking for engineered nanomaterials. ACS Nano 5(3):1805–1817. doi: 10.1021/nn102734s PubMedCrossRefGoogle Scholar
- Horie M, Nishio K, Fujita K, Endoh S, Miyauchi A, Saito Y, Iwahashi H, Yamamoto K, Murayama H, Nakano H, Nanashima N, Niki E, Yoshida Y (2009) Protein adsorption of ultrafine metal oxide and its influence on cytotoxicity toward cultured cells. Chem Res Toxicol 22(3):543–553. doi: 10.1021/tx800289z PubMedCrossRefGoogle Scholar
- Vidosava BD (2004) Free radicals in cell biology. In: International review of cytology, vol 237. Academic Press, Serbia and Montenegro, pp 57–89Google Scholar
- Xia T, Kovochich M, Liong M, Mädler L, Gilbert B, Shi H, Yeh JI, Zink JI, Nel AE (2008) Comparison of the mechanism of toxicity of zinc oxide and cerium oxide nanoparticles based on dissolution and oxidative stress properties. ACS Nano 2(10):2121–2134. doi: 10.1021/nn800511k PubMedCrossRefGoogle Scholar
- Zhao X, Ng S, Heng BC, Guo J, Ma L, Tan TTY, Ng KW, Loo SCJ (2012) Cytotoxicity of hydroxyapatite nanoparticles is shape and cell dependent. Arch Toxicol, 1–16. doi: 10.1007/s00204-012-0827-1