N,N-diethyl-N-(2-methancryloylethy)-N-methylammonium bis(trifluoromethylsulfonyl) imide polymer (DEMM-TFSI) brush coated specimens (substrate: glasses) and a liquid ion type of polymer brush coating were investigated for their antifouling effect on biofilms. Biofilms were produced by two kinds of bacteria, E. coli and S. epidermidis. They were formed on specimens immersed into wells (of 12-well plates) that were filled with culture liquids and bacteria. The biofilm formation was observed. Also, brush coated specimens and glass substrates were investigated in the same way. DEMM polymer brush coated specimens formed more biofilm than PMMA (polymethyl methacrylate) polymer brush coated specimens and glass substrates. A greater amount of polarized components of biofilms was also observed for DEMM polymer brush coated specimens. The polar characteristics could be attributed to the attraction capability of bacteria and biofilms on DEMM polymer brush coated specimens. When considering the ease of removing biofilms by washing it with water, the ionic liquid type polymer brush (coated specimens) could be used for antifouling applications. If an initial antifouling application is needed, then the polar characteristics could be adjusted (design of the components and concentrations of ionic liquids, etc.) to solve the problem.
A type of polymer brush, made from an ionic liquid, was prepared and used to investigate the behavior and tendency of biofilm formation. The polymer brush specimens were immersed into the wells of microtiter plates filled with culture liquids containing bacteria. Two different combinations of bacteria and liquid cultures were used for this experiment. One was LB liquid medium with E-coli and the other was Heart Infusion liquid medium with S.epidermidis. After the specimens were immersed for a certain amount of time, they were removed from the test wells and evaluated for biofilm formation. The evaluation methods used were Raman Spectroscopy and crystal violet staining. Polymer brush specimens generally showed biofilm formations for specimens tested in both bacterial cases. However, both of these biofilms could be removed, when the specimens were immersed in water for a couple of hours. Probably the use of special polymer brushes will be valuable in the future, for controlling biofilm and related contaminants on a variety of materials and components.
The polymer brush generally has high water repellency, adhesion, durability and antifouling properties. As for the last characteristics, it often works well to clean materials’ surfaces. Since it displays the lotus effect, it repels water. This water (which rolls off of the surface) picks up and carries away contaminants. What about its effect for biofilm? In this study, we seek the answer by using a polymer brush formed on glass. Biofilms are produced by bacterial activities. Usually, bacteria attach to tissues in human bodies, and also to solid materials, since organic compounds (which serve as their nutrition) exist there. When the number of bacteria attached to these interfaces increases and reaches the threshold value, then exopolymeric substances are excreted from their cells. Therefore bacteria on materials’ surfaces are surrounded by sticky water including various kinds of organic polymers (exopolymeric substances: EPS). At this point, biofilms form on materials. Generally speaking, bacteria in biofilms have a high tolerance against biocides and antibiotics. This means that biomaterials should have high anti-biofilm formation capabilities. The application of a polymer brush to the surface finishing of biomaterials may serve as a countermeasure to protect biomaterials against biofilm formation. In this study, a polymer brush was formed on glass specimens by living radical polymerization of ionic liquids (N,N-diethyl-N-(2-methacryloylethyl)-N-methylammonium bis imide(DEMM-TFSI). Also their inhibition effects against biofilm formation were investigated. The biofilm evaluation system was mainly composed of artificial biofilm production and various evaluation processes. In this study, the artificial biofilm formation was carried out by two different processes. One was a static process where specimens were placed in plastic wells filled with liquid cultures (LB and HI cultures) with and without bacteria (E.coli and S. epidermidis, respectively). The other was the process using a flow type Laboratory Biofilm Reactor (LBR). The specimen was suspended in a reservoir and fixed by a jig. And the same culture liquids, including bacteria in the reservoir, flowed by using a rotating stirrer. After a certain amount of time (a couple of days), each sample was taken out of the system and the specimen’s surface was observed by Raman spectroscopy and stained by crystal violet (0.1%) to check the extent of biofilm formation. The results were analyzed, compared, and discussed qualitatively and quantitatively. We confirmed that the polymer brush tended to control biofilm formation. The mechanism was considered in the following two ways. One of them would be the Lotus effect where the surface profile of a polymer brush might work well (Lotus effect). The other one was the antibacterial and anti-biofilm effects by ionic liquids. In this case, ionic liquid as a raw material was almost completely fixed and insoluble. However, a very small amount might dissolve at the tip of polymer brush.
Biofilms are formed on materials surfaces by bacterial activities, which leads to the many kinds of contaminations and causes many industrial problems such as scale inside cooling water pipes, corrosion, hygiene issues at kitchens, dining, toilets, bath tubs, chronic diseases in medical fronts etc. To solve the industrial problems, many countermeasures have been proposed so far. The approach from the viewpoint of materials is one of the good ways to solve the biofilm problems. In this research, we investigated how biofilm behaviors formed in a flow type laboratory biofilm reactor (Fig.1) were affected by polymer brush coating of ionic liquids. As polymer brush, N-diethyl-N-(2-methacryloylethyl)-N-methylammonium bis(trifluoromethylsulfonyl) imide (ρDEMM-TFSI) was used with PMMA polymer brush coating as control. The polymer brush coated glass specimens were immersed in the laboratory biofilm reactor where environmental bacteria were mixed into water to form biofilms in the reactor. The specimens with biofilms were evaluated by Raman spectroscopy and optical microscopic observations. And the results were compared with those for PMMA polymer brush specimens. The results were also compared with those obtained by static immersion tests. As well as the results by static methods, ρDEMM-TFSI polymer coating specimens were sensitive to biofilm formation, being compared with the results for PMMA polymer brush coating specimens. The reason could be attributed to the ionic (anionic )polarization of ρDEMM-TFSI coating’s surfaces. However, those biofilms seemed to be concentrated at the vicinity of surfaces. Therefore, the biofilms restricted to the surface area might be removed easily. Figure 1
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