Enhanced Interfacial Strength and UV Shielding of Aramid Fiber Composites through ZnO Nanoparticle Sizing

Here, a simple zinc oxide (ZnO) nanoparticle sizing is reported for aramid fibers that simultaneously provides interfacial reinforcement and UV absorption to develop improved fiber-reinforced composites. Through a one-step nanoparticle deposition, the modified aramid fiber showed an increase in interfacial shear strength of 18.9% with the addition of ZnO nanoparticles when tested by single-fiber pullout. The aramid fibers were then treated with a hydrolysis process common to aramid fibers to oxidize the surface and elucidate the importance of oxygen functional groups at the interface. These oxidized fibers proved to further enhance the interface between the fiber surface and nanoparticle, leading to a 33.3% increase relative to the bare fiber. Additionally, due to the absorption properties of ZnO, the retainment of mechanical properties of coated fibers was determined after exposure to an artificial UV light source. After 24 h of exposure, fibers coated with ZnO nanoparticles retained 25% more tensile strength and 21% more modulus than uncoated bare fibers. This work shows that ZnO nanoparticles may serve as a novel, yet simple, multifunctional fiber sizing with which to increase the interfacial strength of aramid fiber composites and improve the resistance to UV irradiation, enabling stronger and more-durable structural fiber composites.

Zinc Oxide Flower-Like Nanostructures That Exhibit Enhanced Toxicology Effects in Cancer Cells

Nanostructured zinc oxide (ZnO) materials have been intensively studied because of their potential applications in cancer therapies. However, a better comprehension of the toxicity of the flower-like ZnO nanostructures toward cancer cells is still needed. In this study, we investigate the cytotoxicity of a ZnO flower-like nanostructure produced at low temperature via aqueous solution in human cervical carcinoma (HeLa) cells and noncancerous cell-line murine fibroblast (L929) cells. Nanotoxicology effects were analyzed to study apoptosis and necrosis processes, reactive oxygen species production, and cellular uptake. Cells remained incubated for 24 h in concentrations of 0.1, 1.0, and 10.0 μg mL^-1 ZnO nanoparticles (NPs), with the estimated rods length varying from 1.7 ± 0.4 to 2.3 ± 0.4 μm, synthesized at different times (4, 2, and 0.5 h) by an aqueous solution method. The cytotoxic response observed in noncancerous and cancer cells showed that all of the ZnO NPs synthesized by an aqueous solution exhibited enhanced toxicology effects in cancer cells. ZnO flower-nanostructures exhibited a higher cytotoxic against cancer HeLa cells, in comparison to the noncancerous cell line L929. The cytotoxic response of ZnO NPs at 0.5, 2, and 4 h in L929 cells was not statistically significant. This ability may be of clinical interest because of the effectiveness of ZnO NPs to distinguish between normal and cancer cells in cancer therapy.

Green synthesis of ZnO nanoparticles by Olive (Olea europaea)

Green synthesis of nanoparticles is superior to physical and chemical methods as it is environment-friendly and cost-effective. The present study was carried out for inducing nanoparticles synthesis by zinc nitrate in the leaves extracts of olive. Further leaves extracts were evaluated for antiradical scavenging activity by 1, 1-diphenyl-2-picryl-hydrazyl assay. Morphological and structural properties of the synthesised ZnO nanoparticles have been characterised using UV-Vis spectrophotometer, FTIR, TEM, XRD and dynamic light scattering (DLS) analysis. Further, zinc oxide nanoparticles were evaluated for antiradical scavenging activity by capacity of total antioxidant assay. Synthesised ZnO nanoparticles were confirmed by the absorption maxima at the wavelength of 370 nm. TEM image revealed that ZnO nanoparticles were spherical with average size 41 nm. FTIR investigation suggested that the flavonoids, glycosides, proteins and phenols molecules can play an important role in the stabilisation of ZnO nanoparticles.

Nano Zinc Oxide Inhibits Fibrillar Growth and Suppresses Cellular Toxicity of Lysozyme Amyloid

Deposition of amyloid fibers has been a common pathological event in many neurodegenerations, such as Alzheimer's disease, Parkinson's disease, and Prion disease. Although various therapeutic interventions have been reported, nanoparticles have recently been considered as possible inhibitors of amyloid fibrillation. Here, we reported the effect of three different forms of zinc oxide nanoparticles (ZnONP): uncapped (ZnONP_uncap), starch-capped (ZnONP_ST), and self-assembled (ZnONP_assmb) (average sizes of 10, 30, and 163 nm, respectively), having a core size of 10-15 nm, in the amyloid growth of hen egg white lysozyme (HEWL). We monitored the amyloid growth by electron microscopy as well as Thioflavin-T (ThT) measurement. We observed that ZnONP demonstrated a dose-dependent inhibition of fibrillar amyloid growth of HEWL, with the greatest effect being exhibited by ZnONP_ST. Such inhibition was also associated with a decrease in cross β-sheet amount, surface hydrophobicity as well as increase of stability of proteins. Furthermore, we observed that ZnONP_ST prolonged the nucleation phase and shortened the elongation phase of HEWL amyloid growth. Although pure amyloid caused profound cellular toxicity in both mouse carcinoma N2a and normal cells such as human keratinocytes HaCaT cells, amyloid formed in the presence of ZnONP showed much reduced cellular toxicity. We also observed that the inhibition of amyloid growth was effective when ZnONP was administered during the lag phase. When our amyloid inhibition results were compared with a well-known inhibitor curcumin, we observed that ZnONP_ST demonstrated a better inhibitory effect than curcumin. Overall, here, we reported the inhibitory activity of three different forms of ZnONP to amyloid fibrillation of HEWL and amyloid-mediated cytotoxicity to different extents, while starch-capped ZnONP showed the highest fibrillation inhibitory effect.

Determination of zinc oxide nanoparticles toxicity in root growth in wheat (Triticum aestivum L.) seedlings

The effect of zinc oxide nanoparticles (ZnONPs) was studied in wheat (Triticum aestivum L.) seedlings under in vitro exposure conditions. To avoid precipitation of nanoparticles, the seedlings were grown in half strength semisolid Murashige and Skoog medium containing 0, 50, 100, 200, 400 and 500 mg L(-1) of ZnONPs. Analysis of zinc (Zn) content showed significant increase in roots. In vivo detection using fluorescent probe Zynpyr-1 indicated accumulation of Zn in primary and lateral root tips. All concentrations of ZnONPs significantly reduced root growth. However, significant decrease in shoot growth was observed only after exposure to 400 and 500 mg L(-1) of ZnONPs. The reactive oxygen species and lipid peroxidation levels significantly increased in roots. Significant increase in cell-wall bound peroxidase activity was observed after exposure to 500 mg L(-1) of ZnONPs. Histochemical staining with phloroglucinol-HCl showed lignification of root cells upon exposure to 500 mg L(-1) of ZnONPs. Treatment with propidium iodide indicated loss of cell viability in root tips of wheat seedlings. These results suggest that redox imbalances, lignification and cell death has resulted in reduction of root growth in wheat seedlings exposed to ZnONPs nanoparticles.

Targeted Cancer Therapy: Correlative Light-Electron Microscopy Shows RGD-Targeted ZnO Nanoparticles Dissolve in the Intracellular Environment of Triple Negative Breast Cancer Cells and Cause Apoptosis with Intratumor Heterogeneity (Adv. Healthcare Mater. 11/2016)

On page 1310 J. S. Merzaban, A. E. Porter, and co-workers present fluorescently labeled RGD-targeted ZnO nanoparticles (NPs; green) for the targeted delivery of cytotoxic ZnO to integrin αvβ3 receptors expressed on triple negative breast cancer cells. Correlative light-electron microscopy shows that NPs dissolve into ionic Zn(2+) (blue) upon uptake and cause apoptosis (red) with intra-tumor heterogeneity, thereby providing a possible strategy for targeted breast cancer therapy. Cover design by Ivan Gromicho.

Correlative Light-Electron Microscopy Shows RGD-Targeted ZnO Nanoparticles Dissolve in the Intracellular Environment of Triple Negative Breast Cancer Cells and Cause Apoptosis with Intratumor Heterogeneity

ZnO nanoparticles (NPs) are reported to show a high degree of cancer cell selectivity with potential use in cancer imaging and therapy. Questions remain about the mode by which the ZnO NPs cause cell death, whether they exert an intra- or extracellular effect, and the resistance among different cancer cell types to ZnO NP exposure. The present study quantifies the variability between the cellular toxicity, dynamics of cellular uptake, and dissolution of bare and RGD (Arg-Gly-Asp)-targeted ZnO NPs by MDA-MB-231 cells. Compared to bare ZnO NPs, RGD-targeting of the ZnO NPs to integrin αvβ3 receptors expressed on MDA-MB-231 cells appears to increase the toxicity of the ZnO NPs to breast cancer cells at lower doses. Confocal microscopy of live MDA-MB-231 cells confirms uptake of both classes of ZnO NPs with a commensurate rise in intracellular Zn(2+) concentration prior to cell death. The response of the cells within the population to intracellular Zn(2+) is highly heterogeneous. In addition, the results emphasize the utility of dynamic and quantitative imaging in understanding cell uptake and processing of targeted therapeutic ZnO NPs at the cellular level by heterogeneous cancer cell populations, which can be crucial for the development of optimized treatment strategies.

Decoupling the Direct and Indirect Biological Effects of ZnO Nanoparticles Using a Communicative Dual Cell-Type Tissue Construct

While matter at the nanoscale can be manipulated, the knowledge of the interactions between these nanoproducts and the biological systems remained relatively laggard. Current nanobiology study is rooted on in vitro study using conventional 2D cell culture model. A typical study employs monolayer cell culture that simplifies the real context of which to measure any nanomaterial effect; unfortunately, this simplification also demonstrated the limitations of 2D cell culture in predicting the actual biological response of some tissues. In fact, some of the characteristics of tissue such as spatial arrangement of cells and cell-cell interaction, which are simplified in 2D cell culture model, play important roles in how cells respond to a stimulus. To more accurately recapitulate the features and microenvironment of tissue for nanotoxicity assessments, an improved organotypic-like in vitro multicell culture system to mimic the kidney endoepithelial bilayer is introduced. Results showed that important nano-related parameters such as the diffusion, direct and indirect toxic effects of ZnO nanoparticles can be studied by combining this endoepithelial bilayer tissue model and traditional monolayer culture setting.

Zinc-Oxide Nanoparticles Exhibit Genotoxic, Clastogenic, Cytotoxic and Actin Depolymerization Effects by Inducing Oxidative Stress Responses in Macrophages and Adult Mice

Zinc oxide nanoparticles (ZnO-NPs) have wide biological applications, which have raised serious concerns about their impact on the health and environment. Although, various studies have shown ZnO-NP toxicity on different cells underin vitroconditions, sufficient information is lacking regarding toxicity and underlying mechanisms underin vivoconditions. In this work, we investigated genotoxic, clastogenic, and cytotoxic effects of ZnO-NPs on macrophages and in adult mice. ZnO-NP-treated mice showed signs of toxicity such as loss in body weight, passive behavior and reduced survival. Further mechanistic studies revealed that administration of higher dose caused severe DNA damage in peripheral blood and bone marrow cells as evident by the formation of COMET tail, micronuclei, chromosomal fragmentation, and phosphorylation of H2A histone family member X. Moreover, ZnO-NPs inhibited DNA repair mechanism by downregulating the expression offen-1andpolBproteins. Histopathological examinations showed severe inflammation and damage to liver, lungs, and kidneys. Cell viability and wound healing assays revealed that ZnO-NPs killed macrophages in a dose-dependent manner, caused severe wounds and inhibited cellular migration by irreversible actin depolymerization and degradation. Reduction in the viability of macrophages was due to the arrest of the cell cycle at the G0/G1 phase, inhibition of superoxide dismutase and catalase and eventually reactive oxygen species. Furthermore, treatment with an antioxidant drug N-acetyl cysteine significantly reduced the ZnO-NP induced genotoxicity bothin vitroandin vivo Altogether, this study gives detailed pathological insights of ZnO-NP that impair cellular functions, thus will enable to arbitrate their biological applications.

Brassinosteroid Ameliorates Zinc Oxide Nanoparticles-Induced Oxidative Stress by Improving Antioxidant Potential and Redox Homeostasis in Tomato Seedling

In the last few decades use of metal-based nanoparticles (MNPs) has been increased significantly that eventually contaminating agricultural land and limiting crop production worldwide. Moreover, contamination of food chain with MNPs has appeared as a matter of public concern due to risk of potential health hazard. Brassinosteroid has been shown to play a critical role in alleviating heavy metal stress; however, its function in relieving zinc oxide nanoparticles (ZnO NPs)-induced phytotoxicity remains unknown. In this study, we investigated the potential role of 24-epibrassinolide (BR) in mitigating ZnO NPs-induced toxicity in tomato seedlings. Seedling growth, biomass production, and root activity gradually decreased, but Zn accumulation increased with increasing ZnO NPs concentration (10-100 mg/L) in growth media (½ MS). The augmentation of BR (5 nM) in media significantly ameliorated 50 mg/L ZnO NPs-induced growth inhibition. Visualization of hydrogen peroxide (H2O2), and quantification of H2O2 and malondialdehyde (MDA) in tomato roots confirmed that ZnO NPs induced an oxidative stress. However, combined treatment with BR and ZnO NPs remarkably reduced concentration of H2O2 and MDA as compared with ZnO NPs only treatment, indicating that BR supplementation substantially reduced oxidative stress. Furthermore, the activities of key antioxidant enzymes such as superoxide dismutase (SOD), catalase, ascorbate peroxidase and glutathione reductase were increased by combined treatment of BR and ZnO NPs compared with ZnO NPs only treatment. BR also increased reduced glutathione (GSH), but decreased oxidized glutathione (GSSG)] and thus improved cellular redox homeostasis by increasing GSH:GSSG ratio. The changes in relative transcript abundance of corresponding antioxidant genes such as Cu/Zn SOD, CAT1, GSH1, and GR1 were in accordance with the changes in those antioxidants under different treatments. More importantly, combined application of BR and ZnO NPs significantly decreased Zn content in both shoot and root of tomato seedlings as compared with ZnO NPs alone. Taken together, this study, for the first time, showed that BR could not only improve plant tolerance to ZnO NPs but also reduce the excess zinc content in tomato seedlings. Such a finding may have potential implication in safe vegetable production in the MNPs-polluted areas.

Decomposition of Organometal Halide Perovskite Films on Zinc Oxide Nanoparticles

Solution processed zinc oxide (ZnO) nanoparticles (NPs) with excellent electron transport properties and a low-temperature process is a viable candidate to replace titanium dioxide (TiO2) as electron transport layer to develop high-efficiency perovskite solar cells on flexible substrates. However, the number of reported high-performance perovskite solar cells using ZnO-NPs is still limited. Here we report a detailed investigation on the chemistry and crystal growth of CH3NH3PbI3 perovskite on ZnO-NP thin films. We find that the perovskite films would severely decompose into PbI2 upon thermal annealing on the bare ZnO-NP surface. X-ray photoelectron spectroscopy (XPS) results show that the hydroxide groups on the ZnO-NP surface accelerate the decomposition of the perovskite films. To reduce the decomposition, we introduce a buffer layer in between the ZnO-NPs and perovskite layers. We find that a commonly used buffer layer with small molecule [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) can slow down but cannot completely avoid the decomposition. On the other hand, a polymeric buffer layer using poly(ethylenimine) (PEI) can effectively separate the ZnO-NPs and perovskite, which allows larger crystal formation with thermal annealing. The power conversion efficiencies of perovskite photovoltaic cells are significantly increased from 6.4% to 10.2% by replacing PC61BM with PEI as the buffer layer.

LipiD-QuanT: a novel method to quantify lipid accumulation in live cells

Lipid droplets (LDs) are the main storage organelles for triglycerides. Elucidation of lipid accumulation mechanisms and metabolism are essential to understand obesity and associated diseases. Adipogenesis has been well studied in murine 3T3-L1 and human Simpson-Golabi-Behmel syndrome (SGBS) preadipocyte cell lines. However, most techniques for measuring LD accumulation are either not quantitative or can be destructive to samples. Here, we describe a novel, label-free LD quantification technique (LipiD-QuanT) to monitor lipid dynamics based on automated image analysis of phase contrast microscopy images acquired during in vitro human adipogenesis. We have applied LipiD-QuanT to measure LD accumulation during differentiation of SGBS cells. We demonstrate that LipiD-QuanT is a robust, nondestructive, time- and cost-effective method compared with other triglyceride accumulation assays based on enzymatic digest or lipophilic staining. Further, we applied LipiD-QuanT to measure the effect of four potential pro- or antiobesogenic substances: DHA, rosiglitazone, elevated levels of D-glucose, and zinc oxide nanoparticles. Our results revealed that 2 µmol/l rosiglitazone treatment during adipogenesis reduced lipid production and caused a negative shift in LD diameter size distribution, but the other treatments showed no effect under the conditions used here.

An Investigation of the Cytotoxicity and Caspase-Mediated Apoptotic Effect of Green Synthesized Zinc Oxide Nanoparticles Using Eclipta prostrata on Human Liver Carcinoma Cells

Cancer is a leading cause of death worldwide and sustained focus is on the discovery and development of newer and better tolerated anticancer drugs, especially from plants. In the present study, a simple, eco-friendly, and inexpensive approach was followed for the synthesis of zinc oxide nanoparticles (ZnO NPs) using the aqueous leaf extract of Eclipta prostrata. The synthesized ZnO NPs were characterized by UV-visible absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), High-resolution transmission electron microscopy (HRTEM), and Selected area (electron) diffraction (SAED). The HRTEM images confirmed the presence of triangle, radial, hexagonal, rod, and rectangle, shaped with an average size of 29 ± 1.3 nm. The functional groups for synthesized ZnO NPs were 3852 cm-1 for H-H weak peak, 3138 cm-1 for aromatic C-H extend, and 1648 cm-1 for Aromatic ring stretch. The 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT), caspase and DNA fragmentation assays were carried out using various concentrations of ZnO NPs ranging from 1 to 100 mg/mL. The synthesized ZnO NPs showed dose dependent cytopathic effects in the Hep-G2 cell line. At 100 mg/mL concentration, the synthesized ZnO NPs exhibited significant cytotoxic effects and the apoptotic features were confirmed through caspase-3 activation and DNA fragmentation assays.

Morphometric and stereological assessment of the effects of zinc oxide nanoparticles on the mouse testicular tissue

OBJECTIVE

To evaluate the effects of zinc oxide nanoparticles (ZNPs) on morphometric and stereological parameters of mouse testis.

BACKGROUND

ZNPs are increasingly used in sunscreens, biosensors, food additives, pigments, rubber manufacture, and electronic materials. However, the potential toxicity of these nanoparticles is not well understood.

METHODS

Experimental Groups (ZNP-1, ZNP-2 and ZNP-3) received one of the following treatments daily for 35 days: 5, 50 and 300 mg/kg ZNPs respectively. Right testis from each animal was fixed in bouin's solution for measurement of total volume of testis, total volume of seminiferous tubules, total volume of interstitial tissue and total number of Leydig cells by stereological methods. Seminiferous tubule diameter and seminiferous epithelium height were assessed by morphometrical method. The left testicles were homogenized for measurement of testosterone concentration.

RESULTS

There was a significant decrease in the weight of testicles in ZNP-3 groups. The stereological and morphometrical parameters were significantly changed in ZNP-2 and ZNP-3 groups. ZNP-2 and ZNP-3 groups also showed a significant decrease in testosterone concentrations (p < 0.05).

CONCLUSION

This study demonstrated that ZNPs can change stereological and morphometrical parameters of the seminiferous tubules and reduce the number of Leydig cells (Tab. 3, Fig. 3, Ref. 36).

Biomimicry 3D gastrointestinal spheroid platform for the assessment of toxicity and inflammatory effects of zinc oxide nanoparticles

Our current mechanistic understanding on the effects of engineered nanoparticles (NPs) on cellular physiology is derived mainly from 2D cell culture studies. However, conventional monolayer cell culture may not accurately model the mass transfer gradient that is expected in 3D tissue physiology and thus may lead to artifactual experimental conclusions. Herein, using a micropatterned agarose hydrogel platform, the effects of ZnO NPs (25 nm) on 3D colon cell spheroids of well-defined sizes are examined. The findings show that cell dimensionality plays a critical role in governing the spatiotemporal cellular outcomes like inflammatory response and cytotoxicity in response to ZnO NPs treatment. More importantly, ZnO NPs can induce different modes of cell death in 2D and 3D cell culture systems. Interestingly, the outer few layers of cells in 3D model could only protect the inner core of cells for a limited time and periodically slough off from the spheroids surface. These findings suggest that toxicological conclusions made from 2D cell models might overestimate the toxicity of ZnO NPs. This 3D cell spheroid model can serve as a reproducible platform to better reflect the actual cell response to NPs and to study a more realistic mechanism of nanoparticle-induced toxicity.

Toxicity of 100 nm zinc oxide nanoparticles: a report of 90-day repeated oral administration in Sprague Dawley rats

Nanoparticles (NPs) are used commercially in health and fitness fields, but information about the toxicity and mechanisms underlying the toxic effects of NPs is still very limited. The aim of this study is to investigate the toxic effect(s) of 100 nm negatively (ZnO^AE100[−]) or positively (ZnO^AE100[+]) charged zinc oxide (ZnO) NPs administered by gavage in Sprague Dawley rats, to establish a no observed adverse effect level, and to identify target organ(s). After verification of the primary particle size, morphology, hydrodynamic size, and zeta potential of each test article, we performed a 90-day study according to Organisation for Economic Co-operation and Development test guideline 408. For the 90-day study, the high dose was set at 500 mg/kg and the middle and low doses were set at 125 mg/kg and 31.25 mg/kg, respectively. Both ZnO NPs had significant changes in hematological and blood biochemical analysis, which could correlate with anemia-related parameters, in the 500 mg/kg groups of both sexes. Histopathological examination showed significant adverse effects (by both test articles) in the stomach, pancreas, eye, and prostate gland tissues, but the particle charge did not affect the tendency or the degree of the lesions. We speculate that this inflammatory damage might result from continuous irritation caused by both test articles. Therefore, the target organs for both ZnO^AE100(−) and ZnO^AE100(+) are considered to be the stomach, pancreas, eye, and prostate gland. Also, the no observed adverse effect level for both test articles was identified as 31.25 mg/kg for both sexes, because the adverse effects were observed at all doses greater than 125 mg/kg.

Substrates coated with silver nanoparticles as a neuronal regenerative material

Much effort has been devoted to the design of effective biomaterials for nerve regeneration. Here, we report the novel use of silver nanoparticles (AgNPs) as regenerative agents to promote neuronal growth. We grew neuroblastoma cells on surfaces coated with AgNPs and studied the effect on the development of the neurites during the initiation and the elongation growth phases. We find that the AgNPs function as favorable anchoring sites, and the growth on the AgNP-coated substrates leads to a significantly enhanced neurite outgrowth. Cells grown on substrates coated with AgNPs have initiated three times more neurites than cells grown on uncoated substrates, and two times more than cells grown on substrates sputtered with a plain homogenous layer of silver. The growth of neurites on AgNPs in the elongation phase was enhanced as well. A comparison with substrates coated with gold nanoparticles (AuNPs) and zinc oxide nanoparticles (ZnONPs) demonstrated a clear silver material-driven promoting effect, in addition to the nanotopography. The growth on substrates coated with AgNPs has led to a significantly higher number of initiating neurites when compared to substrates coated with AuNPs or ZnONPs. All nanoparticle-coated substrates affected and promoted the elongation of neurites, with a significant positive maximal effect for the AgNPs. Our results, combined with the well-known antibacterial effect of AgNPs, suggest the use of AgNPs as an attractive nanomaterial – with dual activity – for neuronal repair studies.

Zinc oxide nanoparticles impair bacterial clearance by macrophages

AIM

The extensive development of nanoparticles (NPs) and their widespread employment in daily life have led to an increase in environmental concentrations of substances that may pose a biohazard to humans. The aim of this work was to examine the effects of zinc oxide nanoparticles (ZnO-NPs) on the host's pulmonary immune system response to nontypeable Haemophilus influenzae (NTHi) infection.

MATERIALS & METHODS

A murine infection model was employed to assess pulmonary inflammation and bacterial clearance in response to exposure to ZnO-NPs. The molecular mechanisms underlying ZnO-NP-impaired macrophage activation were investigated.

RESULTS

Treatment with ZnO-NPs impaired macrophage activation, leading to a delay in NTHi clearance in the bronchial alveolar lavage fluids and lungs. Exposure to ZnO-NPs followed by NTHi challenge decreased levels of nitric oxide compared with NTHi infection alone. The effects of ZnO-NPs involved downregulation of NTHi-activated expression of inducible nitric oxide synthase and the translocation of active NF-kB into the nucleus.

CONCLUSION

These results demonstrate that exposure to ZnO-NPs can impair innate immune responses and attenuate macrophage responses to bacterial infection.

ZnO nanoparticle-induced oxidative stress triggers apoptosis by activating JNK signaling pathway in cultured primary astrocytes

It has been documented in in vitro studies that zinc oxide nanoparticles (ZnO NPs) are capable of inducing oxidative stress, which plays a crucial role in ZnO NP-mediated apoptosis. However, the underlying molecular mechanism of apoptosis in neurocytes induced by ZnO NP exposure was not fully elucidated. In this study, we investigated the potential mechanisms of apoptosis provoked by ZnO NPs in cultured primary astrocytes by exploring the molecular signaling pathways triggered after ZnO NP exposure. ZnO NP exposure was found to reduce cell viability in MTT assays, increase lactate dehydrogenase (LDH) release, stimulate intracellular reactive oxygen species (ROS) generation, and elicit caspase-3 activation in a dose- and time-dependent manner. Apoptosis occurred after ZnO NP exposure as evidenced by nuclear condensation and poly(ADP-ribose) polymerase-1 (PARP) cleavage. A decrease in mitochondrial membrane potential (MMP) with a concomitant increase in the expression of Bax/Bcl-2 ratio suggested that the mitochondria also mediated the pathway involved in ZnO NP-induced apoptosis. In addition, exposure of the cultured cells to ZnO NPs led to phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-related kinase (ERK), and p38 mitogen-activated protein kinase (p38 MAPK). Moreover, JNK inhibitor (SP600125) significantly reduced ZnO NP-induced cleaved PARP and cleaved caspase-3 expression, but not ERK inhibitor (U0126) or p38 MAPK inhibitor (SB203580), indicating that JNK signaling pathway is involved in ZnO NP-induced apoptosis in primary astrocytes.

Metalloproteins and phytochelatin synthase may confer protection against zinc oxide nanoparticle induced toxicity in Caenorhabditis elegans

Zinc oxide nanoparticles (ZnONPs) are used in large quantities by the cosmetic, food and textile industries. Here we exposed Caenorhabditis elegans wild-type and a metal sensitive triple knockout mutant (mtl-1;mtl-2;pcs-1) to ZnONPs (0-50mg/L) to study strain and exposure specific effects on transcription, reactive oxygen species generation, the biomolecular phenotype (measured by Raman microspectroscopy) and key endpoints of the nematode life cycle (growth, reproduction and lifespan). A significant dissolution effect was observed, where dissolved ZnO constituted over 50% of total Zn within a two day exposure to the test medium, suggesting that the nominal exposure to pure ZnONPs represents in vivo, at best, a mixture exposure of ionic zinc and nanoparticles. Nevertheless, the analyses provided evidence that the metallothioneins (mtl-1 and mtl-2), the phytochelatin synthase (pcs-1) and an apoptotic marker (cep-1) were transcriptionally activated. In addition, the DCFH-DA assay provided in vitro evidence of the oxidative potential of ZnONPs in the metal exposure sensitive triple mutant. Raman spectroscopy highlighted that the biomolecular phenotype changes significantly in the mtl-1;mtl-2;pcs-1 triple knockout worm upon ZnONP exposure, suggesting that these metalloproteins are instrumental in the protection against cytotoxic damage. Finally, ZnONP exposure was shown to decrease growth and development, reproductive capacity and lifespan, effects which were amplified in the triple knockout. By combining diverse toxicological strategies, we identified that individuals (genotypes) housing mutations in key metalloproteins and phytochelatin synthase are more susceptible to ZnONP exposure, which underlines their importance to minimize ZnONP induced toxicity.

Rapid degradation of zinc oxide nanoparticles by phosphate ions

Zinc oxide nanoparticles are highly sensitive towards phosphate ions even at pH 7. Buffer solutions and cell culture media containing phosphate ions are able to destroy ZnO nanoparticles within a time span from less than one hour to one day. The driving force of the reaction is the formation of zinc phosphate of very low solubility. The morphology of the zinc oxide particles has only a minor influence on the kinetics of this reaction. Surface properties related to different production methods and the presence and absence of labelling with a perylene fluorescent dye are more important. Particles prepared under acidic conditions are more resistant than those obtained in basic or neutral reaction medium. Surprisingly, the presence of a SiO2 coating does not impede the degradation of the ZnO core. In contrast to phosphate ions, β-glycerophosphate does not damage the ZnO nanoparticles. These findings should be taken into account when assessing the biological effects or the toxicology of zinc oxide nanoparticles.

Room-temperature synthesis of zinc oxide nanoparticles in different media and their application in cyanide photodegradation

Cyanide is an extreme hazard and extensively found in the wastes of refinery, coke plant, and metal plating industries. A simple, fast, cost-effective, room-temperature wet chemical route, based on cyclohexylamine, for synthesizing zinc oxide nanoparticles in aqueous and enthanolic media was established and tested for the photodegradation of cyanide ions. Particles of polyhedra morphology were obtained for zinc oxide, prepared in ethanol (ZnOE), while spherical and some chunky particles were observed for zinc oxide, prepared in water (ZnOW). The morphology was crucial in enhancing the cyanide ion photocatalytic degradation efficiency of ZnOE by a factor of 1.5 in comparison to the efficiency of ZnOW at an equivalent concentration of 0.02 wt.% ZnO. Increasing the concentration wt.% of ZnOE from 0.01 to 0.09 led to an increase in the photocatalytic degradation efficiency from 85% to almost 100% after 180 min and a doubling of the first-order rate constant (k).

Modulation of defect-mediated energy transfer from ZnO nanoparticles for the photocatalytic degradation of bilirubin

In recent years, nanotechnology has gained significant interest for applications in the medical field. In this regard, a utilization of the ZnO nanoparticles for the efficient degradation of bilirubin (BR) through photocatalysis was explored. BR is a water insoluble byproduct of the heme catabolism that can cause jaundice when its excretion is impaired. The photocatalytic degradation of BR activated by ZnO nanoparticles through a non-radiative energy transfer pathway can be influenced by the surface defect-states (mainly the oxygen vacancies) of the catalyst nanoparticles. These were modulated by applying a simple annealing in an oxygen-rich atmosphere. The mechanism of the energy transfer process between the ZnO nanoparticles and the BR molecules adsorbed at the surface was studied by using steady-state and picosecond-resolved fluorescence spectroscopy. A correlation of photocatalytic degradation and time-correlated single photon counting studies revealed that the defect-engineered ZnO nanoparticles that were obtained through post-annealing treatments led to an efficient decomposition of BR molecules that was enabled by Förster resonance energy transfer.

Induction of oxidative stress, DNA damage, and apoptosis in a malignant human skin melanoma cell line after exposure to zinc oxide nanoparticles

The widespread use of zinc oxide (ZnO) nanoparticles worldwide exposes humans to their adverse effects, so it is important to understand their biological effects and any associated risks. This study was designed to investigate the cytotoxicity, oxidative stress, and apoptosis caused by ZnO nanoparticles in human skin melanoma (A375) cells. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide] and lactate dehydrogenase-based cell viability assays showed a significant decrease in cell viability after exposure to ZnO nanoparticles, and phase contrast images revealed that cells treated with these nanoparticles had a lower density and a rounded morphology. ZnO nanoparticles were also found to induce oxidative stress, evidenced by generation of reactive oxygen species and depletion of the antioxidant, glutathione. Induction of apoptosis was confirmed by chromosomal condensation assay and caspase-3 activation. Further, more DNA damage was observed in cells exposed to the highest concentration of ZnO nanoparticles. These results demonstrate that ZnO nanoparticles have genotoxic potential in A375 cells, which may be mediated via oxidative stress. Our short-term exposure study showing induction of a genotoxic and apoptotic response to ZnO nanoparticles needs further investigation to determine whether there may be consequences of long-term exposure to ZnO nanoparticles.

The effect of zinc oxide nanoparticles deposition for friction reduction on orthodontic wires

BACKGROUND

In the sliding technique, the reduced frictional forces are associated with rapid tooth movements and better control of the anchorage. Recently, wire coating with different nanoparticles has been proposed to decrease frictional forces. This in vitro study was carried out to coat stainless steel (SS) wires with zinc oxide (ZnO) nanoparticles in order to determine the effect of this coating on friction between wires and orthodontic brackets.

MATERIALS AND METHODS

Eighty 0.016 inch and 0.019 inch × 0.025 inch SS wires with and without ZnO nanoparticles were used in 80 orthodontic brackets (0.018 and 0.022 systems). The coated wires were analyzed by SEM and X-Ray diffraction (XRD) observations. Kinetic friction between the wires and orthodontic brackets were calculated using a universal testing machine. Frictional forces were statistically analyzed using three-way ANOVA, one-way ANOVA, Student's t-test and Tukey multiple comparison tests.

RESULTS

Coating with ZnO nanoparticles significantly influenced frictional force values (P < 0.0001). In 0.019 inch × 0.025 inch wires, the frictional forces were 1.6912 ± 0.18868 and 3.4485 ± 0.32389 N in the coated and uncoated wires respectively, (51% reductions). In the 0.016 inch wires, the friction values were estimated to be 1.5668 ± 0.10703 and 2.56 ± 0.34008 N in the coated and uncoated conditions, respectively, (39% reductions).

CONCLUSION

Due to the positive effects of ZnO nanoparticle coating on decreasing frictional forces, these nanoparticles might offer a novel opportunity to significantly reduce friction during tooth movement.

No evidence of the genotoxic potential of gold, silver, zinc oxide and titanium dioxide nanoparticles in the SOS chromotest

Gold nanoparticles (Au NPs), silver nanoparticles (Ag NPs), zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO2 NPs) are widely used in cosmetic products such as preservatives, colorants and sunscreens. This study investigated the genotoxicity of Au NPs, Ag NPs, ZnO NPs and TiO2 NPs using the SOS chromotest with Escherichia coli PQ37. The maximum exposure concentrations for each nanoparticle were 3.23 mg l(-1) for Au NPs, 32.3 mg l(-1) for Ag NPs and 100 mg l(-1) for ZnO NPs and TiO2 NPs. Additionally, in order to compare the genotoxicity of nanoparticles and corresponding dissolved ions, the ions were assessed in the same way as nanoparticles. The genotoxicity of the titanium ion was not assessed because of the extremely low solubility of TiO2 NPs. Au NPs, Ag NPs, ZnO NPs, TiO2 NPs and ions of Au, Ag and Zn, in a range of tested concentrations, exerted no effects in the SOS chromotest, evidenced by maximum IF (IFmax) values of below 1.5 for all chemicals. Owing to the results, nanosized Au NPs, Ag NPs, ZnO NPs, TiO2 NPs and ions of Au, Ag and Zn are classified as non-genotoxic on the basis of the SOS chromotest used in this study. To the best of our knowledge, this is the first study to evaluate the genotoxicity of Au NPs, Ag NPs, ZnO NPs and TiO2 NPs using the SOS chromotest.

Effect of different spiking procedures on the distribution and toxicity of ZnO nanoparticles in soil

Due to the difficulty in dispersing some engineered nanomaterials in exposure media, realizing homogeneous distributions of nanoparticles (NP) in soil may pose major challenges. The present study investigated the distribution of zinc oxide (ZnO) NP (30 nm) and non-nano ZnO (200 nm) in natural soil using two different spiking procedures, i.e. as dry powder and as suspension in soil extract. Both spiking procedures showed a good recovery (>85 %) of zinc and based on total zinc concentrations no difference was found between the two spiking methods. Both spiking procedures resulted in a fairly homogeneous distribution of the ZnO particles in soil, as evidenced by the low variation in total zinc concentration between replicate samples (<12 % in most cases). Survival of Folsomia candida in soil spiked at concentrations up to 6,400 mg Zn kg(-1) d.w. was not affected for both compounds. Reproduction was reduced in a concentration-dependent manner with EC50 values of 3,159 and 2,914 mg Zn kg(-1) d.w. for 30 and 200 nm ZnO spiked as dry powder and 3,593 and 5,633 mg Zn kg(-1) d.w. introduced as suspension. Toxicity of ZnO at 30 and 200 nm did not differ. We conclude that the ZnO particle toxicity is not size related and that the spiking of the soil with ZnO as dry powder or as a suspension in soil extract does not affect its toxicity to F. candida.

Optical imaging to trace near infrared fluorescent zinc oxide nanoparticles following oral exposure

Background

Understanding how nanomaterials are distributed in the body after exposure is important for assessing whether they are safe. In this study, we investigated the behavior and accumulation of nanoscaled and submicron-scaled zinc oxide (ZnO) particles in the body using optical imaging following oral exposure.

Methods

To trace these nanoparticles in the body, ZnO nanoparticles were conjugated with a monoreactive hydroxysuccinimide ester of Cy5.5 (Cy5.5-NHS), and the conjugation-stabilizing effect of Cy5.5 on the nanoparticles was evaluated in simulated gastric fluid (pH 1.2) for 7 hours. To compare the distribution of Cy5.5-NHS and Cy5.5-conjugated ZnO nanoparticles, Cy5.5-NHS 0.5 mg/kg and Cy5.5-conjugated ZnO nanoparticles 250 mg/kg were administered orally to healthy rats. We collected blood from the rats at predesignated time points for 7 hours after administration, and optical imaging studies were performed at 1, 2, 3, 5, and 7 hours after dosing. To investigate the extent of nanoparticle accumulation in the organs and tissues, the mice were sacrificed at 23 hours after administration, and the organs were removed and imaged.

Results

Cy5.5-conjugated ZnO nanoparticles were stable in simulated gastric fluid for 7 hours. The signal intensity of Cy5.5-NHS in blood was highest 3 hours after oral administration, and Cy5.5-conjugated ZnO nanoparticles showed the highest signal intensity in blood 5–7 hours after administration. In vivo optical images indicated that Cy5.5-NHS showed optical signals in the lung, liver, and gastrointestinal tract after oral administration, whereas Cy5.5-conjugated ZnO nanoparticles were seen only in the gastrointestinal tract. Seven hours following administration, biodistribution studies demonstrated that Cy5.5-NHS accumulated in the lung and liver, and Cy5.5-conjugated ZnO nanoparticles resulted in a strong signal in the kidney and liver. Different-sized ZnO nanoparticles showed dissimilar patterns of biodistribution in ex vivo optical images.

Conclusion

ZnO nanoparticles are absorbed into the tissues following oral exposure and their behavior can be monitored and evaluated using optical imaging.

Synthesis of zinc oxide nanoparticles and their effect on the compressive strength and setting time of self-compacted concrete paste as cementitious composites

In the present study, the mechanical properties of self-compacting concrete were investigated after the addition of different amounts of ZnO nanoparticles. The zinc oxide nanoparticles, with an average particle size of about 30 nm, were synthesized and their properties studied with the help of a scanning electron microscope (SEM) and X-ray diffraction. The prepared nanoparticles were partially added to self-compacting concrete at different concentrations (0.05, 0.1, 0.2, 0.5 and 1.0%), and the mechanical (flexural and split tensile) strength of the specimens measured after 7, 14, 21 and 28 days, respectively. The present results have shown that the ZnO nanoparticles were able to improve the flexural strength of self-compacting concrete. The increased ZnO content of more than 0.2% could increase the flexural strength, and the maximum flexural and split tensile strength was observed after the addition of 0.5% nanoparticles. Finally, ZnO nanoparticles could improve the pore structure of the self-compacted concrete and shift the distributed pores to harmless and less-harmful pores, while increasing mechanical strength.

Nano-zinc oxide damages spatial cognition capability via over-enhanced long-term potentiation in hippocampus of Wistar rats

This study focused on the effects of zinc oxide nanoparticles (nano-ZnO) on spatial learning and memory and synaptic plasticity in the hippocampus of young rats, and tried to interpret the underlying mechanism. Rats were randomly divided into four groups. Nano-ZnO and phosphate-buffered saline were administered in 4-week-old rats for 8 weeks. Subsequently, performance in Morris water maze (MWM) was determined, and then long-term potentiation (LTP) and depotentiation were measured in the perforant pathway to dentate gyrus (DG) in anesthetized rats. The data showed that, (1) in MWM, the escape latency was prolonged in the nano-ZnO group and, (2) LTP was significantly enhanced in the nano-ZnO group, while depotentiation was barely influenced in the DG region of the nano-ZnO group. This bidirectional effect on long-term synaptic plasticity broke the balance between stability and flexibility of cognition. The spatial learning and memory ability was attenuated by the alteration of synaptic plasticity in nano-ZnO-treated rats.

Zinc oxide nanoparticles as selective killers of proliferating cells

Background:

It has recently been demonstrated that zinc oxide nanoparticles (ZnO NPs) induce death of cancerous cells whilst having no cytotoxic effect on normal cells. However, there are several issues which need to be resolved before translation of zinc oxide nanoparticles into medical use, including lack of suitable biocompatible dispersion protocols and a better understanding being needed of the mechanism of their selective cytotoxic action.

Methods:

Nanoparticle dose affecting cell viability was evaluated in a model of proliferating cells both experimentally and mathematically. The key issue of selective toxicity of ZnO NPs toward proliferating cells was addressed by experiments using a biological model of noncancerous cells, ie, mesenchymal stem cells before and after cell differentiation to the osteogenic lineage.

Results:

In this paper, we report a biocompatible protocol for preparation of stable aqueous solutions of monodispersed zinc oxide nanoparticles. We found that the threshold of intracellular ZnO NP concentration required to induce cell death in proliferating cells is 0.4 ± 0.02 mM. Finally, flow cytometry analysis revealed that the threshold dose of zinc oxide nanoparticles was lethal to proliferating pluripotent mesenchymal stem cells but exhibited negligible cytotoxic effects to osteogenically differentiated mesenchymal stem cells.

Conclusion:

Results confirm the ZnO NP selective cytotoxic action on rapidly proliferating cells, whether benign or malignant.