Alkali-Treated Alumina and Zirconia Powders Decorated with Hydroxyapatite for Prospective Biomedical Applications.

The alumina and zirconia surfaces were pretreated with chemical etching using alkaline mixtures of ammonia, hydrogen peroxide and sodium hydroxide, and followed with application of the powder layer of Ca-deficient hydroxyapatite (CDH). The influence of etching bath conditions time and concentration on surface development, chemical composition and morphology of medicinal ceramic powders were studied. The following analyses were performed: morphology (scanning electron microscopy), phase composition (X-ray diffraction analysis), changes in binding interactions and chemical composition (FT-Infrared and Energy dispersive spectroscopies). Both types of etchants did not expose the original phase composition changes or newly created phases for both types of ceramics. Subsequent decoration of the surface with hydroxyapatite revealed differences in the morphological appearance of the layer on both ceramic surfaces. The treated zirconia surface accepted CDH as a flowing layer on the surface, while the alumina was decorated with individual CDH aggregates. The goal of this study was to focus further on the ceramic fillers for polymer-ceramic composites used as a biomaterial in dental prosthetics.

Various Simulated Body Fluids Lead to Significant Differences in Collagen Tissue Engineering Scaffolds.

This study aims to point out the main drawback with respect to the design of simulated body environments. Three media commonly used for the simulation of the identical body environment were selected, i.e., Kokubo's simulated body fluid that simulates the inorganic component of human blood plasma, human blood plasma, and phosphate buffer saline. A comparison was performed of the effects of the media on collagen scaffolds. The mechanical and structural effects of the media were determined via the application of compression mechanical tests, the determination of mass loss, and image and micro-CT analyses. The adsorption of various components from the media was characterized employing energy-dispersive spectrometry. The phase composition of the materials before and after exposure was determined using X-ray diffraction. Infrared spectroscopy was employed for the interpretation of changes in the collagen secondary structure. Major differences in terms of the mechanical properties and mass loss were observed between the three media. Conversely, only minor structural changes were detected. Since no general recommendation exists for selecting the simulated body environment, it is necessary to avoid the simplification of the results and, ideally, to utilize alternative methods to describe the various aspects of degradation processes that occur in the media.

Polylactide Composites Suitable for Medical Devices.

Biodegradable polymeric materials with antimicrobial surfaces could be a suitable alternative for production of medical devices, especially if they are prepared in form of composites containing functional matter. Their greatest advantage is that they do not need to be removed from patient's body and simultaneously they can prevent growth of biofilm. In this work, polymeric films of polylactide acid with biosynthetically prepared silver nanoparticles, commercial multiwall carbon nanotubes and organovermiculite with hexadecyltrimethylammonium bromide in various concentrations were prepared to get polylactide composite with antibacterial properties. The dispersibility of filler in matrix was one of the key issues to be controlled in nanocomposite. Using several analytical techniques and observing morphology of prepared composite it was found that best results provide organovermiculite filler. For the tests of functionality antimicrobial tests were performed.

Stability of Calcium Deficient Hydroxyapatite/Clay Mineral Nanocomposite in Solutions with Different pH.

Hydroxyapatite is one of the building blocks of hard tissues of living organisms. Therefore stability of nanoparticles in experimental solutions of different pH similar to one in human body is important issue for precise tailoring of the synthesis of hydroxyapatite particles on clay mineral substrate. In this study, the stability (amount of CaII and PV released into the water) of calcium deficient hydroxyapatite/clay mineral nanocomposites was investigated. The calcium deficient hydroxyapatite/clay mineral nanocomposites with montmorillonite and two vermiculites (Brazil and Bulgaria) were compared with pure calcium deficient hydroxyapatite. The stability was investigated for 24 h where calcium deficient hydroxyapatite/clay mineral nanocomposites and pure calcium deficient hydroxyapatite were placed into the water solutions with different pH values (pH= 5, 7, and 9). The presence of CaII and PV ions at solutions were determined using atomic emission spectrometry. The calcium deficient hydroxyapatite/clay mineral nanocomposites after stability testing were characterized by X-ray powder diffraction and infrared spectroscopy with Fourier transformation.

Study of the Optimum Arrangement of Spherical Particles in Containers Having Different Cross Section Shapes.

Fluidized bed porosity ɛ is a primary property of fluidized systems when determining the minimum floating velocity. The air flow rate in the fluidized bed (or in the fluid layer of the material) increases with diminishing bed porosity. This paper is devoted to porosity calculations for a fluidized bed consisting of spherical particles having different diameters (2, 4, 6, 8, 10 mm) and in differently shaped polygonal fluidized bed cells possessing different characteristic particle floating velocities. For testing purposes, porosity was experimentally measured and subsequently modelled by simulation using the Rocky code. Cells with regular triangular, tetragonal (square-shaped), pentagonal, hexagonal, heptagonal and circular cross sections were used for the experiment. All the cells possessed the same cross-section area S = 1256 mm². The weight of the spherical particle batch in the experiments was constant, 2 kg, for all of the fluidized bed cell cross section shapes described above.

Effect of Milling and Annealing on Carbon-Silver System.

Mechanical treatment of graphite silver mixture followed by heat treatment showed morphology and structure changes of both components. Silver is being distributed over graphite flakes randomly with higher concentration on the edges and nanometric size, which was observed using scanning and transmission electron microscopy. The annealing temperature 1300 °C is higher than melting temperature of silver (961.8 °C) and base on phase diagram C-Ag (C. L. Chen, et al., Appl. Phys. Lett. 96, 253104 (2010).) silver is being transferred from liquid phase to solid phase at rapid cooling, which is giving various crystallinity.

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.

Silver/Chitosan Antimicrobial Nanocomposites Coating for Medical Devices: Comparison of Nanofiller Effect Prepared via Chemical Reduction and Biosynthesis.

Medical devices have an essential part in healthcare system in recent years, such as usage of heart valves, several types of stents and implants devices in patients. However, bacterial infection of medical devices causes critical issues for patients due to attachment of bacteria and formation of biofilm onto the medical devices. Therefore, finding an effective antibacterial coating to prevent biofilm formation and infection is our goal. In this study, we developed silver/chitosan nanocomposites for antimicrobial coating system by chemical and green methods using sodium borohydride and linden extract, respectively. Silver is known as a strong inorganic antimicrobial agent to kill bacteria by inactivating enzymes and dysfunction bacterial cell membranes. By immobilizing silver nanoparticles on chitosan biopolymer can prevent agglomeration of nanoparticles, besides it can improve the biocompatibility. We characterized properties of our silver chitosan nanocomposites samples using particle size distribution, ultraviolet-visible spectroscopy, X-ray diffraction analysis and scanning electron microscopy. Effective antimicrobial film preventing biofilm formation on medical devices was designed. Antimicrobial testing confirmed antimicrobial properties however variable for each type of nanosilver.

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.

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.

Antimicrobial nanocomposites based on natural modified materials: a review of carbons and clays.

The review is focused on the recent research and development of antimicrobial nanocomposites based on selected carbon nanomaterials and natural nanoclay minerals. The nanocomposites comprised of two or several components, where at least one presents antimicrobial properties, are discussed. Yet the most popular agent remains silver as nanoparticle or in ionic form. Second, broadly studied group, are organics as additives or polymeric matrices. Both carbons and clays in certain forms possess antimicrobial properties. A lot of interest is put on to research graphene oxide. The low-environmental impact technologies-based on sustainable biopolymers have been studied. Testing of antimicrobial properties of nanomaterials is performed most frequently on E. coli and S. aureus bacterias.

Modified clay minerals efficiency against chemical and biological warfare agents for civil human protection.

Sorption efficiencies of modified montmorillonite and vermiculite of their mono ionic Na and organic HDTMA and HDP forms were studied against chemical and biological warfare agents such as yperite and selected bacterial strains. Yperite interactions with modified clay minerals were observed through its capture in low-density polyethylene foil-modified clay composites by measuring yperite gas permeation with using chemical indication and gas chromatography methods. The antibacterial activities of synthetized organoclays were tested against selected Gram-positive and Gram-negative bacterial species in minimum inhibitory concentration tests. The obtained results showed a positive influence of modified clay minerals on the significant yperite breakthrough-time increase. The most effective material was the polyethylene-Na form montmorillonite, while the polyethylene-Na form vermiculite showed the lowest efficiency. With increasing organic cations loading in the interlayer space the montmorillonite efficiency decreased, and in the case of vermiculite an opposite effect was observed. Generally the modified montmorillonites were more effective than modified vermiculites. The HDP cations seem to be more effective compare to the HDTMA. The antibacterial activity tests confirmed efficiency of all organically modified clay minerals against Gram-positive bacteria. The confirmation of antibacterial activity against Y. pestis, plague bacteria, is the most interesting result of this part of the study.

Preparation of organovermiculites using HDTMA: structure and sorptive properties using naphthalene.

Three types of organovermiculites with various organic cation (HDTMA) loading were prepared to be used as sorptive material for non-ionic organic compounds. The prepared materials were characterized using XRD and TOC analysis. The experiments evolved the fact that lower loading of HDTMA is more acceptable for sorption of neutral organic molecules from aqueous solutions. One of the possible models of intercalated molecules arrangement in vermiculite spacing was proposed.

Silver nanoparticles/montmorillonite composites prepared using nitrating reagent at water and glycerol.

Three procedures (P) were applied to prepare silver nanoparticles on natural Ca-montmorillonite (MT). The intercalation of the montmorillonite with silver nitrate in aqueous solution (P1), the intercalation of the montmorillonite with silver nitrate in glycerol (P2) and the successive combination of both P1 and P2 methods resulted to P3 method. X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Fourier Transform Infrared (FTIR) spectroscopy and the molecular modeling were employed to characterize silver nanoparticles and montmorillonite nanocomposite. The P1 produced MT-1 composite with 2.3 wt% Ag and the partially collapsed layered structure. Nanoparticles of silver larger than 20 nm with a lot of planar defects were randomly distributed on the MT-1 surface; nanoparticles smaller than 20 nm were oriented to the montmorillonite substrate. The MT-2 composite from P2 contained only 1 wt% of Ag. The molecular simulation model of MT-2 showed the interlayer space with the exchangeable cations and metallic silver atoms arrangement within the glycerol bilayer. The P3 produced composite MT-3 that contained 2.4 wt% Ag. The nanoparticles > 20 nm size had a well-defined geometry, very small nanoparticles were amorphous. The modeled structure showed the exchangeable cations, Ag+ and Ag0 located close to the silicate layers and monolayer of glycerol molecules in the interlayer space.

Fluorescence and structure of methyl red-clay nanocomposites.

Two types of clay minerals-montmorillonite and vermiculite have been chosen as a host matrix for the intercalation of methyl red (MR) in order to investigate a possible fluorescence tuning via dye-clay interactions. The effect of silicate layer charge on the structure and fluorescence of dye-clay intercalated hybrid nanostructures was investigated using combination of molecular modeling with experiment. Structure of both intercalates MR-vermiculite (MR-VER) and MR-montmorillonite (MR-MMT) exhibits high degree of structural disorder resulting in broaden emission band. The fluorescence wavelength range of MR intercalated in clays is shifted to lower wavelengths compared with the pristine MR polycrystalline sample (800 nm). Results showed the strong dependence of fluorescence band maximum on the silicate layer charge, lambda(max) = 565 nm for MR-MMT, 645 nm for MR-VER and 800 nm for the methyl red fine crystalline powder, whereas the structural disorder in the arrangement of dye molecules affects the emission band broadening.