Cytotoxicity of commercial nano-TiO2 to Escherichia coli assessed by high-throughput screening: effects of environmental factors.

The extensive use of nano-TiO2 in industry has led to growing concerns about its potential environmental impacts. However, negligible toxicity is commonly reported under insufficient illumination and artificial solution conditions in the literature, which rarely includes discussion of the regulating role of environmental factors. Herein, we report the results of a high-throughput screening assay to evaluate the acute cytotoxicity of six commercial nano-TiO2 materials to Escherichia coli (E. coli) using Lake Michigan water as a model for aquatic surface environments. In particular, we investigate the specific effects of illumination wavelength and natural organic matter (NOM) content. Under simulated solar irradiation, four anatase-based nano-TiO2 materials including Pigment White 6 exhibit significant bacterial toxicity (2 h-IC50 value of 2.7-9.1 mg/L), with toxicity thresholds much lower than previously reported. Negligible toxicity is caused either by pure-phase rutile or under dark condition. Formation of nano-TiO2 aggregates well beyond nano-scale does not eliminate their toxic effect, but photoactivity dominates over the primary size and extent of aggregation in determining the acute cytotoxicity of nano-TiO2. Under visible light irradiation (UVA&B blocked) the antibacterial activity of nano-TiO2 is essentially erased, whereas removing only UVB wavelengths slightly mitigates the toxicity. Suwannee River fulvic acid, acting as a natural dispersant, reverses the extent of nano-TiO2 aggregation, but also reduces its bacterial cytotoxicity. These results demonstrate that despite particle aggregation, the short-term cytotoxicity of nano-TiO2 is predominantly attributed to its phototoxicity, emphasizing the importance of illumination conditions in toxicological screening of photoactive nanomaterials. In the natural aquatic environment, however, this acute toxicity may be mitigated by the attenuation of UV irradiation and increased NOM concentration in the water column.

[1]  P. Westerhoff,et al.  Titanium dioxide nanoparticles in food and personal care products. , 2012, Environmental science & technology.

[2]  Pedro J J Alvarez,et al.  Comparative eco-toxicity of nanoscale TiO2, SiO2, and ZnO water suspensions. , 2006, Water research.

[3]  Kerstin Hund-Rinke,et al.  Ecotoxic Effect of Photocatalytic Active Nanoparticles (TiO2) on Algae and Daphnids (8 pp) , 2006, Environmental science and pollution research international.

[4]  Hongtao Wang,et al.  Stability and aggregation of metal oxide nanoparticles in natural aqueous matrices. , 2010, Environmental science & technology.

[5]  Anne Kahru,et al.  Toxicity of nanosized and bulk ZnO, CuO and TiO2 to bacteria Vibrio fischeri and crustaceans Daphnia magna and Thamnocephalus platyurus. , 2008, Chemosphere.

[6]  Arturo A. Keller,et al.  TiO2 Nanoparticles Are Phototoxic to Marine Phytoplankton , 2012, PloS one.

[7]  J. West,et al.  Correlating nanoscale titania structure with toxicity: a cytotoxicity and inflammatory response study with human dermal fibroblasts and human lung epithelial cells. , 2006, Toxicological sciences : an official journal of the Society of Toxicology.

[8]  Zhenyao Shen,et al.  Toxicological assessment of TiO2 nanoparticles by recombinant Escherichia coli bacteria. , 2011, Journal of environmental monitoring : JEM.

[9]  Pedro J. J. Alvarez,et al.  Nanomaterials in the construction industry: a review of their applications and environmental health and safety considerations. , 2010, ACS nano.

[10]  Craig E. Williamson,et al.  The attenuation of solar UV radiation in lakes and the role of dissolved organic carbon , 1995 .

[11]  J. Herrmann,et al.  Photocatalytic degradation pathway of methylene blue in water , 2001 .

[12]  B. Ohtani,et al.  Is methylene blue an appropriate substrate for a photocatalytic activity test? A study with visible-light responsive titania , 2006 .

[13]  G. Lowry,et al.  Towards a definition of inorganic nanoparticles from an environmental, health and safety perspective. , 2009, Nature nanotechnology.

[14]  F. Hong,et al.  Biochemical Toxicity of Nano-anatase TiO2 Particles in Mice , 2008, Biological Trace Element Research.

[15]  Awadhesh N Jha,et al.  Hydroxyl radicals (*OH) are associated with titanium dioxide (TiO(2)) nanoparticle-induced cytotoxicity and oxidative DNA damage in fish cells. , 2008, Mutation research.

[16]  Andrew P Worth,et al.  A theoretical framework for predicting the oxidative stress potential of oxide nanoparticles , 2011, Nanotoxicology.

[17]  T. Xia,et al.  Toxic Potential of Materials at the Nanolevel , 2006, Science.

[18]  F. Collins,et al.  Transforming Environmental Health Protection , 2008, Science.

[19]  Andrew P. Worth,et al.  QSAR modeling of nanomaterials. , 2011, Wiley interdisciplinary reviews. Nanomedicine and nanobiotechnology.

[20]  Richard M. Lueptow,et al.  Controlling biofilm growth using reactive ceramic ultrafiltration membranes , 2009 .

[21]  Mark R Wiesner,et al.  Comparative photoactivity and antibacterial properties of C60 fullerenes and titanium dioxide nanoparticles. , 2009, Environmental science & technology.

[22]  David Jassby,et al.  Impact of aggregate size and structure on the photocatalytic properties of TiO2 and ZnO nanoparticles. , 2012, Environmental science & technology.

[23]  Saji George,et al.  Role of Fe doping in tuning the band gap of TiO2 for the photo-oxidation-induced cytotoxicity paradigm. , 2011, Journal of the American Chemical Society.

[24]  W. Macyk,et al.  Singlet oxygen photogeneration at surface modified titanium dioxide. , 2006, Journal of the American Chemical Society.

[25]  Jian Li,et al.  Improved photocatalytic activity of polymer-modified TiO2 films obtained by a wet chemical route , 2012, Journal of Materials Science.

[26]  Yu Wang,et al.  Dispersion and toxicity of selected manufactured nanomaterials in natural river water samples: effects of water chemical composition. , 2009, Environmental science & technology.

[27]  Xiaobo Chen,et al.  Titanium dioxide nanomaterials: synthesis, properties, modifications, and applications. , 2007, Chemical reviews.

[28]  M. Elrod-Erickson,et al.  Effects of silver nanoparticles on zebrafish (Danio rerio) and Escherichia coli (ATCC 25922): A comparison of toxicity based on total surface area versus mass concentration of particles in a model eukaryotic and prokaryotic system , 2012, Environmental toxicology and chemistry.

[29]  P. Huovinen,et al.  Spectral attenuation of solar ultraviolet radiation in humic lakes in Central Finland. , 2003, Chemosphere.

[30]  J. Hughes,et al.  Escherichia coli Inactivation by UVC-Irradiated C60: kinetics and mechanisms. , 2011, Environmental science & technology.

[31]  K. Gray,et al.  The solid–solid interface: Explaining the high and unique photocatalytic reactivity of TiO2-based nanocomposite materials , 2007 .

[32]  Jamie R Lead,et al.  Silver nanoparticle impact on bacterial growth: effect of pH, concentration, and organic matter. , 2009, Environmental science & technology.

[33]  M A Kiser,et al.  Titanium nanomaterial removal and release from wastewater treatment plants. , 2009, Environmental science & technology.

[34]  Z. Zainal,et al.  Bactericidal Activity of TiO2 Photocatalyst in Aqueous Media: Toward a Solar-Assisted Water Disinfection System. , 1994, Environmental science & technology.

[35]  G. Aiken,et al.  Effects of humic substances on precipitation and aggregation of zinc sulfide nanoparticles. , 2011, Environmental science & technology.

[36]  Rachel Lubart,et al.  The Different Behavior of Rutile and Anatase Nanoparticles in Forming Oxy Radicals Upon Illumination with Visible Light: An EPR Study , 2012, Photochemistry and photobiology.

[37]  N. Blough,et al.  On the origin of the optical properties of humic substances. , 2004, Environmental science & technology.

[38]  Christine Ogilvie Robichaud,et al.  Estimates of upper bounds and trends in nano-TiO2 production as a basis for exposure assessment. , 2009, Environmental science & technology.

[39]  J. Gebicki,et al.  Proteins are major initial cell targets of hydroxyl free radicals. , 2004, The international journal of biochemistry & cell biology.

[40]  H. Bajaj,et al.  Photocatalytic Degradation of Methylene Blue Dye Using Ultraviolet Light Emitting Diodes , 2009 .

[41]  S. Provencher.  CONTIN: A general purpose constrained regularization program for inverting noisy linear algebraic and integral equations , 1984 .

[42]  Nathalie Tufenkji,et al.  Aggregation of titanium dioxide nanoparticles: role of a fulvic acid. , 2009, Environmental science & technology.

[43]  Lucinda F Buhse,et al.  Lack of significant dermal penetration of titanium dioxide from sunscreen formulations containing nano- and submicron-size TiO2 particles. , 2010, Toxicological sciences : an official journal of the Society of Toxicology.

[44]  Jing Li,et al.  Toxicity and internalization of CuO nanoparticles to prokaryotic alga Microcystis aeruginosa as affected by dissolved organic matter. , 2011, Environmental science & technology.

[45]  Yongsheng Chen,et al.  Mechanism of photogenerated reactive oxygen species and correlation with the antibacterial properties of engineered metal-oxide nanoparticles. , 2012, ACS nano.

[46]  Yuri Volkov,et al.  High-content screening as a universal tool for fingerprinting of cytotoxicity of nanoparticles. , 2008, ACS nano.

[47]  Stephen B Johnson,et al.  Adsorption of organic matter at mineral/water interfaces. IV. Adsorption of humic substances at boehmite/water interfaces and impact on boehmite dissolution. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[48]  F. Gagné,et al.  Ecotoxicity of selected nano‐materials to aquatic organisms , 2008, Environmental toxicology.

[49]  Wei Jiang,et al.  Bacterial toxicity comparison between nano- and micro-scaled oxide particles. , 2009, Environmental pollution.

[50]  K. Gray,et al.  Fabricating highly active mixed phase TiO2 photocatalysts by reactive DC magnetron sputter deposition , 2006 .

[51]  Navid B. Saleh,et al.  Titanium dioxide (P25) produces reactive oxygen species in immortalized brain microglia (BV2): implications for nanoparticle neurotoxicity. , 2006, Environmental science & technology.

[52]  S. Martin,et al.  Environmental Applications of Semiconductor Photocatalysis , 1995 .

[53]  M. Madigan,et al.  Brock Biology of Microorganisms , 1996 .

[54]  M. DeRosa.  Photosensitized singlet oxygen and its applications , 2002 .

[55]  Anthony P. Straub,et al.  Role of temperature and Suwannee River natural organic matter on inactivation kinetics of rotavirus and bacteriophage MS2 by solar irradiation. , 2011, Environmental science & technology.

[56]  The bactericidal effect of TiO2 photocatalysis involves adsorption onto catalyst and the loss of membrane integrity. , 2006, FEMS microbiology letters.

[57]  Qilin Li,et al.  Kinetics of C60 fullerene dispersion in water enhanced by natural organic matter and sunlight. , 2009, Environmental science & technology.

[58]  Jun Liu,et al.  Phototoxicity of nano titanium dioxides in HaCaT keratinocytes--generation of reactive oxygen species and cell damage. , 2012, Toxicology and applied pharmacology.

[59]  T. Hirano,et al.  Singlet Oxygen Generation Photocatalyzed by TiO2 Particles and Its Contribution to Biomolecule Damage , 2006 .

[60]  Mark R Wiesner,et al.  Comparison of the abilities of ambient and manufactured nanoparticles to induce cellular toxicity according to an oxidative stress paradigm. , 2006, Nano letters.

[61]  Kiril Hristovski,et al.  Occurrence and removal of titanium at full scale wastewater treatment plants: implications for TiO2 nanomaterials. , 2011, Journal of environmental monitoring : JEM.

[62]  N. Monteiro-Riviere,et al.  Limitations and relative utility of screening assays to assess engineered nanoparticle toxicity in a human cell line. , 2009, Toxicology and applied pharmacology.

[63]  B. Nowack,et al.  Exposure modeling of engineered nanoparticles in the environment. , 2008, Environmental science & technology.

[64]  N. Dimitrijević,et al.  The Effects of Pt Doping on the Structure and Visible Light Photoactivity of Titania Nanotubes , 2010 .

[65]  Jerzy Leszczynski,et al.  Using nano-QSAR to predict the cytotoxicity of metal oxide nanoparticles. , 2011, Nature nanotechnology.

[66]  M Boller,et al.  Synthetic TiO2 nanoparticle emission from exterior facades into the aquatic environment. , 2008, Environmental pollution.

[67]  Thilo Hofmann,et al.  Nanostructured TiO2: transport behavior and effects on aquatic microbial communities under environmental conditions. , 2009, Environmental science & technology.

[68]  S. Biju,et al.  Correlating Photoluminescence and Photocatalytic Activity of Mixed-phase Nanocrystalline Titania , 2009 .

[69]  Pedro J J Alvarez,et al.  Effect of natural organic matter on toxicity and reactivity of nano-scale zero-valent iron. , 2011, Water research.

[70]  Fubing Peng,et al.  High-throughput screening of silver nanoparticle stability and bacterial inactivation in aquatic media: influence of specific ions. , 2010, Environmental science & technology.

[71]  S. Traina,et al.  Adsorption of (poly)maleic acid and an aquatic fulvic acid by geothite , 1997 .

[72]  Chang Woo Kim,et al.  Preparation and characterization of the antibacterial Cu nanoparticle formed on the surface of SiO2 nanoparticles. , 2006, The journal of physical chemistry. B.

[73]  Christopher S. Foote,et al.  Active oxygen in chemistry , 1996 .

[74]  J. Hoigné.  Inter-calibration of OH radical sources and water quality parameters , 1997 .

[75]  Lutz Mädler,et al.  Stability, bioavailability, and bacterial toxicity of ZnO and iron-doped ZnO nanoparticles in aquatic media. , 2011, Environmental science & technology.

[76]  Kimberly A. Gray,et al.  Explaining the Enhanced Photocatalytic Activity of Degussa P25 Mixed-Phase TiO2 Using EPR , 2003 .

[77]  P. Baveye,et al.  Influence of ionic strength, pH, and cation valence on aggregation kinetics of titanium dioxide nanoparticles. , 2009, Environmental science & technology.

[78]  Marie Carrière,et al.  Size-, composition- and shape-dependent toxicological impact of metal oxide nanoparticles and carbon nanotubes toward bacteria. , 2009, Environmental science & technology.

[79]  N. Dimitrijević,et al.  Synthesizing mixed-phase TiO2 nanocomposites using a hydrothermal method for photo-oxidation and photoreduction applications , 2008 .

[80]  David A. Dana.  The Nanotechnology Challenge: Creating Legal Institutions For Uncertain Risks , 2014 .