Alteration of Hordeum vulgare and Sinapis alba germination and early growth in response to airborne low-metallic automotive brake wear debris

Road transportation significantly contributes to environmental pollution, both in terms of exhaust and non-exhaust (brake wear) emissions. As was proven, brake wear debris is released in a wide variety of sizes, shapes, and compositions. Although studies confirming the possible adverse health and environmental impact of brake wear debris were published, there is no standardized methodology for their toxicity testing, and most studies focus only on one type of brake pad and/or one test. The lack of methodology is also related to the very small amount of material released during the laboratory testing. For these reasons, this study deals with the mixture of airborne brake wear debris from several commonly used low-metallic brake pads collected following the dynamometer testing. The mixture was chosen for better simulation of the actual state in the environment and to collect a sufficient amount of particles for thorough characterization (SEM, XRPD, XRF, chromatography, and particle size distribution) and phytotoxicity testing. The particle size distribution measurement revealed a wide range of particle sizes from nanometers to hundreds of nanometers, elemental and phase analysis determined the standard elements and compounds used in the brake pad formulation. The Hordeum vulgare and Sinapis alba were chosen as representatives of monocotyledonous and dicotyledonous plants. The germination was not significantly affected by the suspension of brake wear debris; however, the root elongation was negatively influenced in both cases. Sinapis alba (IC50 = 23.13 g L-1) was more affected than Hordeum vulgare (IC50 was not found in the studied concentration range) the growth of which was even slightly stimulated in the lowest concentrations of brake wear debris. The plant biomass was also negatively affected in the case of Sinapis alba, where the IC50 values of wet and dry roots were determined to be 44.83 g L-1 and 86.86 g L-1, respectively.

Effects of Foliar Application of ZnO Nanoparticles on Lentil Production, Stress Level and Nutritional Seed Quality under Field Conditions

Nanotechnology offers new opportunities for the development of novel materials and strategies that improve technology and industry. This applies especially to agriculture, and our previous field studies have indicated that zinc oxide nanoparticles provide promising nano-fertilizer dispersion in sustainable agriculture. However, little is known about the precise ZnO-NP effects on legumes. Herein, 1 mg·L−1 ZnO-NP spray was dispersed on lentil plants to establish the direct NP effects on lentil production, seed nutritional quality, and stress response under field conditions. Although ZnO-NP exposure positively affected yield, thousand-seed weight and the number of pods per plant, there was no statistically significant difference in nutrient and anti-nutrient content in treated and untreated plant seeds. In contrast, the lentil water stress level was affected, and the stress response resulted in statistically significant changes in stomatal conductance, crop water stress index, and plant temperature. Foliar application of low ZnO-NP concentrations therefore proved promising in increasing crop production under field conditions, and this confirms ZnO-NP use as a viable strategy for sustainable agriculture.

Development of Novel Thin Polycaprolactone (PCL)/Clay Nanocomposite Films with Antimicrobial Activity Promoted by the Study of Mechanical, Thermal, and Surface Properties

Infection with pathogenic microorganisms is of great concern in many areas, especially in healthcare, but also in food packaging and storage, or in water purification systems. Antimicrobial polymer nanocomposites have gained great popularity in these areas. Therefore, this study focused on new approaches to develop thin antimicrobial films based on biodegradable polycaprolactone (PCL) with clay mineral natural vermiculite as a carrier for antimicrobial compounds, where the active organic antimicrobial component is antifungal ciclopirox olamine (CPX). For possible synergistic effects, a sample in combination with the inorganic antimicrobial active ingredient zinc oxide was also prepared. The structures of all the prepared samples were studied by X-ray diffraction, FTIR analysis and, predominantly, by SEM. The very different structure properties of the prepared nanofillers had a fundamental influence on the final structural arrangement of thin PCL nanocomposite films as well as on their mechanical, thermal, and surface properties. As sample PCL/ZnOVER_CPX possessed the best results for antimicrobial activity against examined microbial strains, the synergic effect of CPX and ZnO combination on antimicrobial activity was proved, but on the other hand, its mechanical resistance was the lowest.

Polyamide 12 Materials Study of Morpho-Structural Changes during Laser Sintering of 3D Printing

The polyamide (PA)-12 material used for additive manufacturing was studied in aspects of morphology and their structural properties for basic stages received during 3D laser printing. Samples were real, big-scale production powders. The structure of polymer was evaluated from the crystallinity point of view using XRD, FTIR, and DSC methods and from the surface properties using specific surface evaluation and porosity. Scanning electron microscopy was used to observe morphology of the surface and evaluate the particle size and shape via image analysis. Results were confronted with laser diffraction particles size measurement along with an evaluation of the specific surface area. Fresh PA12 powder was found as inhomogeneous in particle size of material with defective particles, relatively high specific surface, high lamellar crystallite size, and low crystallinity. The scrap PA12 crystallinity was about 2% higher than values for fresh PA12 powder. Particles had a very low, below 1 m²/g, specific surface area; particles sintered as twin particles and often in polyhedral shapes.

Tribo-Mechanical Properties of the Antimicrobial Low-Density Polyethylene (LDPE) Nanocomposite with Hybrid ZnO–Vermiculite–Chlorhexidine Nanofillers

Materials made from low-density polyethylene (LDPE) in the form of packages or catheters are currently commonly applied medical devices. Antimicrobial LDPE nanocomposite materials with two types of nanofillers, zinc oxide/vermiculite (ZnO/V) and zinc oxide/vermiculite_chlorhexidine (ZnO/V_CH), were prepared by a melt-compounded procedure to enrich their controllable antimicrobial, microstructural, topographical and tribo-mechanical properties. X-ray diffraction (XRD) analysis and Fourier transform infrared spectroscopy (FTIR) revealed that the ZnO/V and ZnO/V_CH nanofillers and LDPE interacted well with each other. The influence of the nanofiller concentrations on the LDPE nanocomposite surface changes was studied through scanning electron microscopy (SEM), and the surface topology and roughness were studied using atomic force microscopy (AFM). The effect of the ZnO/V nanofiller on the increase in indentation hardness (HIT) was evaluated by AFM measurements and the Vickers microhardness (HV), which showed that as the concentration of the ZnO/V nanofiller increased, these values decreased. The ZnO/V and ZnO/V_CH nanofillers, regardless of the concentration in the LDPE matrix, slightly increased the average values of the friction coefficient (COF). The abrasion depths of the wear indicated that the LDPE_ZnO/V nanocomposite plates exhibited better wear resistance than LDPE_ZnO/V_CH. Higher HV and HIT microhardness values were measured for both nanofillers than the natural LDPE nanocomposite plate. Very positive antimicrobial activity against S. aureus and P. aeruginosa after 72 h was found for both nanofiller types.

Phytosynthesis of Ag, ZnO and ZrO₂ Nanoparticles Using Linden: Changes in Their Physical-Chemical Nature Over Time

Bionanotechnology provides many new methods and protocols in nanomaterial preparation. One of these special new chemical methods is phytosynthesis. The application of biological processes in living organisms such as bacteria, fungi and higher plants contributes to rapid and easy formation of metallic nanoparticles. These nanoparticles present a promising future in heterogeneous catalysis and medicine, and here we focus on phytosynthesis of Ag, ZnO and ZrO₂ nanoparticles using leachate from the linden plant. Nanoparticle activity in liquid is an important aspect of their behavior, and we investigated nanoparticles ζ-potential and monitored their particle size by dynamic light scattering during the period of three months. Transmission electron microscopy then determined shape and morphology, with results confirming their spherical shape and average size in tens and hundreds of nanometers. The amount of metals was estimated in tens of mg L^-1 and the different nanoparticle sizes obtained by dynamic light scattering and transmission electron microscopy are discussed. The nanoparticles were tested against 4 human pathogens using minimum inhibitory concentration to investigate their antimicrobial potential. Only Ag nanoparticles provided antibacterial properties against Escherichia coli and Pseudomonas aeruginosa; with the remaining nanoparticles having no antibacterial effect on the four tested pathogens. All studied phenomena are related to nanoparticle concentration and their surface charge, and therefore ζ-potential and other physical and chemical properties are important in ascertaining positive and negative aspects of metallic nanoparticles in future applications and related research.

Determination of Oxidative Potential Caused by Brake Wear Debris in Non-Cellular Systems

Wear debris from automotive brake systems represents a major source of non-exhaust emissions from road traffic and its production increases with number of cars worldwide. However, impact of brake wear debris on the environment and organisms is still not clear. One of the most possible ways by which these particles may affect living organisms is oxidative stress. Production of reactive oxidative species may cause damage of basic cell components, lipids, proteins, etc. Aim of this study is to perform characterization of airborne and nonairborne fractions of brake wear debris generated during standard dynamometer tests and evaluation of its potential to induce oxidative stress via lipid peroxidation and carbonylation of proteins in non-cellular system. Elemental and phase composition were determined by scanning electron microscopy, Raman microspectroscopy, and X-ray powder diffraction analysis. Carbon in amorphous form and graphite, copper, and iron in form of oxides were identified as major components in both studied fractions. Characteristic size of studied wear particles was evaluated by dynamic light scattering. Both airborne and nonairborne samples showed ability to induce oxidative stress which results from determination of carbonylated proteins.

Synthesis and Antimicrobial Activity of Polyethylene/Chlorhexidine/Vermiculite Nanocomposites

The set of polyethylene/clay nanocomposites with increasing amount of antimicrobial nanofiller (3, 6 and 10 wt%) was prepared by melt compounding procedure. The antimicrobial drug chlorhexidine diacetate was loaded into natural clay mineral vermiculite and also to its monoionic sodium form and then these organoclay nanofillers were incorporated into polymeric matrix. The structure of prepared organoclays and nanocomposites was studied by X-ray diffraction analysis and Fourier transforms infrared spectroscopy. Further thermal properties of polyethylene/clay nanocomposites were investigated by thermogravimetric analysis and the surface roughness was evaluated by atomic force microscopy. Finally, organoclays and polyethylene/clay nanocomposites were tested for antimicrobial activity against bacterial strains Staphylococcus aureus, Escherichia coli and yeast Candida albicans. Prepared samples showed a very good antimicrobial activity with long lasting effect. In the case of polyethylene/clay nanocomposites we observed some differences in antimicrobial action between two used antimicrobial nanofillers. These results suggested great potential of using the polymer/clay nanocomposites in the wide range of antimicrobial applications.

Microstructure and Electrochemical Behavior of TiO₂ Nanotubes Coated on Titanium-Based Substrate Before and After Thermal Treatment

The comparative study of the structure and electrochemical properties of TiO₂ layers on the surfaces of commercially pure titanium and Ti6Al4V alloy were performed. The TiO₂ surface layers produced by anodization in ethylene glycol-based electrolyte solution using Power Supply MCS-3204 MANSON at 20 V or 40 V for 60 minutes were formed on the titanium substrates by simultaneous surface oxidation and controlled dissolving of oxide film due the fluorine ions. The SEM and X-ray diffraction analyses were performed to determine the properties of the anodized layers before and after heat treatment at 500 °C for 120 minutes. The as-anodized TiO₂ nanotubes exhibited an amorphous structure. An anatase phase appeared in annealed nanotube layers of both Ti based substrates. The corrosion behavior in simulated physiological solution was compared for not anodized, anodized and anodized heat treated conditions of both titanium surfaces. The results of the electrochemical measurements corresponded to the microstructure and treatment condition. The porous feature of the anodizing layers on Ti6Al4V substrate led to lower corrosion resistance that increased after the heat treatment.

Micronization of Ibuprofen Particles Using Supercritical Fluid Technology

Most of drugs are only slightly soluble in the circulatory system of the human body. This reduces the efficiency of their use and that is why new ways how to increase their solubility are investigated. One way to improve the solubility of the drug is to reduce its particle size. Conventional techniques such as crushing or grinding usually do not guarantee a narrow particle size distribution, which is required for pharmaceuticals. Application of supercritical fluids, especially of supercritical CO₂, seems to be convenient method for the preparation of pharmaceuticals submicron particles or nanoparticles. The method enables the preparation of particles in a narrow size distribution and at the same time it does not leave any unwanted residues of solvents or other chemicals. The aim of this work is the micronization of ibuprofen particles using the supercritical fluid and characterization of formed products. The micronization of the particles was done using commercially available device Spe-ed SFE-4 in rapid expansion of supercritical solution mode. The applied temperatures and pressures were 308.15 K and 313.15 K and 200, 250 and 300 bar. The prepared particles were characterized using methods of X-ray diffraction, infrared spectroscopy, particle size distribution, scanning electron microscopy and tests of dissolution and permeability. Mean particles size was reduced from 180 μm (original ibuprofen) to 2.8-7.3 μm of the processed samples. The dissolution test confirmed better solubility and the permeability of newly formed particles improved.

Toxicity of the Zinc Oxide and Vermiculite/Zinc Oxide Nanomaterials

Nanomaterials and nanocomposite materials on the base of zinc oxide (ZnO) are being produced and applied in our daily life at a rapid pace mainly as additives to the different polymer materials. The antibacterial behaviors of ZnO nanoparticles are intensively studied but related health and environmental toxicity assessments are lagging behind. The aim of this work was evaluated the toxic effect of self-synthesized samples (ZnO nanoparticles, vermiculite/ZnO nanocomposite) and one commercial sample of the ZnO nanoparticles, to induce oxidative stress via lipid peroxidation. This ability is one of the indicators of material toxicity. The toxicity results were compared with the results of titanium dioxide nanoparticles as a validated toxic standard. The effect of the major nanoparticles properties as particle and crystallite size, shape, specific phase and composition were evaluated using the dynamic laser diffraction, scanning electron microscopy and X-ray diffraction analysis. The attention was also focused on the influence of the vermiculite (as matrix of nanocomposite samples) and temperature of the nanostructured materials preparation. All samples containing vermiculite are not able to induce peroxidation of lipids in comparison to TiO₂ nanoparticles. However, samples of ZnO nanoparticles demonstrate the ability to induce oxidative stress via lipid peroxidation, which decreases with the increasing temperature of preparation and for commercial ZnO was higher than for prepared ZnO nanoparticles.

Investigation of Geometric Properties of Modified Titanium White by Fluidisation for Use in the Process of Transport, Handling, Processing and Storage

The present article deals with investigation of geometric properties of surface modified titanium white with the help of silica oxide by various methods of shape and size identification of clusters made by processing by fluidisation. For the purpose of the investigation of geometric properties the artificially made titanium oxide (titanium white) was processed by fluidisation with a defined percentage of silica oxide additive. The selected additive was represented by hydrophilic pyrogenic silica (micronised silica oxide), known under commercial name Aerosil 200, Aerosil R972 and hydrophilic pyrogenic metal oxide Aeroxide P25. The investigation began by image acquisition of the individual additives and the titanium white with scanning electron microscope and continued by investigation of clusters created by fluidisation in a vertical fluidisation cell using state-of-the-art methods of particle size identification analysis. The research was oriented toward the area of mutual impact of particles in the titanium white clusters with particles of additives.

Hybrid Antibacterial Nanocomposites Based on the Vermiculite/Zinc Oxide-Chlorhexidine

The hybrid nanocomposite materials based on the vermiculite/zinc oxide-chlorhexidine were prepared in two steps. In the first step the vermiculite/zinc oxide nanocomposite was prepared by the mechanochemical method followed by a heat treatment at 650 °C for 90 min. In the second step the chlorhexidine dihydrochloride was intercalated to the vermiculite/zinc oxide nanocomposite in weight ratio 1:1, 1:2, 1:4, 2:1 and 4:1 (wt%) thereby vermiculite/zinc oxide-chlorhexidine nanocomposites were prepared. Phase analysis, crystal structure, phase transformation, chemical composition and particle size of the prepared hybrid nanocomposite materials were using X-ray diffraction methods, energy dispersive X-ray fluorescence spectroscopy, carbon phase analysis, Fourier transforms infrared spectroscopy and particle size analysis. Antibacterial activity of hybrid nanocomposite materials was investigated on Gram negative (E. coli, P. aeruginos.) and the Gram positive (S. aureus, E. faecalis) bacterial strain and against yeast Candida a. by finding the minimum inhibitory concentration. The hybrid nanocomposite materials exhibit high antibacterial activity after 30 minutes with a long-lasting effect persisting up to 5 days. Dependence of the zinc oxide and chlorhexidine concentration in vermiculite structure on the antibacterial activity was observed.