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Background: Non-spherical titanium dioxide (TiO 2 ) nanoparticles have been increasingly applied in various biomedical and technological fields. Their toxicological characterization is, however, less complete than that of roundish nanoparticles., Materials and Methods: Anatase form TiO 2 nanorods, ca. 15x65 nm in size, were applied to cultured astrocytes in vitro and to the airways of young adult Wistar rats in vivo in 5, 10, and 8 mg/kg BW dose for altogether 28 days. Presence of nanorods and cellular damage was investigated in the astrocytes and in rat lungs and kidneys. Functional damage of the nervous system was studied by electrophysiological methods., Results: The treated astrocytes showed loss of viability without detectable apoptosis. In rats, TiO 2 nanorods applied to the airways reached the blood and various organs including the lungs, kidneys, and the central nervous system. In lung and kidney samples, nanorods were observed within (partly damaged) phagolysosomes and attached to organelles, and apoptotic cell death was also detected. In cortical and peripheral electrophysiological activity, alterations corresponding to energy shortage (resulting possibly from mitochondrial damage) and astrocytic dysfunction were detected. Local titanium levels and relative weight of the investigated organs, apoptotic cell death in the lungs and kidneys, and changes in the central and peripheral nervous activity were mostly proportional to the applied doses, and viability loss of the cultured astrocytes was also dose-dependent, suggesting causal relationship of treatments and effects., Conclusion: Based on localization of the visualized nanorods, on neuro-functional changes, and on literature data, the toxic mechanism involved mitochondrial damage, oxidative stress, and apoptotic cell death. These indicate potential human toxicity and occupational risk in case of exposure to rod-shaped TiO 2 nanoparticles., Competing Interests: The authors report no conflicts of interest in this work. This work is partially based on the PhD thesis of Tamara Horváth (Szeged, 2019)., (© 2020 Papp et al.)

Background: Titanium dioxide nanoparticles have numerous applications, resulting in human exposure. Nonetheless, available toxicological and safety data are insufficient regarding aspherical particles, such as rod-shaped nanoparticles., Methods: In a combined in vitro-in vivo approach, cultured A549 lung alveolar adenocarcinoma cells were treated with approximately 15×65 nm TiO 2 nanorod-containing medium, while young adult rats received the same substance by intratracheal instillation for 28 days in 5 and 18 mg/kg body-weight doses. Nanoparticle accumulation in the lungs and consequent oxidative stress, cell damage, and inflammation were assessed by biochemical and histopathological methods., Results: Titanium was detected in tissue samples by single-particle inductively coupled plasma mass spectrometry. Nanoparticles were visualized inside cultured A549 cells, within pulmonary macrophages, and in hilar lymph nodes of the rats. A549 cells showed dose-dependent oxidative stress and lethality, and the observed nanoparticle-laden endosomes suggested deranged lysosomal function and possible autophagy. Strongly elevated Ti levels were measured in the lungs of nanorod-treated rats and moderately elevated levels in the blood of the animals. Numerous cytokines, indicating acute and also chronic inflammation, were identified in the lung samples of TiO 2 -exposed rodents., Conclusion: Several signs of cell and tissue damage were detected in both the cultured alveolar cells and in treated rats' lungs. Rod-shaped nanoparticulate TiO 2 may consequently be more harmful than has generally been supposed. The occupational health risk suggested by the results calls for improved safety measures., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Titanate nanotube (TNT) has recently been explored as a new carrier material for active pharmaceutical ingredients (API). The aim of the present work was to reveal the physicochemical properties of API-TNT composites, focusing on the interactions between the TNTs and the incorporated APIs. Drugs belonging to different Biopharmaceutical Classification System (BCS) classes were loaded into TNTs: diltiazem hydrochloride (BCS I.), diclofenac sodium (BCS II.), atenolol (BCS III.) and hydrochlorothiazide (BCS IV.). Experimental results demonstrated that it is feasible for spiral cross-sectioned titanate nanotubes to carry drugs and maintain their bioactivity. The structural properties of the composites were characterized by a range of analytical techniques, including FT-IR, DSC, TG-MS, etc. The interactions between APIs and TNTs were identified as electrostatic attractions, mainly dominated by hydrogen bonds. Based on the results, it can be stated that the strength of the association depends on the hydrogen donor strength of the API. The drug release of incorporated APIs was evaluated from compressed tablets and compared to that of pure APIs. Differences noticed in the dissolution profiles due to incorporation showed a correlation with the strength of interactions between the APIs and the TNTs observed in the above analytical studies., (Copyright © 2016 Elsevier B.V. All rights reserved.)

One-dimensional titanate nanotubes (TiONTs) were subjected to systematic ion exchange to determine the impact of these modifications on biological activities. Ion exchanged TiONTs (with Ag, Mg, Bi, Sb, Ca, K, Sr, Fe, and Cu ions) were successfully synthesized and the presence of the substituted ions was verified by energy dispersive X-ray spectroscopy (EDS). A complex screening was carried out to reveal differences in toxicity to human cells, as well as in antibacterial, antifungal, and antiviral activities between the various modified nanotubes. Our results demonstrated that Ag ion exchanged TiONTs exerted potent antibacterial and antifungal effects against all examined microbial species but were ineffective on viruses. Surprisingly, the antibacterial activity of Cu/TiONTs was restricted to Micrococcus luteus. Most ion exchanged TiONTs did not show antimicrobial activity against the tested bacterial and fungal species. Incorporation of various ions into nanotube architectures lead to mild, moderate, or even to a massive loss of human cell viability; therefore, this type of biological effect exerted by TiONTs can be greatly modulated by ion exchange. These findings further emphasize the contribution of ion exchange in determining not only the physical and chemical characteristics but also the bioactivity of TiONT against different types of living cells., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Titanate nanotubes can be used as drug delivery systems, but limited information is available on their interactions with intestinal cells. In this study, we investigated the cytotoxicity and cellular uptake of titanate nanotubes on Caco-2 monolayers and found that up to 5 mg/ml concentration, these nanotubes are not cytotoxic and not able to permeate through the intestinal cell layer. Transmission electron microscopic experiments showed that titanate nanotubes are not taken up by cells, only caused a high-density granulation on the surface of the endoplasmic reticulum. According to these results, titanate nanotubes are suitable systems for intestinal drug delivery.

Titanate nanotubes (TNTs) are promising vectors for drug delivery due to their unique physicochemical properties such as biocompatibility, mechanical strength, and chemical resistivity. However, considering their strong hydrophilicity, pristine TNTs exert very limited permeability through the intestinal cell layer. The aim of this study was to turn the surface characteristics and thus enhance the permeability of TNTs by functionalization. TNTs were functionalized with trichloro(octyl)silane (TCOS) and magnesium stearate (MgSt). Carbon content and surface free energy of the functionalized TNTs were detected to evaluate the effectiveness of functionalization, by using CHNS analytical and optical contact angle (OCA) measurements, respectively. Caco-2 cell line was applied to test the permeability and the cytotoxicity of the samples. Cytotoxicity was evaluated by using MTT assay. The results revealed that the surface characteristics of TNTs may be adjusted in a wider range with TCOS-TNT than with St, but the samples show higher toxicity. Silane functionalized TNTs may be safe up to 1 mg/ml, while St functionalized TNTs up to 2 mg/ml concentration. The preparation method of MgSt-TNT was also superior from the aspect of environmental safety. The permeability was suitable for samples with moderate hydrophobicity (aqueous contact angle 60-90°). [ABSTRACT FROM AUTHOR]

Titanate nanotubes offer certain benefits like high specific surface area, anisotropic mesoporous structure and ease of synthesis over other nanostructured titania forms. However, their application in visible light driven photocatalysis is hindered by their wide band-gap, which can be remedied by, e.g., anionic doping. Here we report on a systematic study to insert nitrogen into lattice positions in titanate nanotubes. The efficiency of N2+ bombardment, N2 plasma and NH3 plasma treatment is compared to that of NH3 gas synthesized in situ by the thermal decomposition of urea or NH4F. N2+ bombarded single crystalline rutile TiO2 was used as a doping benchmark (16 at.% N incorporated). Surface species were identified by diffuse reflectance infrared spectroscopy, structural features were characterized by scanning electron microscopy and powder X-ray diffraction measurements. The local chemical environment of nitrogen built into the nanotube samples was probed by X-ray photoelectron spectroscopy. Positively charged NH3 plasma treatment offered the best doping performance. This process succeeded in inserting 20 at.% N into nanotube lattice positions by replacing oxygen and forming Ti-N bonds. Remarkably, the nanotubular morphology and titanate crystal structure were both fully conserved during the process. Since plasma treatment is a readily scalable technology, the suggested method could be utilized in developing efficient visible light driven photocatalysts based on N-doped titanate nanotubes. [ABSTRACT FROM AUTHOR]

Graphene-like nanostructures were synthesized from multiwall carbon nanotubes through chemical exfoliation route in mild conditions. For this purpose multiwall carbon nanotubes were synthesized by Chemical Vapor Deposition method using Al-Fe-Co catalyst and treated with KMnO4. The obtained nanostructures were characterized by Raman spectroscopy, XRD, FTIR, EDX, SEM and TEM methods. FTIR results show that, treating the carbon nanotubes with KMnO4decorates their surface with oxygen containing functional groups. XRD and Raman spectroscopy results reveal that the outermost layers of the nanotubes were exfoliated during the treatment. The formation of graphene-like nanostructures was confirmed by SEM and TEM methods. The novelty of this work is the first time use of this type of mild and cheap condition for obtaining graphene-like nanostructures from MWCNTs without any other intermediate treatment. [ABSTRACT FROM PUBLISHER]

Abstract: Multiwall carbon nanotubes were synthesized using the catalytic chemical vapor deposition (CVD) technique followed by an oxidative purification process. The nanotube modified by functional groups were connected by pre-synthesized oligonucleotides in solution. The material thus obtained was characterized by various microscopic methods. The preparation of nanotube chips is discussed. [Copyright &y& Elsevier]

Abstract: Synthesis of carbon nanotubes (CNTs) from the template molecules of the Si-MCM-41 and Al,Si-MCM-41 mesoporous silicates were investigated. The generation of nanotubes was carried out by graphitization, i.e. applying high temperature treatment of the MCM-41 samples in inert gas atmosphere. The as-synthesized and graphitized samples were characterized by several spectroscopic and physico-chemical methods such as IR and MAS NMR spectroscopy, XRD, TEM, and BET. [Copyright &y& Elsevier]

The present text describes an investigation of XPS study of multiwall carbon nanotube (MWNT) synthesis. The aim of the investigation was not only to improve the reaction activity by mixing nickel with vanadium, but also to understand the formation mechanism of the nanotubes. Carbon nanotubes were produced by catalytic chemical vapor deposition (CCVD) of acetylene on transition metal containing catalysts supported on zeolite ZSM-5. The samples were characterized at two different levels. At the nanoscale, they were studied by transmission electron microscopy (TEM), while at macroscopic scale mainly XPS was used to investigate the changes during the reaction. [Copyright &y& Elsevier]

The present work aims to reveal the pharma-industrial benefits of the use of hydrothermally synthesised titanate nanotube (TNT) carriers in the manufacturing of nano-sized active pharmaceutical ingredients (APIs). Based on this purpose, the compressibility and compactibility of various APIs (diltiazem hydrochloride, diclofenac sodium, atenolol and hydrochlorothiazide) and their 1:1 composites formed with TNTs were investigated in a comparative study, using a Lloyd 6000R uniaxial press instrumented with a force gauge and a linear variable differential transformer extensometer. The tablet compression was performed without the use of any excipients, thus providing the precise energetic characterisation of the materials' behaviour under pressure. In addition to the powder functionality test, the post-compressional properties of the tablets were also determined and evaluated. The results of the energetic analysis demonstrated that the use of TNTs as drug carriers is beneficial in every step of the tabletting process: besides providing better flowability and more favourable particle rearrangement, it highly decreases the elastic recovery of the APIs and results in ideal plastic deformation. Moreover, the post-compressional properties of the TNT–API composites were found to be exceptional (e.g., great tablet hardness and tensile strength), affirming the above results and proving the potential in the use of TNT carriers for drug manufacturing. [ABSTRACT FROM AUTHOR]

Abstract: Trititanate nanotubes were prepared from anatase TiO2 in 10M Na2S solution kept at 130°C for 2 weeks. On the basis of this reaction, we devised a novel synthesis method which allows the preparation of titanate nanotubes decorated with CdS nanoparticles in one step. The key feature of the suggested method is controlling the rate of CdS formation by introducing Cd2+ ions as a Cd–EDTA complex into the synthesis mixture. The nanotubes obtained are several hundred nm long, tend to aggregate into rod-like structures and are fully covered by CdS nanoparticles with an average diameter of ∼5.3nm. [Copyright &y& Elsevier]

Abstract: Mesoporous MCM-41-carbon nanocomposites were prepared in several Si:C ratios from amorphous active carbon, graphite and multi-wall carbon nanotube carbon sources. A complete morphological characterization of the samples was performed using XRD, TEM, SEM, N2 adsorption and surface hydrophilicity measurements. Specific surface area, pore size distribution, surface fractal dimension and the dimension of capillary condensation were calculated and the adsorption excess isotherms of the ethanol–cyclohexane system were measured. Our results show that the three carbon types give rise to rather different composite morphological features. On this basis the fine tuning of carbon–silicate composite properties by design appears feasible. [Copyright &y& Elsevier]

Abstract: A systematic study on the morphological changes experienced by multi-wall carbon nanotubes during long-time ball milling in a vibrating mill was performed. Samples were collected in the time interval 0–200h and analyzed with TEM and N2 adsorption. The change of the mean nanotube length with time could be approximated with a second-order exponential decay function. The length distribution function changed from the original log-normal to normal after 140h of milling. Specific surface area, surface fractal dimension, the dimension of the capillary condensation and the pore size distribution (PSD) curve were calculated from the N2 adsorption isotherms. These morphological descriptors all experienced characteristic changes after ∼40h of milling: the specific surface area decreased, the fractal dimension increased and the maximum of the PSD curve shifted downwards by ∼0.5nm. Results indicate that ball milling of carbon nanotubes is a rather complex process and that it can cause several morphological changes to samples besides the well-known cutting effect. [Copyright &y& Elsevier]

Multiwall carbon nanotubes (MWNTs) were synthesized by a novel method of mesoporous MCM-41 and MCM-48 silicates in the absence of any metal traces. A transmission electron microscopy (TEM) study shows that the diameter distribution of the obtained carbon nanotubes is very narrow – 5–6 nm in diameter and 200 nm in length – compared to nanotube samples produced by other catalytic chemical vapor deposition (CCVD) techniques. [Copyright &y& Elsevier]

The photocatalytic transformation of the methane-carbon dioxide system was investigated by in-situ methods in the present study. Titanate nanotube (TNT) supported gold and rhodium catalysts were used in the catalytic tests. Our main goal was the analysis of the role of the catalysts in the different parts of the reaction mechanism. The catalysts were characterized by X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and diffuse reflectance UV–vis spectroscopy (DR-UV–vis). Photocatalytic tests were performed in a continuous flow quartz reactor equipped with mass spectrometer detector and mercury-arc UV source. Diffuse reflectance infrared spectroscopy (DRIFTS) was used to analyze the surface of the catalyst during photoreaction. Post-catalytic tests were also carried out on the catalysts including XPS, temperature programmed reduction (TPR) and Raman spectroscopy methods in order to follow the changes of the materials. Titanate nanotube can stabilize even the smallest, molecular-like Au clusters which showed the highest activity in the reactions. Approximately 3% methane conversion was reached in the best cases while the carbon dioxide conversion was not traceable. It was revealed that water has a very important role in the oxidation reaction. The main discovered reaction routes are methane dehydrogenation and oxidation, the methyl coupling and the forming of structured carbon deposits on the catalyst surface. The source of the surplus CO can be mostly the reduction of carbon dioxide. During the reduction process photoelectrons and hydrogen ions brings about the CO 2 reduction via CO 2 − radical anion. [ABSTRACT FROM AUTHOR]

Highlights: [•] Titanate nanotubes were utilized in Ca2+ and Mg2+ removal in an ion-exchange unit. [•] The highest measured value of the total ion-exchange capacity was 1.2mmolg−1. [•] The ion-exchange capacity decreased to 0.66mmolg−1 in the third cycle. [•] Capacity loss was due to irreversible binding of Ca2+ to strong adsorption sites. [•] The Mg2+/Na+ exchange was reversible. [ABSTRACT FROM AUTHOR]

Abstract: 90–100nm long protonated titanate nanotubes were synthesized by hydrothermal method from anatase at 155°C. The bismuth and antimony affected crystallization of the tubular titanate structures during calcination was studied by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. It was shown that bismuth and antimony have different effects on the transformation; while in the presence of antimony oxide the trititanate–anatase–rutile phase transformation is hindered, the bismuth oxide promotes the crystallization process to rutile. [Copyright &y& Elsevier]

Abstract: This study explores the possibility of converting a self-supporting, randomly aligned, low impedance multi-wall carbon nanotube (MWCNT) paper into a resistive temperature measurement unit working at ambient pressure in air in the 25–70°C range. Thermosensitization was achieved by decorating the surface of the films with pyroelectric CsNO3 or LiNbO3 crystals. Assuming a linear temperature response, temperature coefficient of resistance values of −0.158%°C−1 and −0.246%°C−1 were calculated for CsNO3 and LiNbO3 doped films, respectively. The corresponding temperature measurement accuracies (2.2°C and 3.0°C) are acceptable for some applications but the precision of the temperature measurement needs to be improved. [Copyright &y& Elsevier]

Abstract: Silicon nitride based composites with different amount (1, 3 or 5wt%) of carbon nanotubes have been prepared by using hot isostatic pressing. Composites with 1, 5 or 10wt% carbon black and graphite have been manufactured, in comparison. Optimisation of the manufacturing processes has been performed, providing intact carbon nanotubes during high temperature sintering. In the case of 1 or 3 wt% carbon nanotube addition, the increase of gas pressure during sintering resulted in an increase of bending strength. It was found that microstructure features achieved by properly designed sintering parameters are the main responsible factors for the strength improvements. Scanning electron microscopy showed that carbon nanotubes have a good contact to the surface of silicon nitride grains. The electrical properties of silicon nitride matrices with carbon addition may change essentially. [Copyright &y& Elsevier]

Abstract: Ion-exchangable titanate nanotubes synthesized by the alkali treatment of TiO2 (anatase) were rendered photochemically active by decorating them with CdS nanoparticles through a simple wet chemical process. HRTEM, Raman and IR observations suggest that the activation could be caused by the strong coupling between the nanotube and the nanoparticles. [Copyright &y& Elsevier]

Catalytically prepared multiwall carbon nanotubes (MWNTs) were cut and functionalised by mechanical and/or chemical methods. Products were characterised by transmission electron microscopy, infrared spectroscopy and BET method. It can be concluded that physical and chemical breaking procedures complete each other very well. With certain MWNT samples containing surface oxides preliminary investigations were done for testing them as catalyst support. [Copyright &y& Elsevier]