Toxicity of a Binary Mixture of TiO2 and Imidacloprid Applied to Chlorella vulgaris

Combined effects of TiO2 nanoparticle and fipronil co-exposure on microbiota in mouse intestine

Oral exposure to nanoparticles (NPs) may affect intestinal microbiota, and this effect may be further changed by co-contaminates. In the present study, we investigated the combined effects of TiO2 NPs and fipronil (FPN) on microbiota in mouse intestines. Mice were intragastric exposed to 5.74 mg/kg TiO2 NPs, 2.5 mg/kg FPN, or both of them, once a day, for 30 days. The results showed that individual exposure to TiO2 NPs or FPN decreased body weight and induced pathological changes in intestines. The exposure was also associated with increased cleaved caspase-3 protein, oxidative stress and decreased tight junction protein expression. Furthermore, the levels of diamine oxidase (DAO), lipopolysaccharide (LPS) and inflammatory cytokines in serum were also elevated, indicating increased intestinal barrier permeability. As expected, both TiO2 NPs and FPN decreased the diversity and altered the composition of microbiota. However, the observed effects were not further enhanced after the co-exposure to TiO2 NPs and FPN, except that Romboutsia was only significantly increased after the co-exposure to TiO2 NPs + FPN. We concluded that oral exposure to TiO2 NPs and FPN showed minimal synergistic effects on microbiota in mouse intestine.

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 (8 weeks) were orally exposed to 5.74 mg/kg TiO2 NPs, 2.5 mg/kg fipronil, or both, once a day, for 5 days. 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.

The combined toxicity of silver nanoparticles and typical personal care products in diatom Navicula sp

Toxicity of silver nanoparticles (AgNPs) at environmentally relevant concentrations has been received an increasing attention, and their influence on the bioavailability of personal care products has been seldom studied. Here, the toxicity of AgNPs in typical diatom Navicula sp. was explored, and their influence on the bioavailability of typical personal care products such as triclosan (TCS) and galaxolide (HHCB) was also investigated. The underlying toxicity mechanisms were explored using liquid chromatography-mass spectrometry (LC-MS)-based metabolomics. Low concentrations of AgNPs (10 and 50 μg L-1) induced no observable responses of Navicula sp., in terms of growth rate, chlorophyll contents, and malondialdehyde accumulation. Furthermore, low doses of AgNPs could attenuate TCS or HHCB toxicity to Navicula sp., which was mainly attributed to the reduced oxidative stress. Metabolomics revealed that the disruption of DNA or RNA synthesis and instability of cytokinin-like substances may be also the reasons for the toxicity of AgNPs and TCS to Navicula sp. The damaged algal photosynthesis exposed to HHCB may be recovered by AgNPs, and the presence of signal chemicals (dehydrophytosphingosine and cardamonin) also showed a recovered algal growth. These results emphasize the potential of metabolomics to reveal toxicity mechanism, providing a new perspective on the aquatic risk assessment of nanoparticles and emerging organic pollutants.

Cerium oxide thin films: synthesis, characterization, photocatalytic activity and influence on microbial growth

The resistance of surfaces to biofouling remains a significant advantage for optical devices working in natural conditions, increasing their lifetime and reducing maintenance costs. This paper reports on the functionalities of transparent CeO₂ thin films with thicknesses between 25 and 600 nm deposited by reactive magnetron sputtering on the glass substrate. The CeO₂ photocatalytic performance exhibited an efficiency of 30% on imidacloprid degradation under 6 h of UV radiation and increased linearly with the irradiation time, suggesting a complete degradation within 48 h. The films did not alter the growth rate of the green algae Chlorella vulgaris after 72 h short-term exposure. The tested CeO₂ films proved to efficiently inhibit with high efficiency the Staphylococcus aureus biofilms and planktonic growth (reducing the counts of bacterial cells by 2 to 8 logs), demonstrating the promising potential of these materials for obtaining antimicrobial and antibiofilm surfaces, with broad applications for the biomedical, ecological and industrial fields.

Exploring engineering reduced graphene oxide-titanium dioxide (RGO-TiO2) nanoparticles treatment to effectively enhance lutein biosynthesis with Chlorella sorokiniana F31 under different light intensity

The Chlorella sorokiniana F31 is a promising lutein producer with high lutein content. Herein, different graphene/TiO₂ nanoparticles (NPs) were designed and synthesized by hydrothermal method. Through the UV-vis diffuse reflectance spectra (DRS) analysis, the results showed that RGO-TiO₂ NPs can effectively expand visible light absorption compared with TiO₂ NPs. Subsequently, the effects of these NPs on light utilization and lutein accumulation of C. sorokiniana F31 were investigated, and the RGO-TiO₂ NPs treatment exhibited the higher lutein production and content than that of TiO₂ and control group. As the optimal RGO-TiO₂ (0.5 wt%) NPs concentration of 50 mg/L and light intensity of 211 μmol/m²/s, the supreme lutein content (15.55 mg/g), production (77.2 mg/L) and productivity (12.87 mg/L/d) were achieved. The performances are higher than most of reported values in previous study, indicated that RGO-TiO₂ (0.5 wt%) NPs treatment is a promised strategy to enhance microalgal growth and lutein accumulation.

Synthesis, Characterisation, Photocatalytic Activity, and Aquatic Toxicity Evaluation of TiO2 Nanoparticles

Imidacloprid (IMD) is a toxic pesticide, and is one of the eight most widely used pesticides globally. Heterogeneous photocatalysis has often been investigated in recent years and can be successfully applied to remove imidacloprid from water. However, less investigated is the toxic effect of both the photocatalyst and the pesticide on aquatic life. Titanium dioxide (TiO₂) remains the most effective photocatalyst, provided it is not toxic to the aquatic environment. This study investigated the TiO₂ synthesis, characterisation, and photocatalytic activity on imidacloprid degradation and the toxicity of TiO₂ nanoparticles and imidacloprid on the green algae Chlorella vulgaris. In the photodegradation process of IMD (initial concentration of 20 mg/L), electrons play an essential role; the degradation efficiency of IMD after 6 h increased from 69 to 90% under UV irradiation when holes (h⁺) scavengers were added, which allowed the electrons to react with the pollutant, resulting in lowering the recombination rate of electron-hole charge carriers. Growth inhibition of Chlorella vulgaris and effective concentration (EC50) were determined to study the toxic effect of TiO₂ nanoparticles and imidacloprid. The EC50 increased from 289.338 mg/L in the first 24 h to 1126.75 mg/L after 96 h Chlorella vulgaris algal age, when the toxicant was TiO₂. When IMD was the aquatic toxicant, a decrease in EC50 was observed from 22.8 mg/L (24 h) to 0.00777 mg/L (120 h), suggesting a long-term high toxicity level when pesticides in low concentrations are present in an aquatic environment.