Antibacterial Properties Of Coatings Research Articles

Antibacterial Calcium Phosphate Coatings for Biomedical Applications Fabricated via Micro-Arc Oxidation.

A promising method for improving the functional properties of calcium-phosphate coatings is the incorporation of various antibacterial additives into their structure. The microbial contamination of a superficial wound is inevitable, even if the rules of asepsis and antisepsis are optimally applied. One of the main problems is that bacteria often become resistant to antibiotics over time. However, this does not apply to certain elements, chemical compounds and drugs with antimicrobial properties. In this study, the fabrication and properties of zinc-containing calcium-phosphate coatings that were formed via micro-arc oxidation from three different electrolyte solutions are investigated. The first electrolyte is based on calcium oxide, the second on hydroxyapatite and the third on calcium acetate. By adding zinc oxide to the three electrolyte solutions, antibacterial properties of the coatings are achieved. Although the same amount of zinc oxide has been added to each electrolyte solution, the zinc concentration in the coatings obtained vary greatly. Furthermore, this study investigates the morphology, structure and chemical composition of the coatings. The antibacterial properties of the zinc-containing coatings were tested toward three strains of bacteria-Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. Coatings of calcium acetate and zinc oxide contained the highest amount of zinc and displayed the highest zinc release. Moreover, coatings containing hydroxyapatite and zinc oxide show the highest antibacterial activity toward Pseudomonas aeruginosa, and coatings containing calcium acetate and zinc oxide show the highest antibacterial activities toward Staphylococcus aureus and methicillin-resistant Staphylococcus aureus.

Incorporation of ZnO–ZrO2 nanoparticles into TiO2 coatings obtained by PEO on Ti–6Al–4V substrate and evaluation of its corrosion behavior, microstructural and antibacterial effects exposed to SBF solution

In this research, Plasma Electrolytic Oxidation technique was used to incorporate ZnO–ZrO2 nanoparticles into TiO2 ceramic coating on Ti6–Al–4V using sodium phosphate as an electrolyte. The effect of adding these nanoparticles on corrosion, morphology, wettability and antibacterial properties in the simulated body fluid (SBF) solution was investigated. The results indicated nanoparticles modified the microstructure of coating, which increased corrosion resistance 12 times higher than that of substrate. Besides, ZrO2 nanoparticles had the most significant effect on increasing the contact angle. In addition, due to the compatibility of zirconium and zinc oxides with human body environment, the antibacterial properties of coatings were significantly improved.

The effect of gas flow rate on structural, mechanical and antibacterial properties of atmospheric plasma sprayed Cu coatings

The Copper (Cu) powder is sprayed on 316L stainless steel surface using an atmospheric plasma spray (APS) system to eliminate infections and bacteria on the surface. Here, the effects of gas flow rate (GFR) on structural, mechanical and antibacterial properties of coatings are investigated. The comparative analysis of coatings created by different gas flow rates of 20, 25, 30 and 35 lmin−1 is performed. The results show that the coating with 20 lmin−1 GFR is thin and too weak due to the disturbance in the thermal pinch and the existing excessive pores. With increasing the GFR, the coating roughness and porosity decrease which in turn increases the hardness and adhesion of the coatings. The connection between flat splats and continuous and uniform layers gets better. The high-quality coating is seen at the GFR of 30 lmin−1 with the adhesion strength and hardness of 4B and 163 HV0.1, respectively. Besides, it shows three and a half and three times increase of antibacterial property after 12 h compared to 316L stainless steel versus PTCC 1112 Staphylococcus aureus and ATCC 10536 Escherichia coli bacteria, respectively. But the coating having a GFR higher than critical value (30 lmin−1) shows discontinuous layers due to the plasma jet divergence and reduction of particles velocity.

Corrosion of an Active Antibacterial Nanostructured Coating on Titanium

This study aims on antibacterial and corrosion characterization of a complex ceramic coating based on titania (TiO2) nanotubes, hydroxyapatite (HA) and single walled carbon nanotubes (SWCNTs), in physiological environment. Hybrid materials structure was identified by Fourier transformed infrared spectroscopy (FTIR) and their surface analysed by scanning electron microscopy (SEM) and contact angle analysis. The most hydrophilic sample was the one with TiO2-HA coating. The electrochemical behavior of materials has been investigated in Ringer solution performing potentiodiynamic polarization and electrochemical impedance spectroscopy. Antibacterial properties of coatings were determined by contact method using two types of strains, one of them Staphylococus aureus (S. aureus) is a positive gram bacteria and another one Pseudomonas aureoginosa (P. aureoginosa) a negative gram bacteria. The corrosion rates are in the perfect stable domain of corrosion resistance and no breakdown phenomena were observed. A range of stability in tested bioliquid has been established from electrochemical and ICP-MS measurements. TiO2-HA-SWCNTs coating has the best corrosion resistance and the best barrier properties for ions release. Antibacterial effect of TiO2-HA-SWCNTs coating seems to be synergistic being higher compared to TiO2 nanotubes and TiO2-HA coating.

Antibacterial characteristics of thermal plasma spray system.

The objective of this study is to investigate antibacterial characteristics of a thermal plasma spray system. For this purpose, copper powder was coated on a handmade atmospheric plasma spraying system made by the stainless steel 316 substrate, which is preheated at different temperatures before spraying. A number of deposition characteristics such as antibacterial characteristics, adhesion strength and hardness of coating, was investigated. All of the spray parameters are fixed except the substrate temperature. The chemical composition was analyzed by X-ray diffraction (XRD). A scanning electron microscopy (SEM) and back scattering electron microscopy (BSE) were used to show the coating microstructure, its thickness and also the powder micrograph. The energy dispersive X-ray spectroscopy (EDX) was used to analyze the coating particles. Hardness of the deposition was examined by Vickers tester (HV0.1). Its adhesion strength was declared by cross cut tester (TQC). In addition, the percentage of bactericidal coating was evidenced with Staphylococcus aurous and Escherichia coli bacteria. Study results show that as the substrates temperature increases, the number of splats in the shape of pancake increases, the greatness and percentage of the deposition porosity both decrease. The increment of the substrate temperature leads to more oxidation and makes thicker dendrites on the splat. The enhancement of the substrate temperature also enlarges thickness and efficiency of coating. The interesting results are that antibacterial properties of coatings against the Escherichia coli are more than Staphylococcus aurous bacteria. However the bactericidal percentage of the coatings against Staphylococcus aurous and Escherichia coli bacteria roughly does not change with increasing the substrate temperature. Furthermore, by increment of the substrate temperature, coatings with both high adhesion and hardness are obtained. Accordingly, the temperature of substrate can be an important parameter for progressing mechanical properties of the antiseptic deposition.

Morphologic, Photocatalytic and Antibacterial Properties of ZnO-TiO<sub>2</sub> Sol-Gel System

Prepared and heat-treated sol-gel ZnO-TiO2 coatings onto microscope glass slides were characterised by atomic force microscopy (AFM), scanning electron microscopy (SEM), as well as absorption spectra of light has been obtained. Thermally treated xerogels were characterised by X-ray diffraction (XRD). As well as their photocatalytic activity using methyl orange (MO) and observing the colour changes over the time in visible light (VIS) and ultra violet (UV) light has been determined. The influence of ZnO concentration on morphology, photocatalytic activity and antibacterial properties of coatings was analysed. The growth of S. epidermidis on the surface of the samples was inhibited due to photocatalytic properties of coatings.

Preparation of modified nano ZnO/polyester/TGIC powder coating nanocomposite and evaluation of its antibacterial activity

Powder coating nanocomposite with antibacterial properties is the aim of this study. For this purpose, nano zinc oxide was modified by vinyltrimethoxysilane (VTMS) and Triethoxy(methyl)silane (TEMS). Then various percentages of modified and non-modified nano ZnO (1, 3 and 5%), polyester resin and triglycidyl isocyanurate as a hardener were blended by twin screw extruder. Prepared polymer–matrix composite (PMC) was atomized and coated by electrostatic method on aluminum plates. Finally, samples were cured for 10 min at 200 °C. For investigating the thermal stabilities of modified nano particles, thermogravimetric analyses (TGA) were used. Antibacterial properties of coatings were investigated by gram negative bacteria Escherichia coli and gram positive Staphylococcus aureus. The results showed that the coatings demonstrate significant antibacterial activity by increasing amounts of ZnO nanoparticles (5%) when were modified by VTMS.

Alternating current electrophoretic deposition of antibacterial bioactive glass-chitosan composite coatings.

Alternating current (AC) electrophoretic deposition (EPD) was used to produce multifunctional composite coatings combining bioactive glass (BG) particles and chitosan. BG particles of two different sizes were used, i.e., 2 μm and 20–80 nm in average diameter. The parameter optimization and characterization of the coatings was conducted by visual inspection and by adhesion strength tests. The optimized coatings were investigated in terms of their hydroxyapatite (HA) forming ability in simulated body fluid (SBF) for up to 21 days. Fourier transform infrared (FTIR) spectroscopy results showed the successful HA formation on the coatings after 21 days. The first investigations were conducted on planar stainless steel sheets. In addition, scaffolds made from a TiAl4V6 alloy were considered to show the feasibility of coating of three dimensional structures by EPD. Because both BG and chitosan are antibacterial materials, the antibacterial properties of the as-produced coatings were investigated using E. coli bacteria cells. It was shown that the BG particle size has a strong influence on the antibacterial properties of the coatings.

Antibacterial properties of TiO2–Cu composite thin films grown by a one step DLICVD process

The correlations between microstructural features, chemical compositions and antibacterial properties of coatings containing metallic Cu particles embedded in a titanium dioxide matrix have been determined. A Direct Liquid Injection Chemical Vapor Deposition (DLICVD) process was used for the one step growth of TiO2–Cu composite coatings on various substrates. Titanium tetra-iso-propoxide (TTIP) and copper bis(2,2,6,6-tetramethyl-3,5-heptationate) (Cu(tmhd)2) were used as titanium and copper molecular sources, respectively. This growth process allows a good control of the quantity of metalorganic precursors injected into the CVD reactor and thus of the coating composition. The deposition occurs at 683K under low pressure (800Pa). The influence of the main features of the coatings on their antibacterial properties was investigated in order to produce bactericidal surfaces that are durable, non-toxic and containing a minimum amount of active agent. The antibacterial activity on Staphylococcus aureus without any photon activation was measured according to the JIS Z 2801:2000 standard method. An antibacterial activity was detected for a low metal content of ca. 1at.% Cu, and was found to increase with the Cu content. It was maximal for 3.5at.% Cu, i.e. TiO2–Cu composite coatings exhibit bactericidal behavior against S. aureus for this optimal composition (relative activity=100%). In order to better characterize the microbiological behavior of the coatings more discriminating methods derived from the literature were tested to assess the performances of these CVD coatings in terms of efficiency, release of antibacterial agent and accelerated aging.

Single-step fabrication of non-leaching antibacterial surfaces using vapor crosslinking

We report the fabrication of non-leaching antibacterial surfaces using a single-step vapor crosslinking method. Vapors of dimethylaminomethylstyrene (DMAMS) and ethylene glycol diacrylate (EGDA) were copolymerized to produce crosslinked polymer coatings conformally on both planar and porous substrates. The antibacterial properties of coatings with systematically controlled crosslinked degrees were studied. The crosslinked coatings kill bacteria through disruption of the bacteria membrane upon surface contact. Bacteria reduction rates as high as 99.99% were achieved against both Gram-positive Bacillus subtilis and Gram-negative Escherichia coli. The strong antibacterial activity of the highly crosslinked coatings indicates that the mobility and length of antibacterial polymer chains are not critical in determining the bactericidal activity of the P(DMAMS-co-EGDA) coatings. Leaching tests demonstrated that the P(DMAMS-co-EGDA) coatings did not leach from the surface and were stable after the durability tests.

Anti-bacterial and cytotoxic properties of plasma sprayed silver-containing HA coatings

Silver-containing hydroxyapatite (HA) coatings have been prepared on titanium substrate by vacuum plasma spraying (VPS) method and anti-bacterial properties of the coatings were examined. Three types of bacteria stains, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, were employed in this test. The results showed that the silver-containing HA coatings exhibited significant anti-bacterial effects against the three bacteria with anti-bacterial ratios higher than 95%. The release of silver ions in the physiological environment ensured excellent anti-bacterial properties of the silver-containing HA coatings. International standard ISO 10993-12 was adopted for cytotoxicity evaluation using fibroblast cell line L929, and it was found that the cytotoxicity for the coatings ranked 0 that showed no cytotoxicity for the coatings. Hemolysis test was processed according to ASTM F 756 standard with anti-coagulated rabbit blood, and the hemolysis ratios of the coatings were below 0.4%, indicating of non-hemolysis for the coatings.