Ti Accumulation Research Articles

Influences of TiO2 nanoparticle and fipronil co-exposure on metabolite profiles in mouse intestines.

Food contaminates, such as insecticide, may influence the toxicity of nanoparticles (NPs) to intestine. The present study investigated the combined toxicity of TiO2 NPs and fipronil to male mouse intestine. Juvenile mice (8weeks) were orally exposed to 5.74 mg/kg TiO2 NPs, 2.5mg/kg fipronil, or both, once a day, for 5days. We found that both TiO2 NPs and fipronil induced some pathological changes in intestines, accompanying with defective autophagy, but these effects were not obviously enhanced after TiO2 NP and fipronil co-exposure. Fipronil promoted Ti accumulation but induced minimal impact on other trace elements in TiO2 NP-exposed intestines. Metabolomics data revealed that the exposure altered metabolite profiles in mouse intestines, and two KEGG pathways, namely, ascorbate and aldarate metabolism (mmu00053) and glutathione metabolism (mmu00480), were only statistically significantly changed after TiO2 NP and fipronil co-exposure. Five metabolites, including 2-deoxy-D-erythro-pentofuranose 5-phosphate, 5alpha-cholestanol, beta-D-glucopyranuronic acid, elaidic acid, and isopentadecanoic acid, and maltotriose, were more significantly up-regulated after the co-exposure, whereas trisaccharide and xylonolactone were only significantly down-regulated by the co-exposure. We concluded that fipronil had minimal impact to enhance the toxicity of TiO2 NPs to mouse intestines but altered metabolite profiles.

Tuning electrolyte aging in titanium anodization to fabricate nano-engineered implants

Anodization is well researched to nano-engineer Ti to fabricate TiO2 nanotubes/nanopores for varied applications, including biomedical implants. For the fabrication of reproducible and stable nanotubes/nanopores, the use of aged (few hours used) organic electrolyte to anodize Ti is recognized and practised. However, the electrolyte aging phenomenon remains poorly understood. In this study, we tune anodization voltage, time and anode area, to categorically understand the influence of each in electrolyte aging that fabricates robust and ordered titania nanopores (TNPs) on micro-rough Ti. Briefly, various aged electrolytes were used to fabricate TNPs on micro-rough Ti that were characterized (topography, roughness, hydrophilicity, mechanical strength and protein adhesion capacity) to determine the most influential electrolyte aging conditions. The study revealed that increased Ti-anode size, anodization voltage and time during aging contribute to enhanced free F consumption and Ti accumulation in the electrolytes, reducing their conductivity. Ideal electrolyte aging characteristics including Ti/F ion concentration and conductivity range were identified to aid in single-step electrolyte aging that yielded well-ordered TNPs with desirable wettability and protein adhesion capacity, representing favorable implant modification. This electrolyte aging optimization paves the way for future advances in this domain.

Maternal, placental, and fetal distribution of titanium after repeated titanium dioxide nanoparticle inhalation through pregnancy

Epidemiological studies have associated ambient engineered nanomaterials or ultrafine particulate matter (PM0.1), collectively referred to as nanoparticles (NPs), with adverse pregnancy outcomes including miscarriage, preterm labor, and fetal growth restriction. Evidence from non-pregnant models demonstrate that NPs can cross the lung air-blood barrier and circulate systemically. Therefore, inhalation of NPs during pregnancy leading to fetoplacental exposure has garnered attention. The purpose of this study was to evaluate the distribution of inhaled titanium dioxide nanoparticles (nano-TiO2) from the maternal lung to maternal and fetal systemic tissues. Pregnant Sprague Dawley rats were administered whole-body exposure to filtered air or of nano-TiO2 aerosols (9.96 ± 0.06 mg/m3) between gestational day (GD) 4 and 19. On GD 20 maternal, placental, and fetal tissues were harvested then digested for ICP-MS analysis to measure concentrations of titanium (Ti). TEM was used to visualize particle internalization by the placental syncytium. The results demonstrate the extrapulmonary distribution of Ti to various maternal organs during pregnancy. Our study found Ti accumulation in the decidua/junctional and labyrinth zones of placentas embedded in all sections of uterine horns. Further, NPs deposited in the placenta, identified by TEM, were found intracellularly within nuclear, endoplasmic reticulum, and vesicle organelles. This study identified the systemic distribution and placental accumulation of Ti after nano-TiO2 aerosol inhalation in a pregnancy model. These findings arouse concerns for poor air quality for pregnant women and possible contributions to adverse pregnancy outcomes.

Spectrometric Analysis of the Wear from Metallic and Ceramic Dental Implants following Insertion: An In Vitro Study.

Titanium wear is a growing area of interest within dental implantology. This study aimed to investigate titanium and zirconium wear from dental implants at the time of insertion using X-ray-fluorescence spectrometry (XRF) and an in vitro protocol utilizing artificial bovine bone plates. Five groups were analyzed using XRF-spectrometry: groups 1–4 (titanium implants) and group 5 (zirconia implants). The implants were inserted into two bone blocks held together by a vice. The blocks were separated, and the insertion sites were analyzed for titanium (Ti) and zirconium (Zr). Statistical descriptive analyses of Ti and Zr concentrations in the coronal, middle and apical bone interface were performed. A comparative analysis confirmed differences between the implant’s surface stability and Ti accumulation within the insertion sites of the bone block. There was a direct relationship between implant length and the quantity of titanium found on the bone block. The data generally indicates greater quantities of titanium in the coronal thirds of the implants, and less in the apical thirds. The titanium and zirconium found in the bone samples where the group 5 implants were inserted was not of statistical significance when compared to control osteotomies. The results of this study confirm wear from metallic, but not ceramic, dental implants at the time of insertion.

The Influence of Long-Term Dietary Intake of Titanium Dioxide Particles on Elemental Homeostasis and Tissue Structure of Mouse Organs.

Background: Titanium dioxide (TiO₂), consisting of nanoparticles and sub-microparticles, were widely used as food additive and consumed by people every day, which has aroused a public safety concern. Some studies showed TiO₂ can be absorbed by intestine and then distributed to different tissues after oral intake, which is supposed to affect the content of various elements in the body whereas led to tissue damage. However, knowledge gaps still exist in the impact of TiO₂ on the disorder of elemental homeostasis. Thus, this study aimed to explore the oral toxicity of TiO₂ by assessing its influence on elemental homeostasis and tissues injury. Method: ICR mice were fed with normal feed, TiO₂ nanoparticles (NPs)-mixed feed or TiO₂ submicron particles (MPs)-mixed feed (1% mass fraction TiO₂ NPs or MPs were mixed in commercial pellet diet) for 1, 3, and 6 months. Particles used in this study were characterized. The distribution of Ti and other 23 elements, the correlation among elements, and pathological change in the liver, kidney, spleen and blood cells of the mice was determined. Result: Ti accumulation only appeared in blood cells of mice treated with TiO₂ MPs-mixed feed for 6 months, but TiO₂ cause 12 kinds of elements (boron, vanadium, iron, cobalt, copper, zinc, selenium, sodium, calcium, magnesium, silicon, phosphorus) content changed in organ tissue. The changed kinds of elements in blood cells (6 elements), liver (7 elements) or kidney (6 elements) were more than in the spleen (1 element). The TiO₂ NPs induced more elements changed in blood cells and liver, and the TiO₂ MPs induced more elements changed in kidney. Significantly positive correlation between Ti and other elements was found in different organs except the liver. Organ injuries caused by TiO₂ NPs were severer than TiO₂ MPs. Liver exhibited obvious pathological damage which became more serious with the increase of exposure time, while kidney and spleen had slight damages. Conclusion: These results indicated long-time dietary intake of TiO₂ particles could induce element imbalance and organ injury. The liver displayed more serious change than other organs, especially under the treatment with TiO₂ NPs. Further research on the oral toxicity of TiO₂ NPs should pay more attention to the health effects of element imbalances using realistic exposure methods.

Divergence in response of japonica and hybrid rice to titanium dioxide nanoparticles

The present study aimed to compare the responses of two rice cultivars to titanium dioxide nanoparticles (nTiO2), in plant performance and root-associated soil microbes, and provide a reference for the selection of nanoparticle-responsive varieties. The field experiment was conducted to study the effects of nTiO2 (applied at 200 mg/kg) on typical Chinese rice cultivars, Wuyunjing23 (WYJ23) and Yongyou2640 (YY2640), for the whole life cycle. We evaluated agronomic and physiological parameters including chlorophyll content and antioxidant enzyme activities at the heading stage, and biomass, Ti, and nutrient elements uptake after harvest. Soil bacterial communities were also measured through 16S rRNA gene sequencing. Exposure to nTiO2 led to neither Ti accumulation nor changed biomass in either cultivar, but it increased root Fe uptake and reduced grain Cu content. Specifically, nTiO2 exposure decreased the chlorophyll content but increased the peroxidase activity in WYJ23; such altered physiology might affect root exudates and further modify bacterial communities. Although nTiO2 did not induce visible phytotoxicity in YY2640, it affected the abundance of bacteria genera associated with N turnover and plant-C-metabolizing (e.g., Geobacter and Gaiella), resulting in changed C and N cycling in the rhizosphere. This study revealed divergent responses of WYJ23 and YY2640 to nTiO2, both in plant physiology and rhizosphere system. nTiO2 induced greater physiological response but affected the rhizosphere little in WYJ23. By contrast, nTiO2 changed soil microbes and enzyme activities without affecting the physiology of YY2640, suggesting its superior adaptivity to nTiO2.

Toxicity of orally administered food-grade titanium dioxide nanoparticles.

This year, France banned the application of titanium dioxide nanoparticles as a food additive (hereafter, E171) based on the insufficient oral toxicity data. Here, we investigated the subchronic toxic responses of E171 (0, 10, 100, and 1,000 mg/kg) and tried to elucidate the possible toxic mechanism using AGS cells, a human stomach epithelial cell line. There were no dose-related changes in the Organisation for Economic Cooperation and Development test guideline-related endpoints. Meanwhile, E171 deeply penetrated cells lining the stomach tissues of rats, and the IgM and granulocyte-macrophage colony-stimulating factor levels were significantly lower in the blood from rats exposed to E171 compared with the control. The colonic antioxidant protein level decreased with increasing Ti accumulation. Additionally, after 24-h exposure, E171 located in the perinuclear region of AGS cells and affected expression of endoplasmic reticulum stress-related proteins. However, cell death was not observed up to the used maximum concentration. A gene profile analysis also showed that immune response-related microRNAs were most strongly affected by E171 exposure. Collectively, we concluded that the NOAEL of E171 for 90 days repeated oral administration is between 100 and 1,000 mg/kg for both male and female rats. Additionally, further study is needed to clarify the possible carcinogenesis following the chronic accumulation in the colon.

Distribution of TiO2 Nanoparticles in Acidic and Alkaline Soil and Their Accumulation by Aspergillus niger

The nanoparticles of TiO2 (TiO2 NP) have been used as a plant-growth stimulant or catalyst in pesticide formulas. However, due to high resistance of TiO2 NP to abiotic weathering, dissolved Ti is unlikely to act as an active compound in these preparations. Even if soil is acidic, TiO2 NP do not dissolve easily and preferably remain as undissolved particles. The low dissolution rates of inorganic nanoparticles in the soil environment make Ti in TiO2 NP largely unavailable for plants and soil microorganisms. To characterize the behavior of TiO2 NP in soil under different pH conditions, we analyzed TiO2 NP-size distribution in two soil materials, an alkaline and acidic one. We also cultivated Aspergillus niger, a fungus ubiquitously found in soils, in the growth medium spiked with TiO2 NP to assess accumulation of the nanoparticles in fungus. In soil suspensions, the dissolved Ti was present in low concentrations (up to 0.010 mg L−1). Most of the TiO2 NP remained in particulate form or appeared as aggregates sized 100–450 nm. In experiment on Ti accumulation by A. niger, TiO2 NP either settled down to the bottom of the flask with growth medium or were actually accumulated by the fungus; about 7.5% of TiO2 NP were accumulated in fungal mycelia. Most of the TiO2 NP remain in particulate form in soil solutions, regardless of soil pH. Filamentous fungus A. niger has the ability to accumulate bioavailable TiO2 NP, which hints at the possibility that some soil fungi can affect spatial distribution of this type of nanoparticles in soils.

Phytoremediation: Data on effects of titanium dioxide nanoparticles on phytoremediation of antimony polluted soil

This data article presents effects of titanium dioxide nanoparticles (TiO2 NPs) on phytoremediation of antimony contaminated soil using S. Bicolor in detail. Seedlings of S. bicolor were exposed to different doses of TiO2 NPs (0,50,100,250,500 and 1000 mg/kg) in plastic pots containing Sb-contaminated soil and cultivated over a 80-day period in a greenhouse. Harvested plants were dried in an oven at 70 °C for 48 h to obtain dry weight of the biomass. The concentrations of metal(loid)s in soil as well as in plant organs were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Chlorophyll contents of fresh leaves materials were measured by UV spectrophotometry at 645 nm and 663 nm. Data on distribution of Sb and Ti in roots and shoots of S. bicolor contaminated soil treated with different levels of TiO2 NPs are indicated in tables. Figures presented the data on plant growth behavior, Sb and Ti accumulation capacities, and physiological response of S. Bicolor in various treatments. The presented data are beneficial to gain insight into phytoremediation potential of S. bicolor in Sb-contaminated soil as well as plant behavior under the stress of both Sb and TiO2 NPs in soil. These data are useful for environmental researchers, soil and plant scientists, nanotechnology experts, stakeholders and decision-makers involved in soil decontamination challenges.

Geochemistry and secular trends in the middle–late Permian karst bauxite deposits, northwestern Iran

This study focuses on the middle–late Permian bauxite deposits found within karstic depressions and sinkholes of carbonates of the Ruteh and Nessen Formations, northwestern Iran. Data concerning five karst bauxite deposits, each related to a different stratigraphic position within the bedrock, were selected to address the chemical distribution and inter-elemental relationships, especially for critical elements, factors that control bauxite formation, and the parental affinity. The analyzed samples, mainly clayey bauxite and bauxitic clay, are characterized by large compositional fluctuations involving both major and trace elements. The major element composition is dominated by SiO2, TiO2, Al2O3, and Fe2O3. Among the critical elements, compositional fluctuations induce the occurrence of outliers for Co, Nb, Ta, LREE, and HREE, similar to other trace elements, such as Ba, Sr, Cr, U, and Zr. Elemental mobility indicates that most of elements are generally depleted. Among the critical elements, Co is enriched only in several samples of the older deposits, and ΣREE are enriched in some samples of the younger deposits. Factor analysis suggests that, due to the observed Al–Ga covariance, fairly acidic conditions were never attained during bauxitization, and that detrital resistant minerals concentrated during a bauxitization stage, promoting Al–Ti accumulation. Furthermore, the U co-variance with low soluble elements (Nb, Ta, and Th) suggests that U was mostly conservative during the formation of deposits. Cobalt co-varies with Cr, and these elements accumulated during later bauxitization stages, when the massive leaching of silica occurred. The CIA, CIW, and PIA paleo-weathering proxies indicate an upward weathering increase, which suggests a trend toward more extreme weathering conditions in a wetter and warmer climate, according to the Permian global warming. This is consistent with an upward increasing Ba/Sr ratio and the inspection of the A–CN–K plot, where the younger deposits fall close to the A–K edge, involving a clayey precursor requires a rainfall increase. Interestingly, the upward trend toward a warmer and wetter climate was also coupled with paleo-redox conditions promoting cerium oxidation, as depicted by the Ce/Ce* values. Finally, the Eu anomaly and the Sm/Nd ratio indicate that the studied bauxite deposits were mainly derived from a mafic protolith that formed in the middle–late Permian, as a consequence of the volcanism that affected the entire Iranian platform. A cluster of karst bauxites, however, has Eu/Eu* values lower than the average-standard deviation range of the mafic rocks, suggesting a possible contribution of a more differentiated and less mafic protolith. Similarly, the U/Th ratio, at large, supports the hypothesis of a mafic protolith for the middle–late Permian bauxite deposits, although some samples show the U/Th values well above the average-standard deviation range of the mafic rocks, likely indicating that processes promoting the accumulation of resistant minerals with high U/Th ratios cannot be excluded. This means that, in this case, the U/Th ratio does not necessarily reflect the protolith of karst bauxites and that, more in general, this proxy needs to be carefully interpreted when used to assess the parental affinity of residual rocks.

Anthropogenic Release and Distribution of Titanium Dioxide Particles in a River Downstream of a Nanomaterial Manufacturer Industrial Site

Several industries manufacture and process large quantities of engineered nanomaterials, thus increasing the potential for their environmental release during waste management and disposal. Herein, we quantified the release and spatial distribution of titanium dioxide nanomaterials (TiO2 NMs) emitted from an industrial waste stream that flows into a nearby river. Two sampling campaigns were carried out on the river in fall 2017 and spring 2018 at selected sites upstream and downstream of the Industrial Effluent and an urban wastewater treatment plant (WWTP). Significant Ti accumulation was detected in the sediments at the Industrial Effluent and WWTP sites for both fall and spring samples, with measured Ti concentrations of 75–193 mg Ti/kg reaching 21–55× that of the local background upstream. X-ray diffraction analysis confirmed the anatase and rutile mineralogy of the inputs. River surface waters were filtered on-site to distinguish between particulate (>0.20 μm), colloidal (0.02–0.20 μm), and dissolved and/or small nanoparticulate (NP) ( 0.20 μm), and that the particles sediment rapidly near the emission source and accumulate in the sediment.

Effect of chronic toxicity of the crystalline forms of TiO2 nanoparticles on the physiological parameters of Daphnia magna with a focus on index correlation analysis

The widespread use of titanium dioxide nanoparticles (NPs) and their inevitable release into aquatic environments have caused great concerns about their ecotoxicity. However, the chronic toxicity to TiO2 NPs of aquatic organisms has not been fully understood. In particular, research is lacking on the influence of the crystalline forms of TiO2 NPs on their mechanisms of toxicity. This study investigated the chronic toxicity (i.e., 21-day toxicity tests) of 5 types of TiO2 NPs with various percentages of crystalline forms on Daphnia magna. Results revealed that the crystalline form composed of 80% anatase and 20% rutile (i.e., the M1 form) had the highest energy band gap (i.e., Eg, the energy interval between the valence band edge and the conduction band edge) and caused maximal D. magna mortality compared with other crystalline forms. The crystalline form comprising 100% rutile (i.e., the R–S form) had the lowest Eg and exhibited a minimal effect on the physiological parameters of D. magna. Moreover, in a suitable environment without TiO2 NPs, D. magna progenies could recover to a normal physiological level (e.g., the mortalities of D. magna progenies were lower than those of parental D. magna that were exposed to TiO2 NPs at a concentration of 0.5 mg/L). Correlation analysis revealed that the body length, time of first brood, and number of neonates in the first brood of D. magna were negatively correlated with titanium accumulation in vivo. Furthermore, the indices of Ti accumulation and the product of Eg and Ti accumulation (i.e., Eg × Ti accumulation) were positively correlated (p < 0.05) with D. magna mortality, thus indicating that crystalline forms with a high Eg may cause severe toxicity to aquatic organisms at the same TiO2 bioaccumulation level.

The effects of Mg doping on the microstructure and transport properties of internal tin-processed brass matrix Nb3Sn superconductors

The addition of Zn into Cu matrix has been proved to enhance the Sn activity and accelerate the formation of a Nb3Sn layer in internal tin-processed Nb3Sn wires. However, in our samples, Ti is doped in Sn cores, and during the reaction, Ti was observed to accumulate between the inner and outer sub-elements of the 1980-Nb-core multi-filamentary brass matrix wires. With the addition of Mg into the brass matrix, Ti accumulation between the sub-elements was significantly suppressed, which promoted Ti incorporation into the Nb3Sn layers. Meanwhile, the formed Nb3Sn layers exhibited smaller grain sizes. Compared to the brass (Cu-12wt%Zn) matrix wires, an improvement of critical current density (Jc) was found in the Cu-12Zn-0.2Mg matrix wires due to the incorporation of Ti into the Nb3Sn layer and the refinement of the Nb3Sn grain size. The irreversibility field (Birr) and maximum bulk pinning forces (Fp,max) were calculated from the Kramer plot by analyzing the Jc(B) curves. A small amount of Mg (0.2 wt%) doping into the Cu-12Zn matrix wires can increase the Birr value by about 0.5 T and the Fp,max value by about 3 ∼ 4 GN m−3 after the wires were heat treated between 670 °C and 730 °C. The non-Cu Jc of the Cu-12Zn-0.2Mg matrix wires reaches the maximum value of 1533 A mm−2 @12 T after heat treatment at 685 °C and decreases at higher temperatures.

Evidences of metabolic alterations and cellular damage in mussels after short pulses of Ti contamination

Mytilus galloprovincialis mussels were exposed to seawater contaminated with Ti. Initial concentrations were 4.1, 32, and 66 μg L−1 that declined during the first 24 h of the experiments, and after 48 h values were <2 μg L−1. Experiments were run in triplicate, under constant salinity and temperature. Mussels were fed every two days, and water renewed every seven days and Ti concentrations re-stabilized. During the first 28 days of experimental period, mussels were exposed to four short pulses of contamination, followed by few days of low Ti concentration between weekly contamination renewals. Then mussels were exposed to additional 14-day exposure to Ti uncontaminated seawater. Only residual Ti concentrations were measured in mussels' whole soft tissue after the four pulses of Ti contamination, indicating low Ti accumulation by the organisms. Nevertheless, the biomarkers related to mussels' metabolic capacity (electron transport system activity, ETS), oxidative damage (lipid peroxidation, LPO and reduced glutathione content, GSH), and defense mechanisms (antioxidant and biotransformation enzymes) evidenced the impact of Ti during the 28 days of experimental period. The biomarkers that better indicated the recovery of mussels' biochemical performance were the ETS, LPO, GSH, and the antioxidant enzyme glutathione peroxidase (GPx). LPO was the prime indicator among the analyzed biochemical responses. Organisms appear to hold coping mechanisms to lower the damage induced by Ti, and to recover, albeit the 14 days period of exposure to uncontaminated seawater following the four Ti pulses were not enough for full recovery, as evidenced by results on LPO levels and GSH concentrations. Despite the low solubility of Ti in seawater, the toxicity of this element to a model marine organism was demonstrated.

Titanium dioxide nanoparticle exposure reduces algal biomass and alters algal assemblage composition in wastewater effluent-dominated stream mesocosms

A 5-week mesocosm experiment was conducted to investigate the toxicity of titanium dioxide nanoparticles (TiO2NPs) to periphytic algae in an environmentally-realistic scenario. We used outdoor experimental streams to simulate the characteristics of central Texas streams receiving large discharges of wastewater treatment plant effluent during prolonged periods of drought. The streams were continually dosed and maintained at two concentrations. The first represents an environmentally relevant concentration of 0.05 mg L−1 (low concentration). The second treatment of 5 mg L−1 (high concentration) was selected to represent a scenario where TiO2NPs are used for photocatalytic degradation of pharmaceuticals in wastewater. Algal cell density, chlorophyll-a, ash-free dry mass, algal assemblage composition, and Ti accumulation were determined for the periphyton in the riffle sections of each stream. The high concentration treatment of TiO2NPs significantly decreased algal cell density, ash-free dry mass, and chlorophyll-a, and altered algal assemblage composition. Decreased abundance of three typically pollution-sensitive taxa and increased abundance of two genera associated with heavy metal sorption and organic pollution significantly contributed to algal assemblage composition changes in response to TiO2NPs. Benefits of the use of TiO2NPs in wastewater treatment plants will need to be carefully weighed against the demonstrated ability of these NPs to cause large changes in periphyton that would likely propagate significant effects throughout the stream ecosystem, even in the absence of direct toxicity to higher trophic level organisms.

Trophic transfer potential of two different crystalline phases of TiO2 NPs from Chlorella sp. to Ceriodaphnia dubia

Owing to the increase in the usage of titanium dioxide nanoparticles (TiO2 NPs), their release into the aquatic environment is inevitable. In the aquatic ecosystem, TiO2 NPs can bio-magnify at various trophic levels in the food chain through dietary exposure. In the current study, the trophic transfer potential of two crystalline phases of TiO2, anatase and rutile nanoparticles (individual as well as a binary mixture) has been evaluated in the lake water matrix using algae–daphnia system. Chlorella sp. and Ceriodaphnia dubia were used as test organisms to represent the algae–daphnia food chain of the freshwater ecosystem. Other than crystallinity, the effect of irradiation (visible and UV-A) was also investigated at the test concentrations, 75, 300, and 1200 μM. TiO2 NPs treated algal diet produced significant mortality only at the test concentrations, 300 and 1200 μM. The type of irradiation and crystallinity doesn’t have any impact on the mortality of daphnids through the dietary exposure of TiO2 NPs. Comparing the mixture with individual NPs, binary mixture induced less mortality on C. dubia which signifies the antagonistic effect of NPs when they coexist. Statistical modeling confirmed the antagonistic effect of the binary mixture on C. dubia. As individual NPs, anatase and rutile forms showed a maximum Ti accumulation under UV-A and visible irradiation, respectively. BMF of TiO2 NPs has been in validation with the bioaccumulation noted in C. dubia. Individual NPs (75 μM) showed higher BMF value of ∼23 under both UV-A (anatase) and visible (rutile) irradiation. Individual NPs showing higher BMF confirmed their trophic transfer potential in the aquatic food chain, primarily through the diet. In contrast, the binary mixture obtained a higher BMF of 1.9 and 0.79 at 75 and 300 μM under visible and UV-A irradiation, respectively. The plausible reason behind this decrement was the antagonistic effect of the mixture which significantly reduced their Ti bioaccumulation on C. dubia.

Multiple Method Analysis of TiO2 Nanoparticle Uptake in Rice (Oryza sativa L.) Plants.

Understanding the translocation of nanoparticles (NPs) into plants is challenging because qualitative and quantitative methods are still being developed and the comparability of results among different methods is unclear. In this study, uptake of titanium dioxide NPs and larger bulk particles (BPs) in rice plant (Oryza sativa L.) tissues was evaluated using three orthogonal techniques: electron microscopy, single-particle inductively coupled plasma mass spectroscopy (spICP-MS) with two different plant digestion approaches, and total elemental analysis using ICP optical emission spectroscopy. In agreement with electron microscopy results, total elemental analysis of plants exposed to TiO2 NPs and BPs at 5 and 50 mg/L concentrations revealed that TiO2 NPs penetrated into the plant root and resulted in Ti accumulation in above ground tissues at a higher level compared to BPs. spICP-MS analyses revealed that the size distributions of internalized particles differed between the NPs and BPs with the NPs showing a distribution with smaller particles. Acid digestion resulted in higher particle numbers and the detection of a broader range of particle sizes than the enzymatic digestion approach, highlighting the need for development of robust plant digestion procedures for NP analysis. Overall, there was agreement among the three techniques regarding NP and BP penetration into rice plant roots and spICP-MS showed its unique contribution to provide size distribution information.

Continuous in vitro exposure of intestinal epithelial cells to E171 food additive causes oxidative stress, inducing oxidation of DNA bases but no endoplasmic reticulum stress

The whitening and opacifying properties of titanium dioxide (TiO2) are commonly exploited when it is used as a food additive (E171). However, the safety of this additive can be questioned as TiO2 nanoparticles (TiO2-NPs) have been classed at potentially toxic. This study aimed to shed some light on the mechanisms behind the potential toxicity of E171 on epithelial intestinal cells, using two in vitro models: (i) a monoculture of differentiated Caco-2 cells and (ii) a coculture of Caco-2 with HT29-MTX mucus-secreting cells. Cells were exposed to E171 and two different types of TiO2-NPs, either acutely (6–48 h) or repeatedly (three times a week for 3 weeks). Our results confirm that E171 damaged these cells, and that the main mechanism of toxicity was oxidation effects. Responses of the two models to E171 were similar, with a moderate, but significant, accumulation of reactive oxygen species, and concomitant downregulation of the expression of the antioxidant enzymes catalase, superoxide dismutase and glutathione reductase. Oxidative damage to DNA was detected in exposed cells, proving that E171 effectively induces oxidative stress; however, no endoplasmic reticulum stress was detected. E171 effects were less intense after acute exposure compared to repeated exposure, which correlated with higher Ti accumulation. The effects were also more intense in cells exposed to E171 than in cells exposed to TiO2-NPs. Taken together, these data show that E171 induces only moderate toxicity in epithelial intestinal cells, via oxidation.

Effects of TiO2 nanoparticles on wheat (Triticum aestivum L.) seedlings cultivated under super-elevated and normal CO2 conditions.

Concerns over the potential risks of nanomaterials to ecosystem have been raised, as it is highly possible that nanomaterials could be released to the environment and result in adverse effects on living organisms. Carbon dioxide (CO2) is one of the main greenhouse gases. The level of CO2 keeps increasing and subsequently causes a series of environmental problems, especially for agricultural crops. In the present study, we investigated the effects of TiO2 NPs on wheat seedlings cultivated under super-elevated CO2 conditions (5000 mg/L CO2) and under normal CO2 conditions (400 mg/L CO2). Compared to the normal CO2 condition, wheat grown under the elevated CO2 condition showed increases of root biomass and large numbers of lateral roots. Under both CO2 cultivation conditions, the abscisic acid (ABA) content in wheat seedlings increased with increasing concentrations of TiO2 NPs. The indolepropioponic acid (IPA) and jasmonic acid (JA) content notably decreased in plants grown under super-elevated CO2 conditions, while the JA content increased with increasing concentrations of TiO2 NPs. Ti accumulation showed a dose-response manner in both wheat shoots and roots as TiO2 NPs concentrations increased. Additionally, the presence of elevated CO2 significantly promoted Ti accumulation and translocation in wheat treated with certain concentrations of TiO2 NPs. This study will be of benefit to the understanding of the joint effects and physiological mechanism of high-CO2 and nanoparticle to terrestrial plants.

Titanium Dioxide Nanoparticles Alleviate Tetracycline Toxicity to Arabidopsis thaliana (L.)

Arabidopsis thaliana (L.) Heynh. was used as a model plant to investigate the biochemical and molecular response upon coexposures to tetracycline (TC) and titanium oxide nanoparticles (TiO2 NPs). Results showed that 1 mg/L TC severely reduced A. thaliana biomass by 33.3% as compared with the control; however, the presence of 50 and 100 mg/L TiO2 NPs alleviated TC toxicity, increasing fresh biomass by 45% and 28%, respectively, relative to the TC alone treatment. The presence of TC notably decreased Ti accumulation in both shoots and roots. Antioxidant enzyme activity, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD), in A. thaliana shoots and roots indicated that TC significantly increased the activity of reactive oxygen species (ROS) scavengers. However, in the coexposure treatments, TiO2 NPs reduced antioxidant enzyme activity back to the control levels. The relative expression of genes encoding sulfur assimilation and glutathione biosynthesis pathwa...