Katsuhiko Sano

Composite coating to control biofilm formation and effect of alternate electro-magnetic field

Abstract Three kinds of composite coating (the common matrix was silane oligomer and titanium organic, tin organic and nickel organic compounds were dispersed in the matrices) specimens on glasses were immersed in a unique Laboratory Biofilm Reacter (LBR) for 12 days. In the LBR, the water was circulated, incorporating ambient germs into the system and biofilm was formed on the specimen set in the LBR. In the LBR, clean water was circulated and the weak alternative electromagnetic field was applied to the water phase. For the biofilm resistant coating (organic titanium or tin composite coating based on silane oligomer), the effect of the applied alternative electromagnetic field was remarkable.

Application of bacterial 16S rRNA gene analysis to a comparison of the degree of biofilm formation on the surface of metal coated glasses

Abstract The contaminated surfaces of materials are generally covered with a biofilm that consists of microorganisms and extracellular polysaccharides. The Gram stain method, which is used to visualise bacteria, allows biofilms to be semiquantitatively analysed. Although this method can be used to compare the amount of bacteria in a biofilm, we cannot identify kinds of bacteria. In the present study, 16S rRNA gene analysis was performed to measure and determine the bacterial population in biofilms formed on organic nickel coated glass and uncoated glass. The amount of 16S rRNA was markedly higher on organic nickel coated glass than on uncoated glass. 16S rRNA sequencing revealed that the majority of bacteria on uncoated glass and organic nickel coated glass were Proteobacteria, especially Sphingomonadales and Methylophilales; however, a marked difference was observed in the amount of Sphingomonadales on these glasses.

Corrosion and biofilm for a composite coated iron observed by FTIR-ATR and Raman spectroscopy

Corrosion of metallic materials occurs in various ways. Recently, many researchers have pointed out that biofilm formed by a biofouling process may be a main cause for the initial stage of corrosion. From this viewpoint, the control of biofilm would help lead to corrosion prevention. In this paper, the authors studied the composite film of silane compounds with dispersed organometallic compounds that showed anti-fouling effect on pure iron substrates. The specimens were immersed in a laboratory biofilm reactor for 7 days to form biofilms on them. The surfaces of the specimens were observed by optical and scanning electron microscopy, Raman spectroscopy and FTIR-ATR spectroscopy. Finally, the effect of the composite coating on biofilm formation and corrosion characteristics was studied and shown to inhibit both.

Overview of Silane-Based Polymer Coatings and Their Applications

Silane resin coatings, their structure, characteristics, and applications are reviewed. Generally, silane compounds are classified into two types, silicone and silicates, and make up organic paints and coating agents that are easy to handle and inexpensive and have high designing capability. However, they are vulnerable to ultraviolet light and heat due to the carbon–carbon bonds which also accounts for their lack of durability. Therefore, the authors herein have developed and investigated the applicability of alkoxysilane compounds for coatings and painting films. Conventionally, the mechanical strength and adhesion force to the substrate have not been good for silane polymer resins. However, the newly investigated and developed alkoxysilane compound films could solve these conventional problems. The concepts of the novel silane compound films and the rational for the research and development will be described. Further, the application possibilities in many industrial fields will be introduced in this chapter, with concrete examples mentioned.

Effect of Silver or Copper Nanoparticles-Dispersed Silane Coatings on Biofilm Formation in Cooling Water Systems

Biofouling often occurs in cooling water systems, resulting in the reduction of heat exchange efficiency and corrosion of the cooling pipes, which raises the running costs. Therefore, controlling biofouling is very important. To regulate biofouling, we focus on the formation of biofilm, which is the early step of biofouling. In this study, we investigated whether silver or copper nanoparticles-dispersed silane coatings inhibited biofilm formation in cooling systems. We developed a closed laboratory biofilm reactor as a model of a cooling pipe and used seawater as a model for cooling water. Silver or copper nanoparticles-dispersed silane coating (Ag coating and Cu coating) coupons were soaked in seawater, and the seawater was circulated in the laboratory biofilm reactor for several days to create biofilms. Three-dimensional images of the surface showed that sea-island-like structures were formed on silane coatings and low concentration Cu coating, whereas nothing was formed on high concentration Cu coatings and low concentration Ag coating. The sea-island-like structures were analyzed by Raman spectroscopy to estimate the components of the biofilm. We found that both the Cu coating and Ag coating were effective methods to inhibit biofilm formation in cooling pipes.

Microbiome Analysis of Biofilms of Silver Nanoparticle-Dispersed Silane-Based Coated Carbon Steel Using a Next-Generation Sequencing Technique

Previously, we demonstrated that silver nanoparticle-dispersed silane-based coating could inhibit biofilm formation in conditions where seawater was used as a bacterial source and circulated in a closed laboratory biofilm reactor. However, it is still unclear whether the microbiome of a biofilm of silver nanoparticle-dispersed silane-based coating samples (Ag) differs from that of a biofilm of non-dispersed silane-based coating samples (Non-Ag). This study aimed to perform a microbiome analysis of the biofilms grown on the aforementioned coatings using a next-generation sequencing (NGS) technique. For this, a biofilm formation test was conducted by allowing seawater to flow through a closed laboratory biofilm reactor; subsequently, DNAs extracted from the biofilms of Ag and Non-Ag were used to prepare 16S rRNA amplicon libraries to analyze the microbiomes by NGS. Results of the operational taxonomy unit indicated that the biofilms of Non-Ag and Ag comprised one and no phyla of archaea, respectively, whereas Proteobacteria was the dominant phylum for both biofilms. Additionally, in both biofilms, Non-Ag and Ag, Marinomonas was the primary bacterial group involved in early stage biofilm formation, whereas Anaerospora was primarily involved in late-stage biofilm formation. These results indicate that silver nanoparticles will be unrelated to the bacterial composition of biofilms on the surface of silane-based coatings, while they control biofilm formation there.

Nickel, molybdenum, and tungsten nanoparticle-dispersed alkylalkoxysilane polymer for biomaterial coating: evaluation of effects on bacterial biofilm formation and biosafety

Biofilm formation on the surfaces of biomaterials can cause severe infectious diseases due to of inefficiency of antibiotics against biofilm-protected pathogens. On one hand, the prevention of biofilm formation is a critical issue in the development of biomaterials. On the other hand, biomaterials require biological compatibility. To achieve these two goals without compromising the original features of the biomaterial, we proposed metal nanoparticle (NP)-dispersed alkylalkoxysilane (AAS) coatings. Here, we chose nickel, molybdenum, and tungsten, components of stainless steel and other alloys for biomaterials, as prospective metals that could regulate biofilm formation without harming human health. To the best of our knowledge, this is the first report to describe the effect of tungsten on biofilm formation. We performed a biofilm formation test using an open laboratory biofilm reactor that utilizes tap water and environmental bacteria from the laboratory air, and we also performed a cytotoxicity test on the human monocyte-derived U937 cell line. Compared with the AAS polymer alone, nickel NP-dispersed AAS polymer exhibited an inhibitory activity against biofilm formation whereas tungsten and molybdenum NP-dispersed AAS polymers facilitated biofilm formation. The effect of tungsten was dose-dependent. At a low metal concentration (0.1 mol%), the NP-dispersed AAS polymers did not affect cell survival. These results showed that for nickel, molybdenum, and tungsten, the NP-dispersed AAS polymers exhibited biosafety and that the nickel NP-dispersed AAS polymer is suitable for inhibiting biofilm formation. To determine whether molybdenum (or tungsten) NP-dispersed AAS polymer is suitable for biomaterial application, further evaluation in an environment that mimics the human body with clinically relevant pathogens is necessary. Correspondence to: Akiko Ogawa, Department of Chemistry and Biochemistry, National Institute of Technology, Suzuka College, Suzuka 510-0294, Japan, Tel: +81-59-368-1768; E-mail: ogawa@chem.suzuka-ct.ac.jp