TiO2 Engineered Nanoparticles Research Articles

Investigating the impact of TiO2 nanoparticles on bioactive compounds in sweet pepper seedlings: a comparison of foliar and root application methods

Engineered TiO2 nanoparticles (TiO2-NPs) are broadly produced and utilized in various consumer products. However, plant uptake of NPs may lead to disruptions in physiological and metabolic processes, particularly when the plant’s defense mechanisms are overwhelmed. In this study, sweet pepper seedlings were exposed to TiO2-NPs via foliar (2.5% suspension) and root (0.5% suspension) methods, with plants treated with distilled water serving as controls. Results showed that foliar application caused higher accumulation of Ti in leaves as compared to stems, while root exposure led to a higher increase of Ti content in stems than in leaves. Additionally, foliar application led to alterations in chemical composition of the plants, including changes in malondialdehyde (MDA), L-ascorbic acid, total phenolics content, carotenoids, in total antioxidant capacity (TAC) and antioxidant enzymes activity. Root exposure also affected enzyme activity and TAC, but also altered H2O2, MDA and glutathione content. Chlorophylls remained at stable level in the leaves of the seedlings. Overall, these studies provide important information on plant-nanoparticle interactions and the potential effects of different nanoparticle application strategies. These data indicate also that the specific nanoparticles, applied at a controlled manner, have potential to boost the plant metabolism and improve stress tolerance, which is an important factor affecting crops’ quality and productivity.

Visible light photocatalytic degradation of organic pollutants in industrial wastewater by engineered TiO2 nanoparticles

Visible light photocatalytic degradation of organic pollutants in industrial wastewater by engineered TiO2 nanoparticles

Finding Nano: Challenges Involved in Monitoring the Presence and Fate of Engineered Titanium Dioxide Nanoparticles in Aquatic Environments

In recent years, titanium dioxide (TiO2) has increasingly been used as an inorganic ultraviolet (UV) filter for sun protection. However, nano-TiO2 may also pose risks to the health of humans and the environment. Thus, to adequately assess its potential adverse effects, a comprehensive understanding of the behaviour and fate of TiO2 in different environments is crucial. Advances in analytical and modelling methods continue to improve researchers’ ability to quantify and determine the state of nano-TiO2 in various environments. However, due to the complexity of environmental and nanoparticle factors and their interplay, this remains a challenging and poorly resolved feat. This paper aims to provide a focused summary of key particle and environmental characteristics that influence the behaviour and fate of sunscreen-derived TiO2 in swimming pool water and natural aquatic environments and to review the current state-of-the-art of single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) approaches to detect and characterise TiO2 nanoparticles in aqueous media. Furthermore, it critically analyses the capability of existing fate and transport models to predict environmental TiO2 levels. Four particle and environmental key factors that govern the fate and behaviour of TiO2 in aqueous environments are identified. A comparison of SP-ICP-MS studies reveals that it remains challenging to detect and characterise engineered TiO2 nanoparticles in various matrices and highlights the need for the development of new SP-ICP-MS pre-treatment and analysis approaches. This review shows that modelling studies are an essential addition to experimental studies, but they still lack in spatial and temporal resolution and mostly exclude surface transformation processes. Finally, this study identifies the use of Bayesian Network-based models as an underexplored but promising modelling tool to overcome data uncertainties and incorporates interconnected variables.

Intra-laboratory assessment of a method for the detection of TiO2 nanoparticles present in sunscreens based on multi-detector asymmetrical flow field-flow fractionation

In this study, an intra-laboratory assessment was carried out to establish the effectiveness of a method for the detection of TiO2 engineered nanoparticles (ENPs) present in sunscreen containing nano-scale TiO2 and a higher nanometer-range (approx. 200–500 nm) TiO2, as well as iron oxide particles. Three replicate measurements were performed on five separate days to generate the measurement uncertainties associated with the quantitative asymmetrical flow field-flow fractionation (AF4) measurement of the hydrodynamic radius rh,mode1 (MALS), rh,mode1 (ICP-MS), rh,mode2 (ICP-MS), and calculated mass-based particle size distribution (d10, d50, d90). The validation study demonstrates that the analysis of TiO2 ENPs present in sunscreen by AF4 separation-multi detection produces quantitative data (mass-based particle size distribution) after applying the sample preparation method developed within the NanoDefine project with uncertainties based on the precision (uIP) of 3.9–8.8%. This method can, therefore, be considered as the method with a good precision. Finally, the bias data shows that the trueness of the method (ut = 5.5–52%) can only be taken as a proxy due to the lack of a sunscreen standard containing certified TiO2 ENPs.

Study on the characteristics of naturally formed TiO2 nanoparticles in various surficial media from China

To better understand the occurrence state and characteristics of naturally formed TiO2 in the environment, four types of different natural media were collected from nine areas distributed throughout five different provinces in China. For the first time, this study demonstrated that naturally formed TiO2 nanoparticles are widely distributed in various media (soil solid, underground water, geogas and organisms) on the surface of the earth. With the help of a high-resolution transmission electron microscope (TEM), the morphology, chemical composition and crystal structure of TiO2 nanoparticles in natural media were obtained. The characteristics of natural TiO2 nanoparticles were found to be different from those of engineered TiO2 nanoparticles, while natural TiO2 nanoparticles in different media were found to have similar characteristics. In general, single naturally formed TiO2 nanoparticles usually appear as complete or incomplete polygons, while aggregations of naturally formed TiO2 nanoparticle are mostly irregular in shapes. The main growth stages of TiO2 crystals in natural media were also investigated in this study. In brief, along with the crystal shapes of the TiO2 particles changing from imperfect to perfect, the degree of crystallinity of the particles was also gradually improved. Furthermore, natural TiO2 nanoparticles were found to always carry some amount of other elements related to the surrounding environment, resulting in a more complex composition. This phenomenon may contribute to the interpretation of elemental migration and ore prospecting to some degree, but the potential environmental hazards associated with TiO2 nanoparticles may be enhanced as well.

Fabrication of Engineered TiO2 Nanoparticles Their Cytotoxic, Genetic and Bioanalytical Study for Myoblast Cancer Cells

Fabrication of Engineered TiO₂ Nanoparticles Their Cytotoxic, Genetic and Bioanalytical Study for Myoblast Cancer Cells

Characterization of the Natural Colloidal TiO2 Background in Soil

An increasing amount of TiO2 engineered nanoparticles (TNP) is released into soils and sediments, increasing the need for dedicated detection methods. Titanium is naturally present in soils at concentrations typically much higher than the estimated concentrations for TNP. Therefore, a precise knowledge of this natural background, including the colloidal fraction, is required for developing adapted strategies for detecting TNP. In this study, we characterized the natural colloidal Ti-background by analyzing eight soils with different properties and origins. A combination of X-ray fluorescence analysis and ICP-OES was used for determining the silicate bound fraction, which was a minor fraction for all soils (0–32%). The colloidal fraction obtained by extracting colloids from soil prior to ICP-OES measurements ranged between 0.3% and 7%. Electron microscopy and hydrodynamic chromatography confirmed that Ti in the form of colloids or larger particles was mostly present as TiO2 minerals with a fraction smaller than 100 nm. The size distribution mode of the extracted colloids determined using hydrodynamic chromatography ranged between 80 and 120 nm. The chromatograms suggested a broad size distribution with a significant portion below 100 nm. In addition to these data, we also discuss possible implications of our findings for the method development for detecting TNP in soils.

Evaluation of four new studies on the potential toxicity of titanium dioxide used as a food additive (E171).

The European Commission requested EFSA to carry out a scientific evaluation on four studies on the potential toxicity of titanium dioxide (TiO2) used as a food additive (E 171) and to indicate whether they would merit re‐opening the existing opinion of EFSA on the safety of TiO2 (E 171) as a food additive. The results of the Bettini et al. (2017) study did not provide enough justification for a new carcinogenicity study, but, should additional useful mechanistic information become available, this could be reconsidered in future. The new in vitro findings in the Proquin et al. (2017) study did not modify the conclusion on the genotoxicity of TiO2 as stated in the previous EFSA opinion of 2016 on the safety of TiO2 (E 171) as a food additive. The effects of engineered TiO2 nanoparticles reported by the Guo et al. (2017) study were of uncertain biological significance and therefore of limited relevance for the risk assessment of the food additive TiO2 (E 171). There was significant uncertainty in the risk assessment performed by Heringa et al. (2016), which did not include a weight of evidence analysis of the whole database. The Panel considered that the four studies evaluated, highlighted some concerns but with uncertainties, therefore their relevance for the risk assessment was considered limited and further research would be needed to decrease the level of uncertainties. Overall, three of the studies, reporting that TiO2 induced various effects in in vitro and in vivo models, may be useful for hazard identification of TiO2. In the fourth study by Heringa et al. (2016), numerous assumptions were made, which resulted in large uncertainty in their conclusion. Altogether, the Panel concluded that the outcome of the four studies did not merit re‐opening the existing opinion of EFSA related to the safety of TiO2 (E 171) as a food additive.

Heteroaggregation of CeO2 and TiO2 engineered nanoparticles in the aqueous phase: Application of turbiscan stability index and fluorescence excitation-emission matrix (EEM) spectra

CeO2 and TiO2 engineered nanoparticles (ENPs) are being increasingly used in many applications. Due to their properties, heteroaggregation between these two types of ENPs is very likely, which can determine their fate and transport. However, the heteroaggregation behavior of CeO2 and TiO2 ENPs is still not clear, partly due to the lack of appropriate tools. In this study, we investigated the application of Turbiscan Stability Index (TSI) for the measurements of CeO2/TiO2 ENP heteroaggregation. TSI was found to be effective to investigate the heteroaggregation and stability of the CeO2-TiO2 ENPs system. Increasing CeO2/TiO2 ENPs ratio reduces the TSI values, indicating higher stability. Fluorescence excitation-emission matrix (EEM) spectra were used to study the interface interaction between humic acid (HA) and CeO2/TiO2 ENPs. The TSI value of ENPs were rising with the increasing of CeO2/TiO2 ENPs ratios in the H River or Q Reservoir water. In addition, their variation trends were similar to those in well-controlled synthetic water. Proposed interaction mechanisms include surface charge attraction and competitive adsorption.

Optimisation of an extraction/leaching procedure for the characterisation and quantification of titanium dioxide (TiO2) nanoparticles in aquatic environments using SdFFF-ICP-MS and SEM-EDX analyses

A novel, optimized and validated extraction method for engineered TiO2 nano-particles from environmental samples prior to SdFFF-MALS-ICP-MS/MS analysis is presented.

Methodological considerations for using umu assay to assess photo-genotoxicity of engineered nanoparticles

In this study we investigated the feasibility of high-throughput (96-well plate) umu assay to test the genotoxic effect of TiO2 engineered nanoparticles (ENPs) under UV light (full spectrum) and visible light (455nm). Exposure of TiO2 ENPs to up to 60min of UV light induced a photocatalytic production of ROS. However, UV light itself caused cytotoxic damage to Salmonella typhimurium at exposures >15min and a genotoxic effect at exposures >0.5min; and use of UV filters did not lower this effect. No genotoxicity of TiO2 ENPs was observed under visible light conditions at concentrations up to 100μgmL−1; or under dark conditions at concentrations up to 667μgmL−1, though cytotoxicity was seen at the higher concentrations. Additionally, the growth factor calculation was influenced by a shading effect due to ENPs, and was corrected by considering the pre-incubation OD readings of Plate B. Recommendations provided in this paper, as well as investigation of the effect of the light sources should be considered when using the umu assay to quantify the photo-genotoxicity of engineered nanomaterials.

Environmental applications and implications of nanotechnologies

Since the launch of the U.S. National Nanotechnology Initiative (NNI) in 2000, research and development in nanotechnology innovation has come a long way worldwide. Based on the Web of Science database, the total SCIindexed papers surged from 971 in 2000 to 13, 546 in 2014, and the momentum remains strong. One of the most active and productive research fields has been environmental applications and implications of nanomaterials and nanotechnologies. Environmental nanotechnologies have shown great potential to fundamentally change the conventional practices in environmental cleanup. While the development of innovative cleanup technologies continues to evolve, our understanding of the environmental implications/impacts associated with the booming applications of nanotechnologies in various fields has also deepened. The objectives of this special issue were to: 1) promote exchanges of ideas and information on the latest development of environmental nanotechnologies, 2) facilitate development of more cost-effective and “greener” cleanup technologies based on innovative nanomaterials and nanotechnologies, 3) address limitation and potential environmental impacts of nanotechnologies and nanomaterials, and 4) identify major knowledge gaps and research directions. Due to the capacity limit, we can only include 20 papers in this issue from a large pool of high-quality submissions, including 14 research papers addressing applications, four papers on environmental impacts/implications, and two critical review papers. The applications are focused on adsorption, and redox or catalytic degradation of contaminants in water and potentially in soil. The nanomaterials encompass carbonaceous nanomaterials including carbon nanotubes, hydroxyapatite, metal oxides, zero-valent metals including iron, metal catalysts, iron-carbon composite microspheres, and TiO2 nanotubes. The implication papers address interactions of carbonaceous materials with wastewater biomass, effects of zinc oxide on soil microorganisms, effects of nano-silicon on lead in rice cultivars, and toxicity of engineered TiO2 nanoparticles, whereas the critical reviews thoroughly examine applications of nano-sized magnetite and hollow nanomaterials. While most of these works deal with water treatment, it appears that more research is needed to develop novel in situ nanotechnologies for remediation of soil and groundwater and to address impacts of nanoparticles in the subsurface on the biogeochemical conditions. As environmental nano-research continues to thrive, we hope this special issue will inspire even greater innovation and discoveries in the field. We thank all authors, reviewers, and the editorial staff of FESE for their time and contributions to this issue. In particular, we are grateful to Professor Xia Huang for her support and meticulous guidance throughout the process.

Simplified TiO2 force fields for studies of its interaction with biomolecules

Engineered TiO2 nanoparticles have been routinely applied in nanotechnology, as well as in cosmetics and food industries. Despite active experimental studies intended to clarify TiO2's biological effects, including potential toxicity, the relation between experimentally inferred nanotoxicity and industry standards for safely applying nanoparticles remains somewhat ambiguous with justified concerns. Supplemental to experiments, molecular dynamics simulations have proven to be efficacious in investigating the molecular mechanism of a biological process occurring at nanoscale. In this article, to facilitate the nanotoxicity and nanomedicine research related to this important metal oxide, we provide a simplified force field, based on the original Matsui-Akaogi force field but compatible to the Lennard-Jones potentials normally used in modeling biomolecules, for simulating TiO2 nanoparticles interacting with biomolecules. The force field parameters were tested in simulating the bulk structure of TiO2, TiO2 nanoparticle-water interaction, as well as the adsorption of proteins on the TiO2 nanoparticle. We demonstrate that these simulation results are consistent with experimental data/observations. We expect that simulations will help to better understand the interaction between TiO2 and molecules.

A multi-integrated approach on toxicity effects of engineered TiO2 nanoparticles

The new properties of engineered nanoparticles drive the need for new knowledge on the safety, fate, behavior and biologic effects of these particles on organisms and ecosystems. Titanium dioxide nanoparticles have been used extensively for a wide range of applications, e.g, self-cleaning surface coatings, solar cells, water treatment agents, topical sunscreens. Within this scenario increased environmental exposure can be expected but data on the ecotoxicological evaluation of nanoparticles are still scarce. The main purpose of this work was the evaluation of effects of TiO2 nanoparticles in several organisms, covering different trophic levels, using a battery of aquatic assays. Using fish as a vertebrate model organism tissue histological and ultrastructural observations and the stress enzyme activity were also studied. TiO2 nanoparticles (Aeroxide® P25), two phase composition of anatase (65%) and rutile (35%) with an average particle size value of 27.6±11 nm were used. Results on the EC50 for the tested aquatic organisms showed toxicity for the bacteria, the algae and the crustacean, being the algae the most sensitive tested organism. The aquatic plant Lemna minor showed no effect on growth. The fish Carassius auratus showed no effect on a 21 day survival test, though at a biochemical level the cytosolic Glutathione-S-Transferase total activity, in intestines, showed a general significant decrease (p<0.05) after 14 days of exposure for all tested concentrations. The presence of TiO2 nanoparticles aggregates were observed in the intestine lumen but their internalization by intestine cells could not be confirmed.

The influence of natural organic matter and aging on suspension stability in guideline toxicity testing of silver, zinc oxide, and titanium dioxide nanoparticles with Daphnia magna

The present study investigated changes in suspension stability and ecotoxicity of engineered nanoparticles (ENPs) by addition of Suwannee River natural organic matter and aging of stock and test suspensions prior to testing. Acute toxicity tests of silver (Ag), zinc oxide (ZnO), and titanium dioxide (TiO2 ) ENPs with Daphnia magna were carried out following Organisation for Economic Co-operation and Development test guidelines. Daphnia magna was found to be very sensitive to Ag ENPs (48-h 50% effective concentration 33 μg L(-1) ), and aging of the test suspensions in M7 medium (up to 48 h) did not decrease toxicity significantly. Conversely, the presence of Suwannee River natural organic matter (NOM; 20 mg L(-1) ) completely alleviated Ag ENP toxicity in all testing scenarios and did not aid in stabilizing suspensions. In contrast, addition of Suwannee River NOM stabilized ZnO ENP suspensions and did not decrease toxicity. Aging for 48 h generated monotonous concentration-response curves in the presence and absence of Suwannee River NOM. At concentrations up to 100 mg L(-1) TiO2 ENPs did not cause immobilization of D. magna under any of the tested conditions. Presence of Suwannee River NOM caused agglomeration in stock suspensions. The authors' results suggest that aging and presence of Suwannee River NOM are important parameters in standard toxicity testing of ENPs, which in some cases may aid in gaining better control over the exposure conditions but in other cases might contribute to agglomeration or elimination of ENP toxicity. Therefore, modifications to the current guidelines for testing ENPs should be evaluated on a case-by-case basis. Environ Toxicol Chem 2015;34:497-506. © 2014 SETAC.

Isothermal titration calorimetry as a powerful tool to quantify and better understand agglomeration mechanisms during interaction processes between TiO2 nanoparticles and humic acids

Association processes between engineered TiO2 nanoparticles and Suwannee River humic acids are investigated by isothermal titration calorimetry.

Comparison of the Aggregation Behavior of TiO2 Nanoparticles Exposed to Fulvic Acid and Bacillus subtilis Exudates

The objective of this study was to compare the relative impact of humic and non-humic natural organic matter (NOM) on the aggregation behaviors of engineered TiO2 nanoparticles (nano-TiO2). After exposure of nano-TiO2 to varying concentrations of Suwannee River fulvic acid (SRFA) and Bacillus subtilis exudate in high and low ionic strength (IS) solutions at pH 3 to pH 7.5, aggregation behaviors were evaluated via dynamic light scattering (DLS) measurements and sedimentation studies. Although pH, IS, and NOM concentration exerted strong controls on nano-TiO2 aggregation behaviors, suspensions exposed to either SRFA or bacterial exudate at normalized dissolved organic carbon (DOC) concentrations exhibited remarkably similar behaviors. In high IS systems, nano-TiO2 exposed to either SRFA or bacterial exudate sedimented rapidly, except in the presence of high NOM concentrations at pH 6 and 7.5. Low IS treatments exhibited a larger range of effects. In fact, relative to NOM-free controls, nano-TiO2 aggregates in SRFA and bacterial exudate exposures sedimented up to 14 times faster at pH 3 and up to 13 times slower at pH 7.5. Adsorption of organic molecules onto nano-TiO2 can enhance aggregation via colloidal bridging and/or charge neutralization, or with more complete surface coverage, can diminish aggregation via electrostatic repulsion and/or steric hindrance. Collectively, these data suggest that solution pH, IS, and NOM concentration, and to a lesser extent NOM origin, can control the fate and mobility of nano-TiO2 in geologic systems.

Toxicity of nanoparticles embedded in paints compared with pristine nanoparticles in mice.

The unique physical and chemical properties of nanomaterials have led to their increased use in many industrial applications, including as a paint additive. For example, titanium dioxide (TiO2) engineered nanoparticles (ENPs) have well-established anti-UV, self-cleaning, and air purification effects. Silver (Ag) ENPs are renowned for their anti-microbial capabilities and silicon dioxide (SiO2) ENPs are used as fire retardants and anti-scratch coatings. In this study, the toxic effects and biodistribution of three pristine ENPs (TiO2, Ag, and SiO2), three aged paints containing ENPs (TiO2, Ag, and SiO2) along with control paints without ENPs were compared. BALB/c mice were oropharyngeally aspirated with ENPs or paint particles (20 μg/aspiration) once a week for 5 weeks and sacrificed either 2 or 28 days post final aspiration treatment. A bronchoalveolar lavage was performed and systemic blood toxicity was evaluated to ascertain cell counts, induction of inflammatory cytokines, and key blood parameters. In addition, the lung, liver, kidney, spleen, and heart were harvested and metal concentrations were determined. Exposure to pristine ENPs caused subtle effects in the lungs and negligible alterations in the blood. The most pronounced toxic effects were observed after Ag ENPs exposure; an increased neutrophil count and a twofold increase in pro-inflammatory cytokine secretion (keratinocyte chemoattractant (KC) and interleukin-1ß (IL-1ß)) were identified. The paint containing TiO2 ENPs did not modify macrophage and neutrophil counts, but mildly induced KC and IL-1ß. The paints containing Ag or SiO2 did not show significant toxicity. Biodistribution experiments showed distribution of Ag and Si outside the lung after aspiration to respectively pristine Ag or SiO2 ENPs. In conclusion, we demonstrated that even though direct exposure to ENPs induced some toxic effects, once they were embedded in a complex paint matrix little to no adverse toxicological effects were identified.

Life-cycle assessment of engineered nanomaterials: a literature review of assessment status

The potential environmental impacts of engineered nanomaterials (ENMs), and their engineered nanoparticles (ENPs), have, in recent years, been a cause of concern. Life-cycle assessment (LCA) is a highly qualified tool to assess products and systems and has an increasing extent been applied to ENMs. However, still only 29 case studies on LCA of ENMs have been published in journals and this article investigates these studies. Generally, data on production of ENMs as well as the coverage of the life cycle are limited. In particular, within use and disposal stages data are scarce due to many unknowns regarding the potential release and fate of ENMs/ENPs to and in the environment. This study investigates the sensitivity of case studies with respect to ecotoxicity impacts through a quantification of the potential ecotoxicity impacts to algae, daphnia and fish as a result of direct release of Ag and TiO2 ENPs (mainly <200 nm in nominal diameter size) from various ENM products to the freshwater compartment. It was found that Ag and TiO2 release, from 1 g Ag or TiO2 ENM product, poses up to ca. 3.5 orders of magnitude higher ecotoxicity impact than the production of 1 g polymer (PP, PE and PET average) or 1 Wh of grid mix electricity from Scandinavia. ENMs from Ag had higher ecotoxic impact than those from TiO2 and there was a linear regression between Ag ENM content in the considered products and the potential ecotoxicity impacts to the freshwater species, according to release of total Ag during use (mainly washing).

Fate of pristine TiO2 nanoparticles and aged paint-containing TiO2 nanoparticles in lettuce crop after foliar exposure

Engineered TiO2 nanoparticles (TiO2-NPs) are present in a large variety of consumer products, and are produced in largest amount. The building industry is a major sector using TiO2-NPs, especially in paints. The fate of NPs after their release in the environment is still largely unknown, and their possible transfer in plants and subsequent impacts have not been studied in detail. The foliar transfer pathway is even less understood than the root pathway. In this study, lettuces were exposed to pristine TiO2-NPs and aged paint leachate containing TiO2-NPs and microparticles (TiO2-MPs). Internalization and in situ speciation of Ti were investigated by a combination of microscopic and spectroscopic techniques. Not only TiO2-NPs pristine and from aged paints, but also TiO2-MPs were internalized in lettuce leaves, and observed in all types of tissues. No change in speciation was noticed, but an organic coating of TiO2-NPs is likely. Phytotoxicity markers were tested for plants exposed to pristine TiO2-NPs. No acute phytotoxicity was observed; variations were only observed in glutathione and phytochelatin levels but remained low as compared to typical values. These results obtained on the foliar uptake mechanisms of nano- and microparticles are important in the perspective of risk assessment of atmospheric contaminations.