Effects of ultrasound on zinc oxide/vermiculite/chlorhexidine nanocomposite preparation and their antibacterial activity

Microbial infection and biofilm formation are both problems associated with medical implants and devices. In recent years, hybrid organic-inorganic nanocomposites based on clay minerals have attracted significant attention due to their application potential in the field of antimicrobial materials. Organic drug/metal oxide hybrids exhibit improved antimicrobial activity, and intercalating the above materials into the interlayer of clay endows a long-term and controlled-release behavior. Since antimicrobial activity is strongly related to the structure of the material, ultrasonic treatment appears to be a suitable method for the synthesis of these materials as it can well control particle size distribution and morphology. This study aims to prepare novel, structurally stable, and highly antimicrobial nanocomposites based on zinc oxide/vermiculite/chlorhexidine. The influence of ultrasonic treatment at different time intervals and under different intercalation conditions (ultrasonic action in a breaker or in a Roset's vessel) on the structure, morphology, and particle size of prepared hybrid nanocomposite materials was evaluated by the following methods: scanning electron microscopy, X-ray diffraction, energy dispersive X-ray fluorescence spectroscopy, carbon phase analysis, Fourier transforms infrared spectroscopy, specific surface area measurement, particle size analysis, and Zeta potential analysis. Particle size analyses confirmed that the ultrasonic method contributes to the reduction of particle size, and to their homogenization/arrangement. Further, X-ray diffraction analysis confirmed that ultrasound intercalation in a beaker helps to more efficiently intercalate chlorhexidine dihydrochloride (CH) into the vermiculite interlayer space, while a Roset's vessel contributed to the attachment of the CH molecules to the vermiculite surface. The antibacterial activity of hybrid nanocomposite materials was investigated on Gram negative (Escherichia coli, Pseudomonas aeruginosa) and Gram positive (Staphylococcus aureus, Enterococcus faecalis) bacterial strains by finding the minimum inhibitory concentration. All hybrid nanocomposite materials prepared by ultrasound methods showed high antimicrobial activity after 30 min, with a long-lasting effect and without being affected by the concentration of the antibacterial components zinc oxide (ZnO) and CH. The benefits of the samples prepared by ultrasonic methods are the rapid onset of an antimicrobial effect and its long-term duration.Web of Science99art. no. 130

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. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.[SP2020/08

Hybrid nanofillers creating the stable PVDF nanocomposite films and their effect on the friction and mechanical properties

The solvent casting method was used for five types of polyvinylidene difluoride (PVDF) nanocomposite film preparation. The effect of nanofillers in PVDF nanocomposite films on the structural, phase, and friction and mechanical properties was examined and compared with that of the natural PVDF film. The surface topography of PVDF nanocomposite films was investigated using a scanning electron microscope (SEM) and correlative imaging (CPEM, combinate AFM and SEM). A selection of 2D CPEM images was used for a detailed study of the spherulitic morphologies (grains size around 6-10 mu m) and surface roughness (value of 50-68 nm). The chemical interactions were evaluated by Fourier transform infrared spectroscopy (FTIR). Dominant polar gamma-phase in the original PVDF, PVDF ZnO and PVDF ZnO/V, the most stable non-polar alpha-phase in the PVDF V CH nanocomposite film and mixture of y and oc phases in the PVDF _V and PVDF ZnO/V CH nanocomposite films were confirmed. Moderately hydrophilic PVDF nanocomposite films with water contact angle values (WCA) in the range of 58 degrees-69 degrees showed surface stability with respect to the Zeta potential values. The effect of positive or negative Zeta-potential values of nanofillers (zeta(n)) on the resulting negative Zeta-potential values (zeta) of PVDF nanocomposite films was demonstrated. Interaction of PVDF chains with hydroxy groups of vermiculite and amino and imino groups of CH caused transformation of y-phase to a. The friction properties were evaluated based on the wear testing and mechanical properties were evaluated from the tensile tests based on Young's modulus (E) and tensile strength (Rm) values. Used nanofillers caused decreasing of friction and mechanical properties of PVDF nanocomposite material films.Web of Science1418art. no. 383

Phase transformation after heat treatment of Cr-Ni stainless steel powder for 3D printing

Today, Ni-Cr steel is used for advanced applications in the high-temperature and electrical industries, medical equipment, food industry, agriculture and is applied in food and beverage packaging and kitchenware, automotive or mesh. A study of input steel powder from various stages of the recycling process intended for 3D printing was conducted. In addition to the precise evaluation of the morphology, particle size and composition of the powders used for laser 3D printing, special testing and evaluation of the heat-treated powders were carried out. Heat treatment up to 950 degrees C in an air atmosphere revealed the properties of powders that can appear during laser sintering. The powders in the oxidizing atmosphere change the phase composition and the original FeNiCr stainless steel changes to a two-phase system of Fe3Ni and Cr2O3, as evaluated by X-ray diffraction analysis. Observation of the morphology showed the separation of the oxidic phase in the sense of a brittle shell. The inner part of the powder particle is a porous compact core. The particle size is generally reduced due to the peeling of the oxide shell. This effect can be critical to 3D printing processing, causing defects on the printed parts, as well as reducing the usability of the precursor powder and can also change the properties of the printed part.Web of Science1515art. no. 534

Antimicrobial PVDF nanofiber composites with the ZnO - vermiculite - chlorhexidine based nanoparticles and their tensile properties

The poly(vinylidene fluoride) (PVDF) nanofiber materials have attracted attention due to their enhanced and exceptional nanostructural characteristics. Electrospinning PVDF based nanofiber is one of the important new materials for the rapidly growing technology development such as nanofiber based conductive tissue engineering, scaffold materials, filters and medical textiles applications. At these areas the risk of microbial contamination is very high, hence in this study the PVDF nanofiber materials with antimicrobial zinc oxide (ZnO), zinc oxide/vermiculite (ZnO/V), zinc oxide/vermiculite-chlorhexidine (ZnO/V_CH) and vermiculite-chlorhexidine (V_CH) nanofillers were prepared by electrospinning, via one-step electrospinning process. The PVDF nanofiber diameters and their orientation were investigated using scanning electron microscope (SEM). The ZnO/V_CH and V/CH nanofillers with positive ζ - potential values were incorporated into PVDF nanofibers with an average diameter of 108 nm for PVDF_ZnO/V_CH and 100 nm for PVDF_V_CH samples. In contrast, ZnO and ZnO/V nanofillers with negative ζ - potential values reacted intensively with PVDF polymer. The slightly hydrophobe character was demonstrated by water contact angle from ∼100°. The chemical interactions were evaluated by the Fourier transform infrared spectroscopy (FTIR). The presence of the β-phase in the original PVDF and the small traces of the α-phase in PVDF_ZnO and PVDF_ZnO/V samples was confirmed. In the PVDF_ZnO/V_CH and PVDF_V/CH samples where the specific interaction of PVDF chains with CH a rapid decrease in the β-phase fraction was evaluated. The mechanical properties based on the Young's modulus (E) and tensile strength (Rm) values were evaluated from the tensile test curves. Antimicrobial activity (longer than 48 h) against S. aureus and E. coli for PVDF_ZnO/V_CH and PVDF_V/CH samples was obtained. © 2021[SP2020/08]; [SP2021/106

Functional properties of polyurethane ureteral stents with PLGA and papaverine hydrochloride coating

Despite the obvious benefits of using ureteral stents to drain the ureters, there is also a risk of complications from 80-90%. The presence of a foreign body in the human body causes disturbances in its proper functioning. It can lead to biofilm formation on the stent surface, which may favor the development of urinary tract infections or the formation of encrustation, as well as stent fragmentation, complicating its subsequent removal. In this work, the effect of the polymeric coating containing the active substance-papaverine hydrochloride on the functional properties of ureteral stents significant for clinical practice were assessed. Methods: The most commonly clinically used polyurethane ureteral Double-J stent was selected for the study. Using the dip-coating method, the surface of the stent was coated with a poly(D,L-lactide-glycolide) (PLGA) coating containing the papaverine hydrochloride (PAP). In particular, strength properties, retention strength of the stent ends, dynamic frictional force, and the fluoroscopic visibility of the stent during X-ray imaging were determined. Results: The analysis of the test results indicates the usefulness of a biodegradable polymer coating containing the active substance for the modification of the surface of polyurethane ureteral stents. The stents coated with PLGA+PAP coating compared to polyurethane stents are characterized by more favorable strength properties, the smaller value of the dynamic frictional force, without reducing the fluoroscopic visibility.Web of Science2214art. no. 770

Difuzní charakteristika a koncentračně gradientní materiálz na bázi Ni-Al

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta metalurgie a materiálového inženýrství. Katedra (637) neželezných kovů, rafinace a recyklac

Strukturní a mechanické charakteristiky slitin na bázi Ni3Al po směrové krystalizaci

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta metalurgie a materiálového inženýrství. Katedra (637) neželezných kovů, rafinace a recyklac

Engineering practical aspect of material degradation due to Kirkendall effect

The diffusion joints of Ni/Ni3Al were prepared by electron beam welding in vacuum furnace and diffusion annealing at three different temperature (1000, 1100 and 1140°C) and for different annealing time. The microstructure properties were investigated before and after diffusion annealing by means of light and scanning electron microscopes. In the context of the concentration changes microstructure changes and Kirkendall voids occurrence were observed. The obtained results were completed by surface topography of Kirkendall voids in etched specimens by atomic force microscopy (AFM)

Characterization of vermiculite particles after different milling techniques

The natural Mg-vermiculite (VB) from Brazil and its Na-form (Na-VB) was studied after milling in ball, jet and vibrational mills. The morphology of vermiculite samples was studied using scanning electron microscopy (SEM) and the changes of vermiculite structures were monitored using X-ray diffraction (XRD) analysis. The particle size (PS) changes were characterized by the median particle size (d50), volume-weighted mean diameter (d43), mode diameter (dm) and span value. The surface changes of vermiculite samples were evaluated using ξ-potential measurements as a function of particle electrophoretic mobility (μ). The electrophoretic mobility (μ) of the VB and its milled samples was in the range of 1.16 to 1.96 × 10− 4 m2/Vs and of the Na-VB and its milled samples were in range of 3.44 to 4.25 × 10− 4 m2/Vs. The range of the difference in the ξ-potential of the VB was from − 15.1 to − 25.4 mV and Na-VB was from − 55 mV to the − 44.5 mV. Samples containing small particles and homogeneous particle size distribution showed a low value of ξ-potentialWeb of Science23928327