Treatment Of Multi-walled Carbon Nanotubes Research Articles

In vitro physiological and biochemical response of Stevia rebaudiana exposure to carbon nanotubes: Hormetic and photomixotrophic effect

Multi-walled carbon nanotubes (MWCNTs) are cylindrical rolled sheets with different applications in plant biotechnology due to their physicochemical characteristics. This study aimed to evaluate the in vitro physiological and biochemical responses of stevia (Stevia rebaudiana Bertoni) exposure to different concentrations of MWCNTs during multiplication phase in liquid medium using temporary immersion bioreactors. The MWCNTs were characterized regarding their properties by transmission electron microscope. Different treatments (0, 25, 50 and 100 mg/L) of MWCNTs were added to Murashige and Skoog semisolid culture medium at the proliferation phase. At 30 d of in vitro multiplication, the number of shoots, shoot length, number of leaves, dry matter, and antioxidant capacity were evaluated, as well as total chlorophyll, carotenoid, macro and micronutrient, phenolic, Phosphoenolpyruvate (PEP) and Rubisco contents. The results showed that adding MWCNTs at low doses (25 and 50 mg/L MWCNT) led to an increase in the in vitro multiplication rate and a higher number of leaves, while, at the highest dose (100 mg/L MWCNT), there was an inhibition of these variables. MWCNT treatments had an effect on Mg, Fe and C elements. The accumulation of photosynthetic pigments was associated with a higher PEP content in MWCNT treatments. Phenolic content increased at a concentration of 100 mg/L MWCNT, while antioxidant capacity increased at a concentration of 50 mg/L MWCNT. In conclusion, the usage of low MWCNT doses could be used to induce a hormetic response and to promote photosynthesis during in vitro propagation of stevia.

Effects of multi-walled carbon nanotubes on gene and microRNA expression in human hepatocarcinoma HepG2 cells.

The usage of multi-walled carbon nanotubes (MWCNT) has increased exponentially in the past years, but, potential toxicity mechanisms are not clear. We studied the transcriptomic alterations induced by one multi-walled carbon nanotube (MWCNT) and its -OH and -COOH functionalized derivatives in human HepG2 cells. We showed that all three MWCNT treatments induced alterations in stress-related signaling pathways, inflammation-related signaling pathways, cholesterol synthesis pathways, proliferation-related pathways, senescence-related pathways and cancer-related pathways. In stress-related pathways, the acute phase response was induced in all three MWCNTs and all doses treated and ranked high. Other stress-related pathways were also related to the oxidative-induced signaling pathways, such as NRF-2 mediated oxidative stress response, hepatic fibrosis/Stella cell activation, iNOS signaling, and Hif1α signaling. Many inflammation-related pathways were altered, such as IL-8, IL-6, TNFR1, TNFR2, and NF-κB signaling pathways. These results were consistent with our previous results with exposures to the same three multi-walled carbon nanotubes in human lung BEAS-2B and also with results in mice and rats. From the microRNA target filter analysis, TXNIP & miR-128-3p interaction was present in all three MWCNT treatments, and maybe important for the induction of oxidative stress. CXCL-8 & miR-146-5p and Wee1 & miR-128-3p were only present in the cells treated with the parent and the OH-functionalized MWCNTs. These mRNA-miRNA interactions were involved in oxidative stress, inflammation, cell cycle, cholesterol biosynthesis and cancer related pathways. Target filter analysis also showed altered liver hyperplasia/hyperproliferation and hepatic cancer pathways. In short, target filter analysis complemented the transcriptomic analysis and pointed to specific gene/microRNA interactions that can help inform mechanism of action. Moreover, our study showed that the signaling pathways altered in HepG2 cells correlated well with the toxicity and carcinogenicity observed in vivo, indicating that HepG2 may be a good in vitro predictive model for MWCNT toxicity studies.

MWCNTs Alleviated saline-alkali stress by optimizing photosynthesis and sucrose metabolism in rice seedling

ABSTRACTSaline and alkali stress affects the growth and development, survival rate, and final yield of rice, while new nano materials can have a positive effect on rice growth. In order to investing the effects of carboxymethyl multi walled carbon nanotubes (MWCNTs) on the growth and development of rice seedlings under salt alkali stress, rice seedlings were cultured using rice variety “Songjing 3” using nutrient solution water culture method. The effects of MWCNTs on water absorption capacity, leaf photosynthesis, and sucrose metabolism of rice seedlings under 50 mmol/L saline-alkali stress (1NaCl: 9Na2SO4: 9NaHCO3: 1Na2CO3) conditions were investigated. The results showed that MWCNTs can improve the water use ability of roots and leaves, especially the water absorption ability of roots, which provides a guarantee for the improvement of rice biomass and the enhancement of leaf photosynthetic capacity under adverse conditions. After treatment with MWCNTs, the photosynthetic rate (Pn), stomatal conductance (gs), and transpiration rate (Tr) of leaves increased significantly, and the photochemical quenching value (qP), photochemical quantum efficiency value (Fv/Fm), and electron transfer rate value (ETR) of chlorophyll fluorescence parameters increased significantly, which is beneficial to the improvement of the PSII photosynthetic system. MWCNTs treatment promoted the increase of photosynthetic pigment content in leaves under salt and alkali stress, improved the ratio of Chla and Chlb parameters, increased the activities of key photosynthetic enzymes (RUBPCase and PEPCase) in leaves, increased the value of total lutein cycle pool (VAZ), and significantly enhanced the deepoxidation effect of lutein cycle (DEPS), which can effectively alleviate the stomatal and non stomatal constraints on leaf photosynthesis caused by salt and alkali stress. MWCNTs treatment significantly enhanced the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SS) under salt and alkali stress, and decreased the activities of soluble acid invertase (SAInv) and alkaline/neutral invertase (A/N-Inv), indicating that MWCNTs promoted sucrose synthesis while inhibiting sucrose decomposition, thereby promoting sucrose accumulation in rice leaves. This study can provide theoretical and experimental basis for the application of MWCNTs to the production of rice under salt and alkali stress, and can find a new way for rice production in saline and alkaline lands.

Treatment of Multi-Walled Carbon Nanotubes with Dichromic Acid: Oxidation and Appearance of Intercalation.

This work is dedicated to the study of the treatment of multi-walled carbon nanotubes (MWCNTs) with dichromic acid. The dichromic acid was formed by dissolving different concentrations of CrO3 in water. The effect of the concentration of dichromic acid on the change in texture characteristics, elemental composition, defectiveness, graphitization degree, and surface chemistry of MWCNTs was investigated using various analytical techniques, such as transmission electron microscopy, energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). Testing of MWCNTs as electrodes for supercapacitors in 3.5 M H2SO4 solution was carried out using cyclic voltammetry. A decrease in the average diameter of CNTs after treatment was found. The EDX and XPS showed that the oxygen content on the surface of MWCNTs increased after treatment with dichromic acid. The formation of Cr2O3 after treatment with dichromic acid was detected by XPS. High angle annular dark field scanning transmission electron microscopy was used to confirm the intercalation of the chromium-containing compound between graphene layers of MWCNTs after treatment with dichromic acid. It was found that two different types of MWCNTs showed diverse behavior after treatment. The highest specific capacitance of the MWCNTs after treatment was 141 F g-1 (at 2 mV s-1) compared to 0.3 F g-1 for the untreated sample.

Unraveling the role of multi-walled carbon nanotubes in a corn-soil system: Plant growth, oxidative stress and heavy metal(loid)s behavior

In the age of nanotechnological advancement, carbon nanotubes (CNTs) are drawing global attention. However, few studies have been published on the crop growth responses to CNTs in heavy metal(loid)s contaminated environments. A pot experiment was conducted to assess the effect of multi-walled carbon nanotubes (MWCNTs) on plant development, oxidative stress, and heavy metal(loid)s behavior in a corn-soil system. Corn (Zea mays L.) seedlings were cultivated in soil containing Cadmium (Cd) and Arsenic (As) that had been primed with 0, 100, 500, and 1000 mg kg−1 MWCNTs. The application of 100 and 500 mg kg−1 MWCNTs improved shoot length by 6.45% and 9.21% after 45 days, respectively. Total plant dry biomass increased by 14.71% when treated with 500 mg kg−1 MWCNTs but decreased by 9.26% when exposed to 1000 mg kg−1 MWCNTs. MWCNTs treatment did not affect Cd accumulation in plants. On the other hand, the bio-concentration factor of As was inversely associated with plant growth (p < 0.05), which was declined in MWCNTs treatments. Oxidative stress was aggravated when plants were exposed to MWCNTs, thus activating the antioxidant enzymes system in the corn. In contrast, TCLP-extractable Cd and As in soil significantly decreased than in the control. Additionally, the soil nutrients were changed under MWCNTs treatments. Our findings also revealed that a particular concentration of MWCNTs can mitigate the toxicity of Cd and As in corn seedlings. Therefore, these results suggest the prospective application of CNTs in agricultural production, ensuring environmental and soil sustainability.

Impacts of ZnO and multi-walled carbon nanotubes (MWCNTs) on biological parameters of the Oriental river prawn Macrobrachium nipponense De Haan, 1849 (Decapoda: Caridea: Palaemonidae)

Abstract Nanomaterials (NMs) mainly settle on bottom sediments and accumulate in the benthos of aquatic communities. Decapod crustaceans, being deposit-omnivorous feeders, are appropriate biological models to assay the biological effects of NMs. The present study evaluated the effects of ZnO and multi-walled carbon nanotubes (MWCNTs) NMs separately and in combination on the activities of antioxidant enzymes on crustacean hyperglycemic hormone (CHH), hematology, reproductive performance, and hepatopancreas lesions the Oriental river prawn, Macrobrachium nipponense De Haan, 1849 [De Haan, 1833–1850]. We essayed concentrations of ZnO (0, 1, 10, 30, 50 mg l–1) and MWCNTs (0, 5, 10, 15, 20 mg l–1) and two higher concentrations of the NMs were compared in combined treatments. Both NMs showed dose-dependent effects on reproductive parameters of M. nipponense, especially the fertilization rate of eggs. Inter-molt and inter-spawn periods were postponed and reproduction stopped in 50 ppm ZnO and 15 and 20 ppm MWCNTs treatments. Our findings showed that the release of crustacean hyperglycemic hormone (CHH) and superoxide dismutase (SOD) enzyme activity are directly related to the NMs levels independently as well as in combination. NMs did not show any effect on the activities of alanine transaminase (ALT) and aspartate transaminase (AST) enzymes in muscle tissue independently, but the combined effects of the activities of these enzymes were significant. NMs caused hepatocyte enlargement, melanization, apoptosis, and necrosis damages in the hepatopancreas of prawns. The findings showed that ZnO and MWCNTs NMs have strong adverse biological effects on M. nipponense, and that this species is an appropriate bio-indicator and bio-monitor organism for NMs contaminations in the freshwater aquatic environments.

Effects of multiwalled carbon nanotube and Bacillus atrophaeus application on crop root zone thermal characteristics of saline farmland

Presently, the effects of crop roots on crop root zone thermal characteristics are poorly understood, and new fertilizers are rarely considered from the perspective of changing crop root zone thermal characteristics. This study explored the effect of applying two new fertilizers, multiwalled carbon nanotubes (MWCNTs) and Bacillus atrophaeus (B. atrophaeus), on the crop root zone thermal characteristics of saline farmland soils through in situ measurements. The results showed that MWCNTs and B. atrophaeus could indirectly affect crop root zone thermal characteristics by changing the crop root growth. Combined application of MWCNTs and B. atrophaeus could promote both to induce positive effects, promote crop root growth, and significantly alleviate the adverse effects of soil salinization. The thermal conductivity and heat capacity of the shallow root zone were reduced due to the presence of crop roots, while the opposite was true in the deep root zone. For example, the thermal conductivity of the 0–5 cm rich root zone in the MWCNT treatment was 0.8174 W m−1 ·K−1, and the thermal conductivity of the poor root zone was 13.42% higher than that of the rich root zone. MWCNTs and B. atrophaeus can also change the spatial distribution of soil moisture, soil salt, and soil particle size characteristics by influencing the root-soil interactions and indirectly affecting crop root zone thermal characteristics. In addition, MWCNTs and B. atrophaeus could directly affect the root zone thermal characteristics by changing the soil properties. The higher the soil salt content was, the more obvious the effect of the MWCNTs and B. atrophaeus on the crop root zone thermal characteristics. The thermal conductivity and heat capacity of the crop root zone were positively correlated with the soil moisture content, soil salt content and soil particle specific surface area and negatively correlated with the soil particle size and the fresh and dry root weights. In summary, MWCNTs and B. atrophaeus significantly affected crop root zone thermal characteristics directly and indirectly and could adjust the temperature of the crop root zone.

Qualitative Assessment of MWCNT- Treated Grains of Some Food Cereals

Abstract: The advancement in nanotechnology and its utilisation in agriculture increases agricultural output. To protect crops from numerous plant diseases and pests, excessive chemical, pesticide, and fungicide use can be replaced with nanoparticles. The first step of plant growth, seed germination, is thought to be the most delicate time in a plant's life cycle. The effects of carbon nanotubes on seed quality and seed content both before and after treatment are discussed in this study. Rice, wheat, and oat grains were compared with the seeds harvested from MWCNT (multiwalled carbon nanotubes) treated plants at three different concentrations (70, 80, and 90μg/ml) and indicated no significant changes in various components such as carbohydrates, protein, crude fat, crude fibre, moisture and ash contents when compared to untreated grains. Grain primed with MWCNT before sowing resulted in no change in the above components, but an increase in mineral accumulation was found. Here, we noticed a significant increase in grain yield. The treatment of MWCNT enhanced the growth of grains count by two folds compared to the control plant. The wheat grain had a moisture content: 9.3-9.38%, ash content: 1.31-1.35%, crude fat: 0.9-0.93%, crude fibre: 1.1-1.13%, protein content: 9.2-9.38%, carbohydrate content: 77.96-78.04%. The rice grain had a moisture content: 9.98-10.25%, ash content: 0.42-0.45%, crude fat: 1.00-1.02%, crude fibre: 0.9-0.93%, protein content: 4.42-4.49%, carbohydrate content: 82.92-83.03%. The oat grain had a moisture content: 8.95-9.3%, ash content: 1.74-1.8%, crude fat: 2.1-2.3%, crude fibre: 5.1-5.27%, protein content: 9.5-9.59%, carbohydrate content: 71.78-72.23%. The study revealed that the examined MWCNT concentrations might efficiently enhance the grain yield without altering the grain quality.

NO2 Sensing Behavior of Compacted Chemically Treated Multi-Walled Carbon Nanotubes.

This article is devoted to the investigation of the sensing behavior of chemically treated multi-walled carbon nanotubes (MWNTs) at room temperature. Chemical treatment of MWNTs was carried out with a solution of either sulfuric or chromic acids. The materials obtained were investigated by transmission electron microscopy, scanning electron microscopy, Raman-spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The active layer of chemiresistive gas sensors was obtained by cold pressing (compaction) at 11 MPa of powders of bare and treated multi-walled carbon nanotubes. The sensing properties of pellets were investigated using a custom dynamic type of station at room temperature (25 ± 2 °C). Detection of NO2 was performed in synthetic air (79 vol% N2, 21 vol% O2). It was found that the chemical treatment significantly affects the sensing properties of multi-walled carbon nanotubes, which is indicated by increasing the response of the sensors toward 100–500 ppm NO2 and lower concentrations.

Effect of chemical treatment of multi-walled carbon nanotubes on the specific capacitance of supercapacitors

To date, the research on carbon nanomaterials has progressed rapidly. More than 400 papers were written in 2021 on the application of carbon nanomaterials in various fields. The high demand for the use of such materials has increased due to a sharp increase in the demand for semiconductor materials and materials for supercapacitor electrodes and other electrical devices. Despite the unique physical properties of carbon nanomaterials, there are limitations to their use. To solve this problem, various methods of modifying the surface, both through chemical interactions and physical adsorption, were proposed. One of these methods is chemical modification. The evaluation of effect of chemical treatment parameters on the properties of carbon nanomaterials is an urgent task due to the fact that the chemistry of the processes is poorly understood. In this work, the effect of concentrated sulfuric and nitric acids on the change of specific surface area, elemental composition, composition of functional groups, and also on the change of specific capacitance was considered. It is believed that both the porosity and the functional groups formed during oxidation contribute to the change in specific capacitance. The specific surface area of all samples decreased on average by a factor of 1.5–3 after the chemical treatment. Different oxygen and sulfur-containing functional groups are observed after the chemical treatment. The highest specific capacitance of the treated carbon nanofibers was 114 F/g.

Pre-Harvest Application of Multi-Walled Carbon Nanotubes Improves the Antioxidant Capacity of ‘Flame Seedless’ Grapes during Storage

As a widely distributed fruit, grapes are susceptible to oxidative damage during storage and transportation, resulting in declining quality and commodity value. This study aimed to investigate the effects of preharvest application of different concentrations of multi-walled carbon nanotubes (MWCNTs) on the postharvest quality of ‘Flame Seedless’ grapes. The results showed that low-concentration (25 and 50 mg L−1) MWCNTs treatments maintained the comprehensive quality index, firmness, soluble sugar, titratable acid, pH value, and ascorbic acid (AsA) content of grapes. MWCNTs at 25 and 50 mg L−1 increased the activities of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), and ascorbic acid (APX). Furthermore, MWCNTs reduced the malondialdehyde (MDA) content and decreased the accumulation of excessive reactive oxygen species (ROS) in grape peel and pulp tissues. In addition, transmission electron microscopy (TEM) images demonstrated that MWCNTs were absorbed by parenchymal cells in the grape peel and pulp through the epidermal cell layer. MWCNTs with a specific concentration can be used as a new inducer for the biosynthesis of antioxidants to reduce oxidative damage in grapes during storage.

Vascular toxicity of multi-walled carbon nanotubes targeting vascular endothelial growth factor

Multiwalled carbon nanotubes (MWCNTs) are currently widely used and are expected to be used as drug carriers and contrast agents in clinical practice. Previous studies mainly focused on their lung toxicity; therefore, their effects on the vascular endothelium are unclear. In this study, a human angiogenesis array was used to determine the effect of MWCNTs on the expression profile of angiogenic factors in endothelial cells and to clarify the role of vascular endothelial growth factor (VEGF) in MWCNT-induced endothelial cell injury at the cellular and animal levels. The results indicated that MWCNTs (20–30 nm and 30–50 nm) could enter endothelial cells and disrupt human umbilical vein endothelial cell (HUVECs) activity in a concentration-dependent manner. MWCNTs disrupted the tube formation ability and cell migration function of HUVECs. The results from a Matrigel Plug experiment in mice showed that angiogenesis in the MWCNT experimental group was significantly reduced. The results of a protein chip analysis indicated that VEGF expression in the MWCNT treatment group was decreased, a finding that was validated by ELISA results. The protein expression levels of AKT and eNOS in the MWCNT treatment group were significantly decreased; the administration of recombinant VEGF significantly alleviated the migration ability and tube formation ability of endothelial cells injured by MWCNTs, upregulated the protein expression of AKT and eNOS, and increased the number of neovascularization in mice in the MWCNT treatment group. This study demonstrated that MWCNTs affect angiogenesis via the VEGF-Akt-eNOS axis which can be rescued by VEGF endothelial treatment.

Induction of ALOX5 during Polarization of M1 Macrophages by Multi‐walled Carbon Nanotubes

Fibrogenic carbon nanotubes (CNTs) induce the polarization of M1 and M2 macrophages in mouse lungs. Polarization of the macrophages differentiates the production of proinflammatory and pro‐resolving lipid mediators (LMs) to mediate acute inflammation and its resolution in a time‐dependent manner. In the present study, we examined the molecular mechanism by which multi‐walled CNTs (MWCNTs) induce M1 polarization in vitro, with focus on induction of arachidonate 5‐lipoxygenase (ALOX5), which is required to produce proinflammatory LMs, such as leukotriene B4 (LTB4). Treatment of J774A.1 macrophages with MWCNTs at a concentration of 2.5 µg/mL increased the expression of ALOX5 mRNA by 2.0‐fold at 1‐day and 2.5‐fold at 3‐day post‐exposure. At a concentration of 10 µg/mL, MWCNTs increased the ALOX5 mRNA expression by 3.5‐fold at 1‐day and 5.0‐fold at 3‐day post‐exposure. Immunoblotting shows that MWCNTs significantly increased the ALOX5 protein expression in macrophages. Luciferase reporter assays with the mouse ALOX5 promoter of 2 kilobase upstream of translation start codon demonstrate that the ALOX5 promoter activity increased more than 5‐fold over background. This activity was significantly elevated following 5’‐deletion analyses of ALOX5 promoter and further enhanced by MWCNT treatment, implicating a transcriptional mechanism in the induction of ALOX5. MWCNTs preferentially induced the expression of CD68, a cell surface marker of M1, by 2.5‐fold and induction was persistently high to 3‐day post‐exposure. Moreover, both the expression and activity of the inducible nitric oxide synthase, an intracellular marker of M1 macrophages, were increased by MWCNTs, indicating induction of M1 polarization. Consistent with this notion, MWCNTs increased the capacity of the macrophages to produce proinflammatory cytokines, such as tumor necrosis factor‐α (TNF‐α) and interleukin‐1β (IL‐1β), and proinflammatory LMs, such as LTB4 and prostaglandin E2 (PGE2), as measured by enzyme‐linked immunosorbent assays. Taken together, these results support that persistent exposure to MWCNTs polarizes macrophages to M1 cells with induction of ALOX5 and elevated production of proinflammatory LMs to boost the acute inflammatory response to fibrogenic nanoparticles.

Multi-walled carbon nanotubes enhanced the antioxidative system and alleviated salt stress in grape seedlings

To enhance the salt resistance of seeds and seedlings for grapes under salt stress, multi-walled carbon nanotubes (MWCNTs) at 30, 60, 90, 150, and 180 μg/mL, respectively, were used to treat gape seedlings, and the seed germination and physiological characteristics grape seedlings were studied. MWCNTs at 90 μg/mL exhibited the best results, increased root length and germination rate compared with other concentrations. Moreover, MWCNTs at 90 μg/mL mostly decreased the content of MDA in leaves and increased the activities of superoxide (SOD), peroxidase (POD), and catalase (CAT). At the same time, it increased the activities of dehydroascorbate reductase (DHAR), ascorbate peroxidase (APX), glutathione-S-transferase (GT), and glutathione reductase (GR). MWCNTs treatment also maintained the scavenging activity of DPPH· and increased the ratios of GSH:GSSG and AsA:DHA. These results suggested that MWCNTs with the appropriate concentration of 90 μg/mL could significantly enhance the reducing ability through direct and indirect antioxidant systems (the AsA-GSH cycle) and maintain a high antioxidant capacity of grape seedlings under salt stress.

Serotonin electrochemical detection in tomatoes at MWCNT-AONP nanocomposite modified electrode

This work reports on the successful synthesis of antimony oxide nanoparticles (AONPs) by hydrothermal method, acid treatment of multi-walled carbon nanotubes (f-MWCNTs), and fabrication of a MWCNT-AONP nanocomposite on screen-printed carbon electrodes (SPCE) to detect serotonin (5-HT) in tomatoes. The synthesized nanomaterials were all characterized with x-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV–vis) spectroscopy, and transmission electron microscopy (TEM). The electro-analytic and electrocatalytic experiments were performed utilizing square wave voltammetry (SWV) and cyclic voltammetry (CV) methods. The SPCE-MWCNT-AONP modified electrodes showed better electron transport and improved current response towards detection of 5-HT when compared to other electrodes studied. The current response decreased in this manner, the SPCE-MWCNT-AONP (84.13 μA) > SPCE-fMWCNTs (33.49 μA) > SPCE-AONPs (24.40 μA) > SPCE-bare (2.89 μA). The sensitivity, limit of detection (LoD) and limit of quantification (LoQ) for the SPCE-MWCNT-AONP modified electrode towards 5-HT detection was 0.2863 μA μM−1, 24 .6 nM, and 74 nM respectively, with linearity from 0.016–0.166 μM (R2 = 0.9851) utilizing SWV. The acquired LoD value for the proposed sensor compared favorably with other chemically modified electrodes from literature. Furthermore, the proposed sensor showed good reproducibility and excellent anti-interference behavior. Real-sample analysis of 5-HT in tomatoes showed excellent recoveries ranging from 91.32 to 108.28%, with an average RSD (%) value of 2.57 (n = 3). The obtained results strongly suggest that the proposed novel sensor could be applicable in diagnosing point-of-care diseases and therapeutics.

Multi-walled carbon nanotubes prevent high temperature-induced damage by activating the ascorbate-glutathione cycle in Paeonia ostii T. Hong et J. X. Zhang

Multi-walled carbon nanotubes (MWCNTs) are considered important nanomaterials with rapidly growing applications. They are inevitably released into the environment, which has attracted considerable attention for their potential threats to ecosystems. In this study, Paeonia ostii T. Hong et J. X. Zhang was exposed to MWCNTs at different concentrations under high temperature. The results showed that high temperature-induced P. ostii damage was prevented by MWCNTs, and 200 mg/L was the most effective concentration. First, MWCNTs prevented increases in reactive oxygen species, relative electrical conductivity and free proline content, and reduced decreases in SPAD, chlorophyll and carotenoid contents. Moreover, the ascorbate-glutathione (ASA-GSH) cycle was activated in response to the MWCNTs treatments, whereas the superoxide dismutase and catalase activities were inhibited. And the MWCNTs treatments also resulted in higher photosynthesis and more intact anatomical structures. Furthermore, the metabolome also confirmed that the ASA-GSH cycle played a critical role in P. ostii high-temperature tolerance, and other biological processes also responded to the MWCNTs treatments. Additionally, the genes involved in the P. ostii ASA-GSH cycle were highly expressed in response to the MWCNTs treatments. These results elucidated the beneficial role of MWCNTs in P. ostii growth under high temperature.

When nanoparticle and microbes meet: The effect of multi-walled carbon nanotubes on microbial community and nutrient cycling in hyperaccumulator system

Carbon nanotubes can potentially stimulate phytoremediation of heavy metal contaminated soil by promoting plant biomass and root growth. Yet, the regulating mechanism of carbon nanotubes on the rhizosphere microenvironment and their potential ecological risks remain poorly characterized. The purpose of this study was to systematically evaluate the effects of multi-walled carbon nanotubes (MCNT) on the diversity and structure of rhizosphere soil bacterial and fungal communities, as well as soil enzyme activities and nutrients, in Solanum nigrum L. (S. nigrum)-soil system. Here, S. nigrum were cultivated in heavy metal(loid)s contaminated soils applied with MCNT (100, 500, and 1000 mg kg-1 by concentration, none MCNT addition as control) for 60 days. Our results demonstrated more significant urease, sucrase, and acid phosphatase activities in MCNT than in control soils, which benefit to promoting plant growth. Also, there were significant reductions in available nitrogen and available potassium contents with the treatment of MCNT, while the organic carbon and available phosphorus were not affected by MCNT application. Notably, the alpha diversity of bacterial and fungal communities in the MCNT treatments did not significantly vary relative to control. However, the soil microbial taxonomic compositions were changed under the application of MCNT. Compared to the control, MCNT application increased the relative abundances of the Micrococcaceae family, Solirubrobacteraceae family, and Conexibacter genus, which were positively correlated with plant growth. In addition, the non-metric multidimensional scaling (NMDS) analysis revealed that the community structure of bacterial and fungal communities did not significantly change among all the treatments, and bacterial community structure was significantly correlated with soil organic carbon. At the same time, sucrase activity had the highest relation to fungal community structure. This study highlighted soil microbes have strong resistance and adaptation ability to carbon nanotubes with existence of plants, and revealed linkage between the rhizosphere microenvironment and plant growth, which well improved our understanding of carbon nanotubes in heavy metal phytoremediation.

Nanomaterial-aided seed regeneration in the global warming scenario: multiwalled carbon nanotubes, gold nanoparticles and heat-aged maize seeds

Seeds in soil seed-banks count amongst organisms that are the most vulnerable to the extreme temperatures predicted in certain models of global warming. This work aims to examine the possibility of a nanomaterial-aided resuscitation of heat-damaged hybrid maize (Zea mays L. “Albatross”) seeds through a study of their germinability and growth after high heat exposures. Heat energy at constant ‘dose’ was delivered at the three temperatures of 40, 50 and 60 °C (40–60) and at a much higher dose at 60 °C (+). Seed germinability and seedling growth indices were studied in the presence/absence of multiwalled carbon nanotubes (MWCNT) and our laboratory synthesised and characterised (SEM, DLS, FTIR, UV–Vis) gold nanoparticles (AuNP). Overall, the MWCNT outperformed the AuNP. The seemingly erratic germination outcomes were rationalised from the standpoint of the biomechanics of water entry into seeds with heat-damaged seedcoats. Ficksian diffusion calculations applied to the interstitial channels of the seedcoat and cellwall showed that the former but not the latter, was an effective barrier to MWCNT entry and that both easily allowed water entry. The MWCNT treatments appear to catalyse the recovery of the (+) seeds and seedlings, promote biomass and the root-to-shoot water transport, whilst the parabolic biomass trend for 40–60 suggests opposing temperature-regulated factors possibly involving reactive oxygen species. Summarising, growth indices of heat-damaged seeds show a strong non-monotonic dose dependence where the MWCNT significantly altered the response, catalysing the recovery of the high heat ‘dose’ set. These results hold promise for the application of nano-biotechnology to agriculture in the global warming scenario.

Small structures with big impact: Multi-walled carbon nanotubes enhanced remediation efficiency in hyperaccumulator Solanum nigrum L. under cadmium and arsenic stress

With the fast development of nanotechnology, nanomaterials are being increasingly applied for the remediation of contaminated soils. However, few researches have been reported on the complex interactions of carbon nanotubes with heavy metal (loid)s in phytoremediation. Here, we conduct a pot experiment to investigate the effects of multi-walled carbon nanotubes (MWCNTs) on the plant growth and behavior of heavy metal (loid)s in hyperaccumulator-soil system. Cd hyperaccumulator Solanum nigrum L. (S. nigrum) were cultivated in Cadmium (Cd) and Arsenic (As) contaminated soils amended with MWCNTs at 100, 500, and 1000 mg kg−1 for 60 days, respectively. The application of MWCNTs increased the shoot length and plant dry biomass by 5.56%∼25.13% and 5.23%∼27.97%. Whereas, root and leaf growth were inhibited in 1000 mg kg−1 MWCNTs treatments. Meanwhile, MWCNTs at 500 mg kg−1 significantly enhanced the accumulation of heavy metal (loid)s in S. nigrum（18.29% for Cd and 32.47% for As）and alleviated co-contamination induced toxicity, by motivating plant growth, stimulating antioxidant enzymatic activities, and increasing micronutrient content (p < 0.05). The bio-concentration factor of As was decreased (15.31–28.08%) under MWCNTs application, which plays an important role in the alleviation of phytotoxicity. Besides, bioavailable Cd and As were reduced in rhizosphere soils, and the most significant reduction (16.29% for Cd and 8.19% for As) were shown in 500 mg kg−1 MWCNTs treatment. These findings demonstrate that suitable concentration of MWCNTs can enhance remediation efficiency. Our study gives a strong evidence to promote the phytoremediation for co-contaminated soils by using nanomaterials.

Mechanical properties of carbon nanotubes/epoxy nanocomposites: Pre-curing, curing temperature, and cooling rate

The effects of composite fabrication, such as pre-curing, curing temperature, and cooling rate, were studied. In this work, the pre-curing was defined as heat treatment of Multi-Walled Carbon Nanotubes (MWNCTs) with Diglycidyl Ether of Bisphenol A (DGEBA) epoxy resin. Acid purified MWCNTs were characterized by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). The pre-curing facilitated bonding between MWCNTs and epoxy via the oxirane ring of DGEBA, which accelerated the curing process of epoxy and increased mechanical properties. The elevated curing temperature on the pre-cured sample further improved the composite’s mechanical properties by increasing interfacial bonding due to cross-linking. The rapid cooling using liquid nitrogen during pre-curing treatment prevented re-agglomeration of MWCNTs, showing smaller agglomerates and improving the mechanical properties. Agglomeration was characterized by scanning electron microscopy, while the bonding between MWCNTs and epoxy was examined by the length of fibre pull-out on the fracture surface. Tensile testing was deployed for mechanical properties characterization. The degree of cure was determined by FTIR and Differential Thermal Analysis (DTA).