Cellulose Fabrics Functionalized with Sol-Gel Photocatalytic Coatings Based on Iron (III) Phthalocyanine Tetracarboxylic Acids-TiO2-Silica Hybrids

Photocatalytic coatings are difficult to obtain on textile materials because of the sometimes contradictory properties that must be achieved. In order to obtain a high efficiency of a photocatalytic effect, the metal-oxide semiconductor must be found in the vicinity of the coating-air interface in order to come into direct contact with the contaminant species and allow light radiation access to its surface. Another necessary condition is related to the properties of the covering textile material as well as to the stability of the xerogel films to light and wet treatments. In this sense, we proposed a solution based on hybrid silica films generated by sol-gel processes, coatings that contain as a photocatalyst TiO2 sensitized with tetracarboxylic acid of iron (III) phthalocyanine (FeTCPc). The coatings were made by the pad-dry-cure process, using in the composition a bifunctional anchoring agent (3-glycidoxipropyltrimethoxysilane, GLYMO), a crosslinking agent (sodium tetraborate, BORAX), and a catalyst (N-methylimidazole, MIM) for the polymerization of epoxy groups. The photodegradation experiments performed on methylene blue (MB), utilized as a model contaminant, using LED or xenon arc as light sources, showed that the treatment with BORAX improves the resistance of the coatings to wet treatments but worsens their photocatalytic performances.

Single- and Multilayer Build-Up of an Antibacterial Temperature- and UV-Curing Sol-Gel System with Atmospheric Pressure Plasma

The versatility of sol-gel systems makes them ideal for functional coatings in industry. However, existing coatings are either too thin or take too long to cure. To address these issues, this paper proposes using an atmospheric pressure plasma source to fully cure and functionalize thicker sol-gel coatings in a single step. The study explores coating various substrates with sol-gel layers to make them scratch-resistant, antibacterial, and antiadhesive. Microparticles like copper, zinc, or copper flakes are added to achieve antibacterial effects. The sol-gel system can be sprayed on and quickly functionalized on the substrate. The study focuses on introducing and anchoring particles in the sol-gel layer to achieve an excellent antibacterial effect by changing the penetration depth. Overall, this method offers a more efficient and effective approach to sol-gel coatings for industrial applications. In order to achieve a layer thickness of more than 100 µm, the second part of the study proposes a multilayer system comprising 15 to 30 µm thick monolayers that can be modified by introducing fillers (such as TiO2) or scratch-resistant chemicals like titanium isopropoxide. This system also allows for individual plasma functionalization of each sol-gel layer. For instance, the top layer can be introduced with antibacterial particles, while another layer can be enhanced with fillers to increase wear resistance. The study reveals the varying antibacterial effects of spherical particles versus flat flakes and the different scratch hardnesses induced by changes in pH, number of layers, and particle introduction.

Formation of Composite Coatings on Galvanized Steel from Organosilane Solutions Using Electrophoresis and Sol-Gel Technology

New hybrid composite coatings (HCCs) on hot-dip galvanized steel (HDGS) were obtained using electrophoresis (cathodic polarization (CP)) and sol–gel technology. For this purpose, a technique for the preparation of a cationic precursor based on TiCl₄ and aminopropyltriethoxysilane was developed. Electrophoresis of the charged particles of the precursor and organosilanes promotes the production of denser sol–gel coatings with improved adhesion. Using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) methods, the formation mechanism and protective properties of HCC on galvanized steel were investigated.

Hybrid Sol-Gel Silica Coatings Containing Graphene Nanosheets for Improving the Corrosion Protection of AA2024-T3

In the present work, nanostructured graphene nanosheets were added to hybrid silica sols and deposited on aluminium alloy A2024-T3 to study the effect on the corrosion behaviour. Sols were prepared using tetraethyl-orthosilicate (TEOS), 3-glycidoxypropyl-trimethoxysilane (GPTMS) and a colloidal silica suspension (LUDOX) as silica precursors with adding chemically modified graphene nanosheets (GN-chem). The graphene nanosheets were modified through a straightforward and simple hydrothermal approach and then, dispersed into a silica sol (SiO2/GN-chem). ATR-FTIR was used to optimize the silica sol-gel synthesis and to confirm the cross-linking of the silica network. The corrosion behaviour of the SiO2/GN-chem coatings was also analysed by electrochemical measurement (potentiodynamic polarization) in 0.05 M NaCl solution. The results showed that the incorporation of modified graphene nanosheets into hybrid silica sol-gel coatings affected the corrosion properties of the substrates. An improvement in the corrosion resistance was observed likely due to the enhanced barrier property and hydrophobic behaviour obtained by incorporation of GN-chem and colloidal silica nanoparticles.

Enhanced cytocompatibility and osteoinductive properties of sol-gel-derived silica/zirconium dioxide coatings by metformin functionalization

The aim of this study was to evaluate the pro-osteogenic properties of sol-gel-derived silica/zirconium dioxide coatings functionalized with 1 mM of metformin. The matrices were applied on 316L stainless steel using dip-coating technique. First of all, physicochemical properties of biomaterials were evaluated. Surface morphology and topography was determined using energy-dispersive X-ray spectroscopy and atomic force microscopy. The chemical composition was evaluated using Fourier transform infrared spectroscopy. Further, wettability and surface free energy were characterized. Cytocompatibility of biomaterials was tested in vitro using model of human multipotent mesenchymal stromal cells isolated from adipose tissue. The influence of biomaterials on cells morphology and proliferation was determined. Osteogenic effect of obtained biomaterials was evaluated in terms of their influence on secretory activity of human multipotent mesenchymal stromal cells isolated from adipose tissue and matrix mineralization. Analysis was performed in relation to the control cultures i.e. maintained on pure SS316L substrate and SS316L covered with silica/zirconium dioxide. Obtained results indicate that silica/zirconium dioxide_metformin coatings ameliorated metabolic and proliferative activity of human multipotent mesenchymal stromal cells isolated from adipose tissue, as well as promoted their proper growth and adhesion. The human multipotent mesenchymal stromal cells isolated from adipose tissue cultured on biomaterials were characterized by typical fibroblast-like morphology. The addition of metformin to the silica/zirconium dioxide coatings improved functional differentiation of human multipotent mesenchymal stromal cells isolated from adipose tissue. Osteogenic cultures on silica/zirconium dioxide_metformin were characterized by formation of well-developed osteonodules rich in calcium and phosphorous. Moreover, human multipotent mesenchymal stromal cells isolated from adipose tissue cultured on silica/zirconium dioxide_metformin synthesized increased amount of alkaline phosphatase, bone morphogenetic protein 2 and osteopontin, both on messenger RNA and protein level. Obtained biomaterials modulate cellular plasticity of human multipotent mesenchymal stromal cells isolated from adipose tissue promoting their osteogenic differentiation, thus may find application in broadly defined tissue engineering.

Cytokine induction of sol-gel-derived TiO2 and SiO2 coatings on metallic substrates after implantation to rat femur

Material surface is a key determinant of host response on implanted biomaterial. Therefore, modification of the implant surface may optimize implant–tissue reactions. Inflammatory reaction is inevitable after biomaterial implantation, but prolonged inflammation may lead to adverse reactions and subsequent implant failure. Proinflammatory activities of cytokines like interleukin (IL)-1, IL-6, and tumor necrosis factor-alpha (TNF-α) are attractive indicators of these processes and ultimately characterize biocompatibility. The objective of the study was to evaluate local cytokine production after implantation of stainless steel 316L (SS) and titanium alloy (Ti6Al4V) biomaterials coated with titanium dioxide (TiO₂) and silica (SiO₂) coatings prepared by sol–gel method. Biomaterials were implanted into rat femur and after 12 weeks, bones were harvested. Bone–implant tissue interface was evaluated; immunohistochemical staining was performed to identify IL-6, TNF-α, and Caspase-1. Histomorphometry (AxioVision Rel. 4.6.3 software) of tissue samples was performed in order to quantify the cytokine levels. Both the oxide coatings on SS and Ti6Al4V significantly reduced cytokine production. However, the lowest cytokine levels were observed in TiO₂ groups. Cytokine content in uncoated groups was lower in Ti6Al4V than in SS, although coating of either metal reduced cytokine production to similar levels. Sol–gel TiO₂ or SiO₂ coatings reduced significantly the production of proinflammatory cytokines by local tissues, irrespective of the material used as a substrate, that is, either Ti6Al4V or SS. This suggests lower inflammatory response, which directly points out improvement of materials’ biocompatibility.