The Effect of Clay Type on the Physicochemical Properties of New Hydrogel Clay Nanocomposites

This study focuses on the investigation of clay type effect on the final properties of semi-interpenetrated Salecan/poly(methacrylic acid)/clay hydrogel nanocomposites. Previous studies have indicated that the presence of clay in polymer composites leads to better swelling capacity and mechanical properties as functions of clay type. On the other hand, Salecan, which is a water soluble extracellular polysaccharide, was proved to assure greater flexibility to hydrogels. These properties recommend clay and Salecan for semi-interpenetrated hydrogels preparation with specific application in biomedicine. The purpose was to determine the most suitable type of clay as well as Salecan influence for developing the desired water retention/delivery ability and mechanically enhanced semi-interpenetrating polymer network (SIPN) nanocomposites. For our investigations, we have chosen commercially available montmorillonite (ClNa) and different commercial organomodified clay (Cl30B, Cl20A and Cl15A). Several analyses results (FTIR, TGA, DMA, XRD, microscopy and swelling studies) demonstrated that not only the presence of Salecan but also the clay type influenced the structure and properties of the final nanocomposites

Hydrophobic Carbonate Coatings on Pure Biodegradable Mg by Immersion in Carbonated Water: Formation Mechanism

Mg is one of the few materials of choice for biodegradable implants, despite its rapid degradation when used without surface protection treatment. This study presents the effect of carbonation time on the formation of hydrophobic carbonate coatings grown on pure magnesium using a simple, green chemical conversion method in carbonated water. The evolution of the coating with immersion time in carbonating solution was studied in order to ascertain the mechanistic of coating formation by Raman and EDS spectroscopy, XRD, SEM and AFM microscopy. Wettability was investigated by contact angle measurements. The formation mechanism of the hydrophobic coating involves the surface nucleation of carbonates mediated by the dissolution of the native corrosion product, brucite Mg(OH)2, surface conversion into hydroxycarbonates, surface calcite nucleation and growth by attachment of nanoparticles, leading to the lateral growth of a continuous carbonate coating layer of intertwined calcite microcrystals

Hydrophobic Carbonate Coatings on Pure Biodegradable Mg by Immersion in Carbonated Water: Formation Mechanism

Mg is one of the few materials of choice for biodegradable implants, despite its rapid degradation when used without surface protection treatment. This study presents the effect of carbonation time on the formation of hydrophobic carbonate coatings grown on pure magnesium using a simple, green chemical conversion method in carbonated water. The evolution of the coating with immersion time in carbonating solution was studied in order to ascertain the mechanistic of coating formation by Raman and EDS spectroscopy, XRD, SEM and AFM microscopy. Wettability was investigated by contact angle measurements. The formation mechanism of the hydrophobic coating involves the surface nucleation of carbonates mediated by the dissolution of the native corrosion product, brucite Mg(OH)2, surface conversion into hydroxycarbonates, surface calcite nucleation and growth by attachment of nanoparticles, leading to the lateral growth of a continuous carbonate coating layer of intertwined calcite microcrystals

Photocatalytic Behavior of Water-Based Styrene-Acrylic Coatings Containing TiO2 Sensitized with Metal-Phthalocyanine Tetracarboxylic Acids

The study presents the results regarding the photocatalytic behavior of some water-based styrene-acrylic coatings containing TiO2 nanoparticles sensitized with metal-phthalocyanine tetracarboxylic acids. Coating materials have been studied in terms of color characteristics, photocatalytic behavior, and resistance to self-degradation depending on the structure of phthalocyanine sensitizers. Coatings that were exposed to Xenon light showed degradation of the organic sensitizer rather than of the binder. Photocatalytic tests using methylene blue as a standard contaminant indicated that the coating containing TiO2 nanoparticles sensitized with Fe(III) phthalocyanine tetracarboxylic acids showed the highest efficiency both in ultraviolet or visible light. In this case, the UV light induced a photodegradation rate that was greatly increased of about fifty times comparatively with that induced by LED light and was determined by two different mechanisms, but side reactions like methylene blue and sensitizer self destruction are possible to occur simultaneously. Photocatalytic materials of this type are suitable to be used as decorative coatings especially for indoor applications

Synthesis of Zinc Oxide Nanomaterials via Sol-Gel Process with Anti-Corrosive Effect for Cu, Al and Zn Metallic Substrates

Nanosized zinc oxide (ZnO) particles modified with different silane coupling agents (octyltriethoxysilane (OTES), octadecyltriethoxysilane (ODTES) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS)) were synthesized in basic catalysis using the sol-gel method. The structure and morphology were characterized by dynamic light scattering (DLS), environmental scanning electron microscopy (ESEM) and Fourier transform infrared spectroscopy (FTIR) for bonding characteristics. The final hybrid materials were deposited on three types of metallic substrates (aluminum (Al), copper (Cu) and zinc (Zn)) in order to obtain coatings with ultrahydrophobic and anti-corrosion properties. Water wettability was studied revealing a contact angle of 145° for the surface covered with ZnO material modified with ODTES. The water contact angle increased with the length of the alkyl chain supplied by the silica precursor. The anti-corrosive behavior of ZnO/silane coupling agents particles deposited on metallic substrates was studied by the linear polarization technique in neutral medium

The Immobilization of Laccase on Mixed Polymeric Microspheres for Methyl Red Decomposition

Means of eliminating water pollutants or transforming them into less hazardous compounds by green catalysis are desired. The current work was developed with the goal of discovering supports suited for laccase (Lc) immobilization. The effect of the chitosan (CS) molecular weight (Mw) or the polyacrylic acid (PAA) addition was evaluated in microsphere formulation and enzyme immobilization by ESEM, rheology, operational stability, and kinetics. As a practical application, the synthesized products were tested in the methyl red (MR) decomposition and the product identification was performed by high-resolution mass spectrometry. Depending on the required properties, the laccase activity profile (pH, temperature, storage, and Michaelis–Menten parameters) and rheological strength can be modulated by varying the molecular mass of CS or by adding PAA in the support formulation. The immobilized products having the best features regarding MR degradation and recycling abilities were the medium Mw CS microspheres and the system with low Mw CS complexed by PAA, respectively. The degradation mechanism of the dye was proposed accordingly with the identified products by mass spectroscopy. The findings emphasize the potential of the proposed immobilization products to be exploited as viable biocatalysts for dye-contaminated water

Novel Green Crosslinked Salecan Hydrogels and Preliminary Investigation of Their Use in 3D Printing

Salecan, a kind of polysaccharide, is produced by the Agrobacterium ZX09 salt tolerant strain. In this study, green crosslinked citric acid-salecan hydrogels are explored as novel materials with a high potential for use in regenerative medicine. The impact of salecan and citric acid on the final crosslinked hydrogels was intensively studied and estimated in terms of the whole physicochemical properties and antimicrobial activity. FTIR spectra demonstrated the successful green crosslinking of salecan through its esterification with citric acid where the formation of strong covalent bonds collaboratively helped to stabilize the entire hydrogel systems in a wet state. Hydrogels presented a microporous morphology, good swelling capacity, pH responsiveness, great mechanical stability under stress conditions and good antibacterial activity, all related to the concentration of the biopolymers used in the synthesis step. Additionally, salecan hydrogels were preliminary investigated as printing inks. Thanks to their excellent rheological behavior, we optimized the citrate-salecan hydrogel inks and printing parameters to render 3D constructs with great printing fidelity and integrity. The novel synthesized salecan green crosslinked hydrogels enriches the family of salecan-derived hydrogels. Moreover, this work not only expands the application of salecan hydrogels in various fields, but also provides a new potential option of designing salecan-based 3D printed scaffolds for customized regenerative medicine

Novel Green Crosslinked Salecan Hydrogels and Preliminary Investigation of Their Use in 3D Printing

Salecan, a kind of polysaccharide, is produced by the Agrobacterium ZX09 salt tolerant strain. In this study, green crosslinked citric acid-salecan hydrogels are explored as novel materials with a high potential for use in regenerative medicine. The impact of salecan and citric acid on the final crosslinked hydrogels was intensively studied and estimated in terms of the whole physicochemical properties and antimicrobial activity. FTIR spectra demonstrated the successful green crosslinking of salecan through its esterification with citric acid where the formation of strong covalent bonds collaboratively helped to stabilize the entire hydrogel systems in a wet state. Hydrogels presented a microporous morphology, good swelling capacity, pH responsiveness, great mechanical stability under stress conditions and good antibacterial activity, all related to the concentration of the biopolymers used in the synthesis step. Additionally, salecan hydrogels were preliminary investigated as printing inks. Thanks to their excellent rheological behavior, we optimized the citrate-salecan hydrogel inks and printing parameters to render 3D constructs with great printing fidelity and integrity. The novel synthesized salecan green crosslinked hydrogels enriches the family of salecan-derived hydrogels. Moreover, this work not only expands the application of salecan hydrogels in various fields, but also provides a new potential option of designing salecan-based 3D printed scaffolds for customized regenerative medicine

Influence of the Hydrophobicity of Pluronic Micelles Encapsulating Curcumin on the Membrane Permeability and Enhancement of Photoinduced Antibacterial Activity

Apart from its well-known activity as an antimicrobial agent, Curcumin (CURC) has recently started to arouse interest as a photosensitizer in the photodynamic therapy of bacterial infections. The aim of the present study was to evidence the influence of the encapsulation of Curcumin into polymeric micelles on the efficiency of photoinduced microbial inhibition. The influence of the hydrophobicity of the selected Pluronics (P84, P123, and F127) on the encapsulation, stability, and antimicrobial efficiency of CURC-loaded micelles was investigated. In addition, the size, morphology, and drug-loading capacity of the micellar drug delivery systems have been characterized. The influence of the presence of micellar aggregates and unassociated molecules of various Pluronics on the membrane permeability was investigated on both normal and resistant microbial strains of E. coli, S. aureus, and C. albicans. The antimicrobial efficiency on the common pathogens was assessed for CURC-loaded polymeric micelles in dark conditions and activated by blue laser light (470 nm). Significant results in the reduction of the microorganism’s growth were found in cultures of C. albicans, even at very low concentrations of surfactants and Curcumin. Unlike the membrane permeabilization effect of the monomeric solution of Pluronics, reported in the case of tumoral cells, a limited permeabilization effect was found on the studied microorganisms. Encapsulation of the Curcumin in Pluronic P84 and P123 at very low, nontoxic concentrations for photosensitizer and drug-carrier, produced CURC-loaded micelles that prove to be effective in the light-activated inhibition of resistant species of Gram-positive bacteria and fungi

Synthesis, Characterization, DFT Study and Antifungal Activities of Some Novel 2-(Phenyldiazenyl)phenol Based Azo Dyes

In recent decades, there has been an increased interest in azo compounds with special optical and biological properties. In this work, we report the preparation of novel azo-compounds with two and three –N=N- double bonds, using the classical method of synthesis, diazotization and coupling. The compounds were characterized by 1H-NMR, 13C-NMR, FTIR, UV-VIS and fluorescence spectra. DFT calculations were employed for determining the optical parameters, polarizability α, the total static dipole moment μtot, the quadrupole moment Q and the mean first polarizability βtot. All azo derivatives show strong fluorescence emission in solutions. The antioxidant and antifungal activities were determined and the influence of the number of azo bonds was discussed. The synthesized compounds exhibit remarkable efficiency in the growth reduction of standard and clinical isolated Candida strains, suggesting future applications as novel antifungal