Impact of titanium dioxide nanoparticles on the bacterial communities of biological activated carbon filter intended for drinking water treatment

ZnO-NPs/AC composite antibacterial agents with N-halamine glycinate functionalized silica-mesoporous silica coating for water disinfection

This work deals with the synthesis, structural characterization and applications of N-halamine glycinate functionalized silica-mesoporous silica coated ZnO-NPs/AC composite for water disinfection. Several nanocomposite materials were obtained: ZnO-NPs/AC, ZnO-NPs/AC@SiO2, ZnO-NPs/AC@SiO2@mSiO2, ZnO-NPs@SiO2@mSiO2-Gly and ZnO-NPs@SiO2@mSiO2-N-halamine-Gly. These nanocomposite materials were fully characterized via different physiochemical techniques including: FTIR, TGA, XPS, XRD, SEM, TEM and BET. XRD indicated a predominance of crystalline pattern of ZnO-NPs impregnated into activated carbon (AC) and their silica and m-mesoporous silica coating precursors. The FTIR spectra confirmed an immense combination between ZnO-NPs and AC of ZnO-NPs/AC nanocomposite as well as its interactions with coated silica precursors. SEM, TEM images illustrated that the fabricated ZnO-NPs/AC nanocomposites are well coated with silica-mesoporous silica functionalized N-halamine. The distinctive surface area has decreased from 800 m2/g for pristine AC to 772 m2/g for ZnO-NPs/AC and to 282 m2/g for ZnO-NPs/AC@SiO2 and to 139 m2/g for ZnO-NPs/AC@SiO2@mSiO2 and to 15.4 m2/g for ZnO-NPs@SiO2@mSiO2-N-Gly. All those nanocomposites showed good efficacy against all four bacterial species, with higher inhibition zones for the 2 g-positive bacteria than that of the 2 g-negative ones. The ZnO@SiO2@mSiO2-N-halamine-Gly exhibited the high zone inhibition against all tested bacteria except for E. Coli.

Impact of titanium dioxide nanoparticles on intestinal community in 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced acute colitis mice and the intervention effect of vitamin E

Titanium dioxide nanoparticles (TiO2-NPs) are widely applied as additives in foods due to their excellent whitening and brightening capability. Although the toxicity and antibacterial activity of TiO2-NPs have been extensively studied, their impact on the gut microbiota in vivo still remains unclear, especially in animals with gastrointestinal disorders. In the present study, healthy mice and TNBS-induced colitis mice were administered with TiO2-NPs (38.3 ± 9.3 nm) orally at a dose of 100 mg per kg bw daily for 10 days to study the impact of TiO2-NPs on the gut microbiota and colitis development. Moreover, the mechanism of TiO2-NPs on the gut microbiota was also discussed when the colitis mice were additionally administered with vitamin E to remove ROS. Changes in the microbiota community structure and gut-associated function prediction were analyzed through bioinformatics. The result showed that the oral administration of TiO2-NPs mitigated colitis symptoms by reducing the DAI and CMDI scores and TNF-α level. Furthermore, 16S rDNA sequencing analysis showed that the structure and function prediction of gut microbiota could be modified in healthy mice and colitis mice after exposure to TiO2-NPs, but the opposite physiological effect occurred since the dominant flora varied in these two groups. Moreover, vitamin E intervention did not change the effects of TiO2-NPs on the microbiota community structure and gut-associated function, which indicates that the mechanism of the biological effects of TiO2-NPs on the gut microbiota may not be associated with their ability to induce the generation of ROS. In summary, our work firstly found that TiO2-NPs could regulate the gut microbiota of colitis mice and participate in the mitigation of TNBS-induced acute colitis, and the capability of TiO2-NPs to induce the generation of ROS inducement did not contribute to this process.

Novel biologically active polyurea derivatives and its TiO2-doped nanocomposites

A new series of polyurea derivatives and its nanocomposites were synthesised by the solution polycondensation method through the interaction between 4(2-aminothiazol-4-ylbenzylidene)-4-(tert-butyl) cyclohexanone and diisocyanate compound in pyridine. The PU1-3 structure was confirmed using Fourier transform-infrared (FTIR) spectroscopy and characterised by solubility, viscometry, gel permeation chromatography (GPC), and X-ray diffraction (XRD) analysis. In addition, PU1-3 was evaluated by TGA. Polyurea-TiO2nanocomposites were synthesised using the same technique as that of PU1-3 by adding TiO2 as a nanofiller. The thermal properties of PU2TiO2a-d were evaluated by TGA. Moreover, the morphological properties of a selected sample were examined by SEM and TEM. In addition, PU1-3 and PU2TiO2a-d were examined for antimicrobial activity against certain bacteria and fungi. The PU1-3 showed antibacterial activity against some of the tested bacteria and fungi, as did PU2TiO2a-d, which increased with the increase in TiO2 content. Furthermore, molecular docking studies were displayed against all PU1-3 derivatives against two types of proteins. The results show that the increase in the strength of π-H interactions and H-donors contributed to improved binding of PU2 compared to PU1 andPU3. The docking of 1KZN against the tested polymers suggests an increase in the docking score of PU2, then PU1, and PU3, which is in agreement with the antibacterial study.

Impact of the production method and diagnostics conditions on the compositions and structure of nanodimensional anatase

The detail investigation of the samples with nanodimensional anatase, formed by hydrolysis of TiOSO4 × xH2O without or in the presence of polymer poly(N-vinyl caprolactam), physical precipitation of the polymer followed by the capture of commercial Hombifine N are performed by X-ray powder diffraction using laboratory and synchrotron radiation sources, transmission electron microscopy with the diffraction, and elemental analysis. The two «core»-«shell» models with nanoparticles and their associates as a core can be applied to samples produced. The synchrotron and electron radiation change the degree of crystallinity and the imperfection of anatase, isolate of TiO2−x(OH)2x × yH2O from the nanoparticle shell with a decrease in its thickness, lead to the anatase – rutile phase transition. The double diffraction effect on the appearance of kinematically forbidden reflections caused by the dynamic character of the electron diffraction. The photoactivity depends on microstructural characteristics (specific surface, nanoobjects sizes). The structure and elemental composition of nanoparticles (associates) affect antimicrobial activity against Staphylococcus aureus and Escherichia coli.

Carbon nanomaterials alter plant physiology and soil bacterial community composition in a rice-soil-bacterial ecosystem

The aim of this study was to compare the toxicity effects of carbon nanomaterials (CNMs), namely fullerene (C₆₀), reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs), on a mini-ecosystem of rice grown in a loamy potted soil. We measured plant physiological and biochemical parameters and examined bacterial community composition in the CNMs-treated plant-soil system. After 30 days of exposure, all the three CNMs negatively affected the shoot height and root length of rice, significantly decreased root cortical cells diameter and resulted in shrinkage and deformation of cells, regardless of exposure doses (50 or 500 mg/kg). Additionally, at the high exposure dose of CNM, the concentrations of four phytohormones, including auxin, indoleacetic acid, brassinosteroid and gibberellin acid 4 in rice roots significantly increased as compared to the control. At the high exposure dose of MWCNTs and C₆₀, activities of the antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD) in roots increased significantly. High-throughput sequencing showed that three typical CNMs had little effect on shifting the predominant soil bacterial species, but the presence of CNMs significantly altered the composition of the bacterial community. Our results indicate that different CNMs indeed resulted in environmental toxicity to rice and soil bacterial community in the rhizosphere and suggest that CNMs themselves and their incorporated products should be reasonably used to control their release/discharge into the environment to prevent their toxic effects on living organisms and the potential risks to food safety.