Fabrication of porous and visible light active ZnO nanorods and ZnO@TiO2 core-shell photocatalysts for self-cleaning applications

Highly transparent and self-cleaning ZnO nanorods (NRs) and ZnO@TiO₂ core-shell (CS) nanoarrays were fabricated using the sol-gel dip-coating technique. TiO₂ nanoparticles (NPs) were coated as a shell layer over the hydrothermally grown ZnO NRs. The number of shell layers on the ZnO NRs was varied by modulating the number of dipping cycles from 1 to 3 to optimize their transmittance. The optimized CS nanoarrays with two dipping cycles display a 2% enhancement of optical transmission compared to the ZnO NRs. In addition, superhydrophilicity (contact angle ∼of 12°) stimulates the self-cleaning nature of the thin films. A water contact angle of 12° was noted for the ZnO@TiO₂: 2 cycle sample, indicating their superhydrophilic nature. Moreover, the photocatalytic activity of the pristine ZnO NRs and ZnO@TiO₂ CS nanoarrays was tested under UV and direct sunlight through the dye degradation of methylene blue (MB). Based upon the TiO₂ morphology and accessibility of the ZnO@TiO₂ heterojunction interface, CS nanoarrays with two shell layers exhibit the highest degree of dye photodegradation efficiency of 68.72% and 91% under sunlight and UV light irradiation, respectively. The CS nanoarrays demonstrate medium sunlight and excellent UV-light-driven photocatalytic activity. Our findings suggest that the ZnO@TiO₂ CS nanoarrays are potential photocatalysts for dye degradation and self-cleaning applications in solar cell coverings.

Recent advances and mechanism of antimicrobial efficacy of graphene-based materials: a review

Graphene-based materials have undergone substantial investigation in recent years owing to their wide array of physicochemical characteristics. Employment of these materials in the current state, where infectious illnesses caused by microbes have severely damaged human life, has found widespread application in combating fatal infectious diseases. These materials interact with the physicochemical characteristics of the microbial cell and alter or damage them. The current review is dedicated to molecular mechanisms underlying the antimicrobial property of graphene-based materials. Various physical and chemical mechanisms leading to cell membrane stress, mechanical wrapping, photo-thermal ablation as well as oxidative stress exerting antimicrobial effect have also been thoroughly discussed. Furthermore, an overview of the interactions of these materials with membrane lipids, proteins, and nucleic acids has been provided. A thorough understanding of discussed mechanisms and interactions is essential to develop extremely effective antimicrobial nanomaterial for application as an antimicrobial agent.

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Composite Coating for the Food Industry Based on Fluoroplast and ZnO-NPs: Physical and Chemical Properties, Antibacterial and Antibiofilm Activity, Cytotoxicity

Bacterial contamination of meat products during its preparation at the enterprise is an important problem for the global food industry. Cutting boards are one of the main sources of infection. In order to solve this problem, the creation of mechanically stable coatings with antibacterial activity is one of the most promising strategies. For such a coating, we developed a composite material based on "liquid" Teflon and zinc oxide nanoparticles (ZnO-NPs). The nanoparticles obtained with laser ablation had a rod-like morphology, an average size of ~60 nm, and a ζ-potential of +30 mV. The polymer composite material was obtained by adding the ZnO-NPs to the polymer matrix at a concentration of 0.001-0.1% using the low-temperature technology developed by the research team. When applying a composite material to a surface with damage, the elimination of defects on a micrometer scale was observed. The effect of the composite material on the generation of reactive oxygen species (H₂O₂, •OH), 8-oxoguanine in DNA in vitro, and long-lived reactive protein species (LRPS) was evaluated. The composite coating increased the generation of all of the studied compounds by 50-200%. The effect depended on the concentration of added ZnO-NPs. The antibacterial and antibiofilm effects of the Teflon/ZnO NP coating against L. monocytogenes, S. aureus, P. aeruginosa, and S. typhimurium, as well as cytotoxicity against the primary culture of mouse fibroblasts, were studied. The conducted microbiological study showed that the fluoroplast/ZnO-NPs coating has a strong bacteriostatic effect against both Gram-positive and Gram-negative bacteria. In addition, the fluoroplast/ZnO-NPs composite material only showed potential cytotoxicity against primary mammalian cell culture at a concentration of 0.1%. Thus, a composite material has been obtained, the use of which may be promising for the creation of antibacterial coatings in the meat processing industry.

Formation of a ZnO nanorods-patterned coating with strong bactericidal capability and quantitative evaluation of the contribution of nanorods-derived puncture and ROS-derived killing

To endow Ti-based orthopedic implants with strong bactericidal activity, a ZnO nanorods-patterned coating (namely ZNR) was fabricated on Ti utilizing a catalyst- and template-free method of micro-arc oxidation (MAO) and hydrothermal treatment (HT). The coating comprises an outer layer of ZnO nanorods and a partially crystallized inner layer with nanocrystalline TiO₂ and Zn₂TiO₄ embedded amorphous matrix containing Ti, O and Zn. During HT, Zn²⁺ ions contained in amorphous matrix of the as-MAOed layer migrate to surface and react with OH⁻ in hydrothermal solution to form ZnO nuclei growing in length at expense of the migrated Zn²⁺. ZNR exhibits intense bactericidal activity against the adhered and planktonic S. aureus in vitro and in vivo. The crucial contributors to kill the adhered bacteria are ZnO nanorods derived mechano-penetration and released reactive oxygen species (ROS). Within 30 min of S. aureus incubation, ROS is the predominant bactericidal contributor with quantitative contribution value of ∼20%, which transforms into mechano-penetration with prolonging time to reach quantitative contribution value of ∼96% at 24 h. In addition, the bactericidal contributor against the planktonic bacteria of ZNR is relied on the released Zn²⁺. This work discloses an in-depth bactericidal mechanism of ZnO nanorods.

(1)

A templates and catalysts-free method is used to fabricate ZnO nanorods on Ti

(2)

ZnO nanorods-arrayed coating shows intense broad-spectrum bactericidal activity

(3)

Main bactericidal contributor of ZnO nanorods to adhered bacteria is mechano-puncture

(4)

Main bactericidal contributor of ZnO nanorods to planktonic bacteria is released Zn²⁺

Prevention of infection caused by enteropathogenic E. coli O157:H7 in intestinal cells using enrofloxacin entrapped in polymer based nanocarriers

Poor bioavailability of antibiotics, toxicity, and development of antibiotic-resistant bacteria jeopardize antibiotic treatments. To circumvent these issues, drug delivery using nanocarriers are highlighted to secure the future of antibiotic treatments. This work investigated application of nanocarriers, to prevent and treat bacterial infection, presenting minimal toxicity to the IPEC-J2 cell line. To accomplish this, polymer-based nanoparticles (NPs) of poly(lactide-co-glycolide) (PLGA) and lignin-graft-PLGA (LNP) loaded with enrofloxacin (ENFLX) were synthesized, yielding spherical particles with average sizes of 111.8 ± 0.6 nm (PLGA) and 117.4 ± 0.9 nm (LNP). The releases of ENFLX from PLGA and LNP were modeled by a theoretical diffusion model considering both the NP and dialysis diffusion barriers for drug release. Biocompatible concentrations of ENFLX, enrofloxacin loaded PLGA(Enflx) and LNP(Enflx) were determined based on examination of bacterial inhibition, toxicity, and ROS generation. Biocompatible concentrations were used for treatment of higher- and lower-level infections in IPEC-J2 cells. Prevention of bacterial infection by LNP(Enflx) was enhanced more than 50% compared to ENFLX at lower-level infection. At higher-level infection, PLGA(Enflx) and LNP(Enflx) demonstrated 25% higher prevention of bacteria growth compared to ENFLX alone. The superior treatment achieved by the nanocarried drug is accredited to particle uptake by endocytosis and slow release of the drug intracellularly, preventing rapid bacterial growth inside the cells.

Antipathogenic properties and applications of low-dimensional materials

A major health concern of the 21st century is the rise of multi-drug resistant pathogenic microbial species. Recent technological advancements have led to considerable opportunities for low-dimensional materials (LDMs) as potential next-generation antimicrobials. LDMs have demonstrated antimicrobial behaviour towards a variety of pathogenic bacterial and fungal cells, due to their unique physicochemical properties. This review provides a critical assessment of current LDMs that have exhibited antimicrobial behaviour and their mechanism of action. Future design considerations and constraints in deploying LDMs for antimicrobial applications are discussed. It is envisioned that this review will guide future design parameters for LDM-based antimicrobial applications.

FeCo nanoparticles as antibacterial agents with improved response in magnetic field: An insight into the associated toxicity mechanism

The emergence of multi-drug resistant bacterial infections has resulted in increased interest in the development of alternative systems which can sensitize bacteria to overcome resistance. In an attempt to contribute to the existing literature of potential antibacterial agents, we present here, a first report of the antibacterial potential of FeCo nanoparticles, both as stand-alone devices and in presence of magnetic field, against the bacterial strains of S. aureus and E. coli. A relatively simple polyol process was employed for nanoparticle synthesis. Formation of FeCo alloy in the desired BCC phase was confirmed by X-Ray Diffraction with a high saturation magnetization (Ms~180 Am2kg-1). Uniformly sized spherical structures with sharp edges were obtained. Solution stability was confirmed by the zeta potential value of -27.8 mV. Dose dependent bacterial growth inhibition was observed, the corresponding linear correlation coefficients being, R2 = 0.74 for S. aureus and R2 = 0.76 for E. coli. Minimum inhibitory concentration was accordingly ascertained to be >1024 μg/ml for both. Bacterial growth curves have been examined upon concomitant application of external magnetic field of varying intensities and revealed considerable enhancement in the antibacterial response upto 63% in a field of 100 mT. An effort has been made to understand the bacterial inhibitory mechanism by relating with the chemical and physical properties of the nanoparticles. The ease of field assisted targeting and retrieval of these highly magnetic, antibacterial nano-devices, with considerably improved response with magnetic fields, make them promising for several medical and environment remediation technologies.

Zinc oxide and zinc oxide-based nanostructures: biogenic and phytogenic synthesis, properties and applications

Zinc oxide nanoparticles (ZnO NPs) are considered as very significant and essential material due to its multifunctional properties, stability, low cost and wide usage. Many green and biogenic approaches for ZnO NPs synthesis have been reported using various sources such as plants and microorganisms. Plants contain biomolecules that can act as capping, oxidizing and reducing agents that increase the rate of reaction and stabilizes the NPs. This review emphasizes and compiles different types of plants and parts of plant used for the synthesis of ZnO and its potential applications at one place. The influence of biogenic and phytogenic synthesized ZnO on its properties and possible mechanisms for its fabrication has been discussed. This review also highlights the potential applications and future prospects of phytogenic synthesized ZnO in the field of energy production and storage, sun light harvesting, environmental remediation, and biological applications.

Core–shell hybrid structured rGO decorated ZnO nanorods synthesized via a facile chemical route with photosensitive properties

Two-dimensional graphene-based nanocomposites have gained much attention due to their promising applications in electronic and optoelectronic devices.

Zinc Complex Derived from ZnCl2-Urea Ionic Liquid for Improving Mildew Property of Bamboo

The nanometer zinc complex, formed in chloride-urea ionic liquid (IL), was studied with the objective of enhancing the mildew resistance of bamboo. The nano-Zinc complex layer was coated on the bamboo surface by a simple and mild heating process. The SEM analysis revealed that the morphology of the nanometer Zinc complex layer on the bamboo surface varied with the reaction time of bamboo in zinc chloride (ZnCl2)/urea ionic liquid. The result of EDS and FTIR analysis showed that zinc and chlorine were successfully coated on the surface of bamboo. In this study, it was found that the optimum condition was 2 h of reaction with 1:2 molar ratio of zinc chloride to urea, where the nano-Zinc complex layer on the bamboo surface was the most uniform and dense to present the bamboo with the strongest mildew resistance. The infection value of Trichoderma viride, Aspergillus niger V. Tiegh, and Penicillium citrinum Thom after 28 day was 0.

A critical review on the applications and potential risks of emerging MoS2 nanomaterials

Molybdenum disulfide (MoS₂) nanomaterials have been widely used in various fields such as energy store and transformation, environment protection, and biomedicine due to their unique physicochemical properties. Unfortunately, such large-scale production and use of MoS₂ nanomaterials would inevitably release into the environmental system and then potentially increase the risks of wildlife/ecosystem and human beings as well. In this review, we first introduce the physicochemichemical properties, synthetic methods and environmental behaviors of MoS₂ nanomaterials and their typical functionalized materials, then summarize their environmental and biomedical applications, next assess their potential health risks, covering in vivo and in vitro studies, along with the underlying toxicological mechanisms, and last point out some special phenomena about the balance between applications and potential risks. This review aims to provide guidance for harm predication induced by MoS₂ nanomaterials and to suggest prevention measures based on the recent research progress of MoS₂' applications and exerting toxicological data.

Application of Nanotechnology in Wood-Based Products Industry: A Review

Wood-based industry is one of the main drivers of economic growth in Malaysia. Forest being the source of various lignocellulosic materials has many untapped potentials that could be exploited to produce sustainable and biodegradable nanosized material that possesses very interesting features for use in wood-based industry itself or across many different application fields. Wood-based products sector could also utilise various readily available nanomaterials to enhance the performance of existing products or to create new value added products from the forest. This review highlights recent developments in nanotechnology application in the wood-based products industry.

Toxicity of Different Zinc Oxide Nanomaterials at 3 Trophic Levels: Implications for Development of Low-Toxicity Antifouling Agents

Because zinc oxide (ZnO) nanomaterials are used in antifouling and antibacterial solutions, understanding their toxic effects on different aquatic organisms is essential. In the present study, we evaluated the toxicity of ZnO nanoparticles of 10 to 30 nm (ZnONPI) and 80 to 200 nm (ZnONPII), ZnO nanorods (width 80 nm, height 1.7 µm) attached to the support substrate (glass, ZnONRG) and not attached (ZnONRS), as well as Zn²⁺ ions at concentrations ranging from 0.5 to 100 mg/L. Toxicity was evaluated using the microalga Dunaliella salina, the brine shrimp Artemia salina, and the marine bacterium Bacillus cereus. The highest toxicity was observed for ZnONPs (median lethal concentration [LC50] ~15 mg/L) and Zn²⁺ ions (LC50 ~13 mg/L), whereas the lowest toxicity found for ZnO nanorods (ZnONRG LC50 ~60 mg/L; ZnONRS LC50 ~42 mg/L). The presence of the support substrate in case of ZnO nanorods reduced the associated toxicity to aquatic organisms. Smaller ZnONPs resulted in the highest Zn²⁺ ion dissolution among tested nanostructures. Different aquatic organisms responded differently to ZnO nanomaterials, with D. salina and B. cereus being more sensitive than A. salina. Toxicity of nanostructures increased with an increase of the dose and the time of exposure. Supported ZnO nanorods can be used as a low-toxicity alternative for future antimicrobial and antifouling applications. Environ Toxicol Chem 2020;39:1343-1354. © 2020 SETAC.

On the Interaction between 1D Materials and Living Cells

One-dimensional (1D) materials allow for cutting-edge applications in biology, such as single-cell bioelectronics investigations, stimulation of the cellular membrane or the cytosol, cellular capture, tissue regeneration, antibacterial action, traction force investigation, and cellular lysis among others. The extraordinary development of this research field in the last ten years has been promoted by the possibility to engineer new classes of biointerfaces that integrate 1D materials as tools to trigger reconfigurable stimuli/probes at the sub-cellular resolution, mimicking the in vivo protein fibres organization of the extracellular matrix. After a brief overview of the theoretical models relevant for a quantitative description of the 1D material/cell interface, this work offers an unprecedented review of 1D nano- and microscale materials (inorganic, organic, biomolecular) explored so far in this vibrant research field, highlighting their emerging biological applications. The correlation between each 1D material chemistry and the resulting biological response is investigated, allowing to emphasize the advantages and the issues that each class presents. Finally, current challenges and future perspectives are discussed.

Enhanced Anti-Mold Property and Mechanism Description of Ag/TiO2 Wood-Based Nanocomposites Formation by Ultrasound- and Vacuum-Impregnation

Ag/TiO₂ wood-based nanocomposites were prepared by the methods of ultrasound impregnation and vacuum impregnation. The as-prepared samples were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), mercury intrusion porosimetry (MIP), and water contact angles (WCAs). The anti-mold properties of the Ag/TiO₂ wood-based nanocomposites were improved by 14 times compared to those of the original wood. The nano-Ag/TiO₂, which was impregnated in the tracheid and attached to the cell walls, was able to form a two-stage rough structure and reduce the number of hydroxyl functional groups on the wood surfaces. The resulting decline of wood hydrophobic and equilibrium moisture content (EMC) destroyed the moisture environment necessary for mold survival. Ag/TiO₂ was deposited in the wood pores, which reduced the number and volume of pores and blocked the path of mold infection. Thus, the anti-mold properties of the Ag/TiO₂ wood-based nanocomposite were improved by cutting off the water source and blocking the mold infection path. This study reveals the anti-mold mechanism of Ag/TiO₂ wood-based nanocomposites and provides a feasible pathway for wood-based nanocomposites with anti-mold functions.

Progress on particulate matter filtration technology: basic concepts, advanced materials, and performances

The PM (particulate matter)-induced haze problem has caused serious environmental and health concerns. It is still a huge challenge to control PM pollution because of the complex structure, diverse sources and intricate evolution mechanism of the particles. In recent years, there has been increasing efforts to develop advanced strategies for PM treatment. Herein, we wish to provide a systematic summary of recent progress in air filtration. The review covers the definition of PM, the characterization of PM, the mechanism of PM capture, advanced purification materials, and special multifunctional performances. As for characterizing PM particles, removal efficiency, pressure drop, flow rate, quality factor and optical transparency are the basic parameters. For the advanced filters with excellent filtration performance, some special properties such as thermal stability, antibacterial property, flame retardancy, recyclability and special wettability are in great need under certain extreme conditions. Finally, some future prospects for filtration materials, like material choice and structural design, are also discussed.

Organic–inorganic bimetallic hybrid particles with controllable morphology for the catalytic degradation of organic dyes

Amphiphilic bimetallic hybrid Janus nanoparticles with controllable morphology and ability to perform highly efficient catalytic degradation of organic dyes.

ZnO Nanostructures and Electrospun ZnO-Polymeric Hybrid Nanomaterials in Biomedical, Health, and Sustainability Applications

ZnO-based nanomaterials are a subject of increasing interest within current research, because of their multifunctional properties, such as piezoelectricity, semi-conductivity, ultraviolet absorption, optical transparency, and photoluminescence, as well as their low toxicity, biodegradability, low cost, and versatility in achieving diverse shapes. Among the numerous fields of application, the use of nanostructured ZnO is increasingly widespread also in the biomedical and healthcare sectors, thanks to its antiseptic and antibacterial properties, role as a promoter in tissue regeneration, selectivity for specific cell lines, and drug delivery function, as well as its electrochemical and optical properties, which make it a good candidate for biomedical applications. Because of its growing use, understanding the toxicity of ZnO nanomaterials and their interaction with biological systems is crucial for manufacturing relevant engineering materials. In the last few years, ZnO nanostructures were also used to functionalize polymer matrices to produce hybrid composite materials with new properties. Among the numerous manufacturing methods, electrospinning is becoming a mainstream technique for the production of scaffolds and mats made of polymeric and metal-oxide nanofibers. In this review, we focus on toxicological aspects and recent developments in the use of ZnO-based nanomaterials for biomedical, healthcare, and sustainability applications, either alone or loaded inside polymeric matrices to make electrospun composite nanomaterials. Bibliographic data were compared and analyzed with the aim of giving homogeneity to the results and highlighting reference trends useful for obtaining a fresh perspective about the toxicity of ZnO nanostructures and their underlying mechanisms for the materials and engineering community.

Facile Fabrication of Multifunctional ZnO Urchins on Surfaces

Functional ZnO nanostructured surfaces are important in a wide range of applications. Here we report the simple fabrication of ZnO surface structures at near room temperature with morphology resembling that of sea urchins, with densely packed, μm-long, tapered nanoneedles radiating from the urchin center. The ZnO urchin structures were successfully formed on several different substrates with high surface density and coverage, including silicon (Si), glass, polydimethylsiloxane (PDMS), and copper (Cu) sheets, as well as Si seeded with ZnO nanocrystals. Time-resolved SEM revealed growth kinetics of the ZnO nanostructures on Si, capturing the emergence of “infant” urchins at the early growth stage and subsequent progressive increases in the urchin nanoneedle length and density, whilst the spiky nanoneedle morphology was retained throughout the growth. ε-Zn(OH)2 orthorhombic crystals were also observed alongside the urchins. The crystal structures of the nanostructures at different growth times were confirmed by synchrotron X-ray diffraction measurements. On seeded Si substrates, a two-stage growth mechanism was identified, with a primary growth step of vertically aligned ZnO nanoneedle arrays preceding the secondary growth of the urchins atop the nanoneedle array. The antibacterial, anti-reflective, and wetting functionality of the ZnO urchins—with spiky nanoneedles and at high surface density—on Si substrates was demonstrated. First, bacteria colonization was found to be suppressed on the surface after 24 h incubation in gram-negative Escherichia coli (E. coli) culture, in contrast to control substrates (bare Si and Si sputtered with a 20 nm ZnO thin film). Secondly, the ZnO urchin surface, exhibiting superhydrophilic property with a water contact angle ~ 0°, could be rendered superhydrophobic with a simple silanization step, characterized by an apparent water contact angle θ of 159° ± 1.4° and contact angle hysteresis ∆θ < 7°. The dynamic superhydrophobicity of the surface was demonstrated by the bouncing-off of a falling 10 μL water droplet, with a contact time of 15.3 milliseconds (ms), captured using a high-speed camera. Thirdly, it was shown that the presence of dense spiky ZnO nanoneedles and urchins on the seeded Si substrate exhibited a reflectance R < 1% over the wavelength range λ = 200–800 nm. The ZnO urchins with a unique morphology fabricated via a simple route at room temperature, and readily implementable on different substrates, may be further exploited for multifunctional surfaces and product formulations.

Enhancement of local surface plasmon resonance (LSPR) effect by biocompatible metal clustering based on ZnO nanorods in Raman measurements

The development of size-selective and non-destructive detection techniques for nanosized biomarkers has many reasons, including the study of living cells and diagnostic applications. We present an approach for Raman signal enhancement on biocompatible sensing chips based on surface enhancement Raman spectroscopy (SERS). A sensing chip was fabricated by forming a ZnO-based nanorod structure so that the Raman enhancement occurred at a gap of several tens to several hundred nanometers. The effect of coffee-ring formation was eliminated by introducing the porous ZnO nanorods for the bio-liquid sample. A peculiarity of this approach is that the gold sputtered on the ZnO nanorods initially grows at their heads forming clusters, as confirmed by secondary electron microscopy. This clustering was verified by finite element analysis to be the main factor for enhancement of local surface plasmon resonance (LSPR). This clustering property and the ability to adjust the size of the nanorods enabled the signal acquisition points to be refined using confocal based Raman spectroscopy, which could be applied directly to the sensor chip based on the optimization process in this experiment. It was demonstrated by using common cancer cell lines that cell growth was high on these gold-clad ZnO nanorod-based surface-enhanced Raman substrates. The porosity of the sensing chip, the improved structure for signal enhancement, and the cell assay make these gold-coated ZnO nanorods substrates promising biosensing chips with excellent potential for detecting nanometric biomarkers secreted by cells.

Noble metal-coated MoS2 nanofilms with vertically-aligned 2D layers for visible light-driven photocatalytic degradation of emerging water contaminants

Two-dimensional molybdenum disulfide (2D MoS2) presents extraordinary optical, electrical, and chemical properties which are highly tunable by engineering the orientation of constituent 2D layers. 2D MoS2 films with vertically-aligned layers exhibit numerous 2D edge sites which are predicted to offer superior chemical reactivity owing to their enriched dangling bonds. This enhanced chemical reactivity coupled with their tunable band gap energy can render the vertical 2D MoS2 unique opportunities for environmental applications that go beyond the conventional applications of horizontal 2D MoS2 in electronics/opto-electronics. Herein, we report that MoS2 films with vertically-aligned 2D layers exhibit excellent visible light responsive photocatalytic activities for efficiently degrading organic compounds in contaminated water such as harmful algal blooms. We demonstrate the visible light-driven rapid degradation of microcystin-LR, one of the most toxic compounds produced by the algal blooms, and reveal that the degradation efficiency can be significantly improved by incorporating noble metals. This study suggests a high promise of these emerging 2D materials for water treatment, significantly broadening their versatility for a wide range of energy and environmental applications.

Cell mechanotactic and cytotoxic response to zinc oxide nanorods depends on substrate stiffness

Bio-nanomaterials offer promise in the field of tissue engineering. Specifically, environmental cues such as the material chemistry, topography and rigidity of the surface to which cells adhere to, can alter and dictate cell shape, proliferation, migration, and gene expression. How deeply each factor (topographical, chemical and mechanical) drives cell response remains incompletely understood. To illustrate cell sensitivities to different factors, we herein present ZnO nanorods (ZnO-Nrds) coated on glass and polydimethylsiloxane (PDMS) substrates and analyzed cell viability and proliferation. The work presented here shows a clear response of various cell lines (mouse embryonic fibroblasts 3T3, human cervix carcinoma HeLa and human osteoblast-like cells MG63) to the rigidity of the underlying surface. The chemical counterpart, given by the presence of ZnO-Nrds, strongly reduced the cell viability of all cell lines. However, the substrate underlying the ZnO coating impacted cell spreading and viability. The substrates exhibited a better ability to neglect cell attachment and proliferation with the ZnO coating and pro-apoptoticity specifically with the PDMS as the underlying substrate which exhibited a "softer" environment with respect to a glass substrate. The results also revealed that the few cells that adhered to the ZnO-Nrds on PDMS and glass showed a rounded morphology. On the basis of these observations, we can correlate common features of phenomenological cell response to chemotactic and durotactic cues. The work presented herein reinforces the response of cells to changes in substrate rigidity. These observations provide a foundation for a potentially promising approach to decrease cell adhesion and thus as an optimal substrate for different applications such as prosthesis design, tissue engineering, anti-bio fouling materials and diagnostics.

Effect of pulmonary surfactant on the dissolution, stability and uptake of zinc oxide nanowires by human respiratory epithelial cells

Inhaled nanoparticles (NPs) have high-deposition rates in the alveolar region of the lung but the effects of pulmonary surfactant (PS) on nanoparticle bioreactivity are unclear. Here, the impact of PS on the stability and dissolution of ZnO nanowires (ZnONWs) was investigated, and linked with their bioreactivity in vitro with human alveolar epithelial type 1-like cells (TT1). Pre-incubation of ZnONWs with Curosurf® (a natural porcine PS) decreased their dissolution at acidic pH, through the formation of a phospholipid corona. Confocal live cell microscopy confirmed that Curosurf® lowered intracellular dissolution, thus delaying the onset of cell death compared to bare ZnONWs. Despite reducing dissolution, Curosurf® significantly increased the uptake of ZnONWs within TT1 cells, ultimately increasing their toxicity after 24 h. Although serum improved ZnONW dispersion in suspension similar to Curosurf®, it had no effect on ZnONW internalization and toxicity, indicating a unique role of PS in promoting particle uptake. In the absence of PS, ZnONW length had no effect on dissolution kinetics or degree of cellular toxicity, indicating a less important role of length in determining ZnONW bioreactivity. This work provides unique findings on the effects of PS on the stability and toxicity of ZnONWs, which could be important in the study of pulmonary toxicity and epithelial-endothelial translocation of nanoparticles in general.

Control of the size and density of ZnO-nanorods grown onto graphene nanoplatelets in aqueous suspensions

Zinc oxide nanorods with controlled density and size and high chemical purity were grown onto unsupported graphene nanoplatelets in aqueous suspension.

Unusual Air Filters with Ultrahigh Efficiency and Antibacterial Functionality Enabled by ZnO Nanorods

Porous membranes/filters that can remove airborne fine particulates, for example, PM2.5, with high efficiency at low energy consumption are of significant interest. Herein, we report on the fabrication of a new class of unusual superior air filters with ultrahigh efficiency and an interesting antibacterial functionality. We use atomic layer deposition (ALD) to uniformly seed ZnO on the surface of expanded polytetrafluoroethylene (ePTFE) matrix, and then synthesize well-aligned ZnO nanorods with tunable widths and lengths from the seeds under hydrothermal conditions. The presence of ZnO nanorods reduces the effective pore sizes of the ePTFE filters at little expense of energy consumption. As a consequence, the filters exhibit exceptional dust removal efficiencies greater than 99.9999% with much lower energy consumption than conventional filters. Significantly, the presence of ZnO nanorods strongly inhibits the propagation of both Gram positive and negative bacteria on the filters. Therefore, the functionalized filters can potentially overcome the inherent limitation in the trade-off effect and imply their superiority for controlling indoor air quality.

Mechanistic lessons learned from studies of planktonic bacteria with metallic nanomaterials: implications for interactions between nanomaterials and biofilm bacteria

Metal and metal-oxide nanoparticles (NPs) are used in numerous applications and have high likelihood of entering engineered and natural environmental systems. Careful assessment of the interaction of these NPs with bacteria, particularly biofilm bacteria, is necessary. This perspective discusses mechanisms of NP interaction with bacteria and identifies challenges in understanding NP-biofilm interaction, considering fundamental material attributes and inherent complexities of biofilm structure. The current literature is reviewed, both for planktonic bacteria and biofilms; future challenges and complexities are identified, both in light of the literature and a dataset on the toxicity of silver NPs toward planktonic and biofilm bacteria. This perspective aims to highlight the complexities in such studies and emphasizes the need for systematic evaluation of NP-biofilm interaction.

Enhanced antibacterial activity of Cr doped ZnO nanorods synthesized using microwave processing

Light induced generation of reactive oxygen species from ZnO and Cr:ZnO nanoparticles.

Raspberry-like morphology of polyvinyl chloride/zinc oxide nanoparticles induced by surface interaction and formation of nanoporous foam

P(VC-co-AAEM)/ZnO nanoparticles are prepared by a nano-coating method, and the morphology of the raspberry-like particles is adjusted by hydrophilicity and NaOH concentration.