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

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

CuO and CuO/vermiculite based nanoparticles in antibacterial PVAc nanocomposites

Copper oxide (CuO) nanoparticles are used in a wide range of applications due to its specific chemical, surface and microstructural characteristics, excellent physicochemical properties and cost effectiveness. The combination of the CuO with the vermiculite (V) particles allows to the preparation of nanostructured materials with specific properties. CuO nanoparticles were prepared by sonochemical synthetic method followed by a heat treatment (at 350 degrees C for 90 min) with the used of Cu(NO3)(2) and NaOH precursors. Natural V was used for nanocomposite structures preparation (CuO/V). The nanostructured samples were characterized using scanning electron microscopy and X-ray diffraction. The particle size (median diameter, d(50)), xi-potential and specific surface area were analysed. The antibacterial efficiency was evaluated by finding the minimum inhibitory concentration against Staphylococcus aureus and Enterococcus faecalis. The polyvinyl acetate (PVAc) nanocomposite plates were prepared using 0.1, 0.5 and 1 wt% of CuO (respectively CuO/V) nanostructured materials as functional nanofillers and were characterized by X-ray diffraction, scanning electron microscopy and 3D optical light microscope. The positive effect of vermiculite particles on homogeneous distribution in PVAc matrix was shown. The antibacterial activity was evaluated against Staphylococcus aureus and Enterococcus faecalis. Significant antibacterial behavior with long-acting after 24 h against Staphylococcus aureus was evaluated for all PVAc nanocomposites. The results show that already 0.1 wt% of CuO nanofillers (respectively CuO/V) in the PVAc matrix produce an antibacterial surface against Staphylococcus aureus.Web of Scienc

Cobalt-organovermiculite arrangement and mechanical properties: models and experiments

The layered structure of the clay mineral, vermiculite, was organophilized with amine molecules and ammonium cations. Enrichment with cobalt was obtained using intercalative process in aqueous environment for ammonium cations and melting-milling intercalation for amine. Each of Co-organovermiculites represents different type of arrangement in clays gallery as revealed by molecular models. Cations Co2+ are partly immersed in to silicate layer and aliphatic chains of ammonium cations are repelled form place of metal cation interaction. Amine in organovermiculite is arranged as lateral double-layer molecules and cobalt atom is positioned in random place in the gallery. Based on the modeled data the properties and mechanical parameters of both Co- organovermiculites was established. Very high compressibility value (82.5 TPa–1) of CoHDTMA-VMT results from the paraffin-like arrangement in the clay gallery and low density 1.25 g · cm–3. CoDDA-VMT low compressibility (3.5 TPa –1) because it is closely packed system with inorganic and organic species in vermiculite interlayer; density is higher 2.031 g · cm–3. Bulk and shear modulus are smaller for CoHDTMA-VMT.Web of Science11112392238

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 degrees 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.Web of Science1953048304

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 zeta-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 zeta-potential and other physical and chemical properties are important in ascertaining positive and negative aspects of metallic nanoparticles in future applications and related research.Web of Science19127933792