Coatings developed to reduce biofouling of engineered surfaces do not always perform as expected based on their native properties. One reason is that a relatively small number of highly adhesive sites, or the heterogeneity of the coated surface, may control the overall response of the system to initial bacterial deposition. It is shown here using an approach we call spectral force analysis (SFA), based on force volume imaging of the surface with atomic force microscopy, that the behavior of surfaces and coatings can be better understood relative to bacterial adhesion. The application of vapor deposited TiO2 metal oxide increased bacterial and colloid adhesion, but coating the surface with silica oxide reduced adhesion in a manner consistent with SFA based on analysis of the “stickiest” sites. Application of a TiO2-based paint to a surface produced a relatively non-fouling surface. Addition of a hydrophilic layer coating to this surface should have decreased fouling. However, it was observed that this coating actually increased fouling. Using SFA it was shown that the reason for the increased adhesion of bacteria and particles to the hydrophilic layer was that the surface produced by this coating was highly heterogeneous, resulting in a small number of sites that created a stickier surface. These results show that while it is important to manufacture surfaces with coatings that are relatively non-adhesive to bacteria, it is also essential that these coatings have a highly uniform surface chemistry. 相似文献
Development of anti-biofouling coating has attracted immense attention for reducing the massively detrimental effects of biofouling in systems ranging from ship hulls and surgical instruments to catheters, implants, and stents. In this paper, we propose a model to quantify the role of electrostatic and van der Waals (vdW) forces in dictating the efficacy of dielectric coating for preventing the nonspecific adhesion mediated biofouling in salty systems. The model considers a generic charged lipid-bilayer encapsulated vesicle-like structure representing the bio-organism. Also, we consider the fouling caused by the nonspecific adhesion of the bio-organism on the substrate, without accounting for the explicit structures (e.g., pili, appendages) or conditions (e.g., surface adhesins secreted by the organisms) involved in the adhesion of specific microorganism. The model is tested by considering the properties of actual coating materials and biofouling causing microorganisms (bacteria, fungi, algae). Results show that while the electrostatic-vdW effect can be significant in anti-biofouling action for cases where the salt concentration is relatively low (e.g., saline solution for surgical instruments), it might not be effective for marine environment where the salt concentration is much higher. The findings, therefore, point to a hitherto unexplored driving mechanism of anti-biofouling action of the coating. Such an identification will also enable the appropriate choices of the coating materials (e.g., possible dielectric material with volume charge) and other system parameters (e.g., salinity of the solution for storing the surgical instruments) that will significantly improve the efficiency of the coatings in preventing the nonspecific adhesion mediated biofouling. 相似文献
Enzymes cleaving the biopolymer adhesives of fouling organisms are attracting attention for the prevention of biofouling. We report a versatile and robust method to confine the serine protease Subtilisin A (or Subtilisin Carlsberg) to surfaces to be protected against biofouling. The approach consists of the covalent immobilization of the protease onto maleic anhydride copolymer thin film coatings. High‐swelling poly(ethylene‐alt‐maleic anhydride) (PEMA) copolymer layers permitted significantly higher enzyme loadings and activities than compact poly(octadecene‐alt‐maleic anhydride) (POMA) films. Substantial fractions of the immobilized, active enzyme layers were found to be conserved upon storage in deionized water for several hours. Ongoing studies explore the potentialities of the developed bioactive coatings to reduce the adhesion of various fouling organisms.
The influence of total surface energy on bacterial adhesion has been investigated intensively with the frequent conclusion that bacterial adhesion is less on low-energy surfaces. However, there are also a number of contrary findings that high-energy surfaces have a smaller biofouling tendency. Recently, it was found that the CQ ratio, which is defined as the ratio of Lifshitz-van der Waals (LW) apolar to electron donor surface-energy components of substrates, has a strong correlation to bacterial adhesion. However, the electron donor surface-energy components of substrates varied over only a very limited range. In this article, a series of Ni-P-TiO(2)-PTFE nanocomposite coatings with wide range of surface-energy components were prepared using an electroless plating technique. The bacterial adhesion and removal on the coatings were evaluated with different bacteria under both static and flow conditions. The experimental results demonstrated that there was a strong correlation between bacterial attachment (or removal) and the CQ ratio. The coatings with the lowest CQ ratio had the lowest bacterial adhesion or the highest bacterial removal, which was explained using the extented DLVO theory. 相似文献
A wide range of coatings can be produced by incorporating particles into an electrodeposit. The matrix may be a metal, conductive polymer or conductive ceramic, whereas the particle can be metallic, polymeric, ceramic or combinations of spheroidal, irregular or layered inclusions. Nanostructured, gradient, multilayer and sandwich layer deposit further widen possibilities. Electrochemical approaches to the deposition of composite coatings offer the benefits of good control over deposition rate (hence thickness), coating composition and deposit properties. Both faradaic electrodeposition and electrophoresis are usually involved. This review focuses on nanosized inclusions in a metal matrix over the last two decades. Interactions between bath composition, particle dispersion, operational variables and resultant deposit properties are poorly documented in the literature. Our understanding of the mechanism of composite deposition remains patchy, despite progress and computer models are scarce. Electrode geometry, electrolyte hydrodynamics and current distribution remain poorly treated. Markets in electronics, surface engineering, aerospace, corrosion protection and electrochemical energy conversion have been stimulated by newer uses for self-cleaning, superhydrophobic and biocompatible surfaces. Challenges to be met by further research and development are prioritised. 相似文献
We demonstrate the synthesis of 2D metal nanoparticles (MNPs)/graphene nanocomposites using small cationic surfactants as stabilizers. 2D sandwich-like MNPs/graphene nanocomposites with a uniform distribution of MNPs can be achieved via a one-pot in situ growth and reduction protocol. 相似文献
Adhesive and marine biofouling release properties of coatings containing surface-oriented perfluoroalkyl groups were investigated. These coatings were prepared by cross-linking a copolymer of 1H,1H,2H,2H-heptadecafluorodecyl acrylate and acrylic acid with a copolymer of poly(2-isopropenyl-2-oxazoline) and methyl methacrylate at different molar ratios. The relationships between contact angle, contact angle hysteresis, adhesion, and marine biofouling were studied. Adhesion was determined by peel tests using pressure-sensitive adhesives. The chemical nature of the surfaces was studied by using X-ray photoelectron spectroscopy. Resistance to marine biofouling of an optimized coating was studied by immersion in seawater and compared to previous, less optimized coatings. The adhesive release properties of the coatings did not correlate well with the surface energies of the coatings estimated from the static and advancing contact angles nor with the amount of fluorine present on the surface. The adhesive properties of the surfaces, however, show a correlation with water receding contact angles and contact angle hysteresis (or wetting hysteresis) resulting from surface penetration and surface reconstruction. Coatings having the best release properties had both the highest cross-link density and the lowest contact angle hysteresis. An optimized coating exhibited unprecedented resistance to marine biofouling. Water contact angle hysteresis appears to correlate with marine biofouling resistance. 相似文献
The application of nanomaterials has gained considerable momentum in various fields in recent years due to their high reactivity, excellent surface properties and quantum effects in the nanometer range. The properties of zinc oxide (ZnO) vary with its crystallite size or particle size and often nanocrystalline ZnO is seen to exhibit superior physical and chemical properties due to their higher surface area and modified electronic structure. ZnO nanoparticles are reported to exhibit strong bacterial inhibiting activity and silver (Ag) has been extensively used for its antimicrobial properties since ages. In this study, Ag doped ZnO nanoparticles were synthesized by mechanochemical processing in a high energy ball mill and investigated for antimicrobial activity. The nanocrystalline nature of zinc oxide was established by X-ray diffraction (XRD) studies. It is seen from the XRD data obtained from the samples, that crystallite size of the zinc oxide nanoparticles is seen to decrease with increasing Ag addition. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) data also supported the nanoparticle formation during the synthesis. The doped nanoparticles were subjected to antimicrobial investigation and found that both increase in Ag content and decrease in particle size contributed significantly towards antimicrobial efficiency. It was also observed that Ag doped ZnO nanoparticles possess enhanced antimicrobial potential than that of virgin ZnO against the studied microorganisms of Escherichia coli and Staphylococcus aureus. 相似文献
Antifouling coatings are used to improve the speed and energy efficiency of ships by preventing or- ganisms, such as barnacles and weed, building up on the underwater hull and helping the ships movement through the water. Typically, marine coatings are tributyltin self-polishing copolymer paints containing toxic molecules called biocides. They have been the most successful in combating bio- fouling on ships, but their widespread use has caused severe pollution in the marine ecosystem. The low surface energy marine coating is an entirely non-toxic alternative, which reduces the adhesion strength of marine organisms, facilitating their hydrodynamic removal at high speeds. In this paper, the novel low surface energy non-toxic marine antifouling coatings were prepared with modified acrylic resin, nano-SiO2, and other pigments. The effects of nano-SiO2 on the surface structure and elastic modulus of coating films have been studied, and the seawater test has been carried out in the Dalian Bay. The results showed that micro-nano layered structures on the coating films and the lowest surface energy and elastic modulus could be obtained when an appropriate mass ratio of resin, nano-SiO2, and other pigments in coatings approached. The seawater exposure test has shown that the lower the sur- face energy and elastic modulus of coatings are, the less the marine biofouling adheres on the coating films. 相似文献
Metal nanoparticles (MNPs) with a small diameter and narrow size distribution can be prepared by H(2) reduction of metal compounds or decomposition of organometallic species dissolved in ionic liquids (ILs). MNPs dispersed in ILs are catalysts for reactions under multiphase conditions. These soluble MNPs possess a pronounced surfacelike rather than single-site like catalytic properties. In other cases the MNPs are not stable and tend to aggregate or serve as reservoirs of mononuclear catalytically active species. 相似文献
Bacterial attachment is an initial stage in biofilm formation that leads to flux decline in membrane water filtration. This study compares bacterial attachment among three photocatalytic ceramic ultrafiltration membranes for the prevention of biofilm formation. Zirconia ceramic ultrafiltration membranes were dip-coated with anatase and mixed phase titanium dioxide photocatalysts to prevent biofilm growth. The membrane surface was characterized in terms of roughness, hydrophobicity, bacterial cell adhesion, and attached cell viability, all of which are important factors in biofilm formation. The titanium dioxide coatings had minimal impact on the membrane roughness, reduced the hydrophobicity of membranes, prevented Pseudomonas putida attachment, and reduced P. putida viability. Degussa P25 is a particularly promising reactive coating because of its ease of preparation, diminished cell attachment and viability in solutions with low and high organic carbon concentrations, and reduced flux decline. These reactive membranes offer a promising strategy for fouling resistance in water filtration systems. 相似文献
The present work shows the feasibility of preparing transparent titania coatings being doped with platinum nanoparticles by sol–gel processing. The used platinum nanoparticles are modified by two different functional thiol ligands, mercaptoethanol and mercaptopropionic acid. The functional ligands are used to create a nanoparticle network and they can also promote anchorage of titanium alkoxides as sol–gel precursors, ensuring a regular distribution of the metal nanoparticles within the coating as well as a good stability to the film. 相似文献
An investigation into the hemo‐biocompatibility of calix[4]resorcinarenetetrathiol and calix‐PEG derivative coatings on gold electrodes is reported, with respect to the detection of the ascorbate ion in aqueous solution. The electrochemical behavior of the ascorbate ion at calix‐modified electrodes is also discussed. Findings show that a facilitated adsorption of ascorbate from solution is seen at calix‐modified gold electrodes. Following exposure to whole human blood, calix‐PEG derivative coatings were seen to offer some protection against both outer‐surface biofouling and electrode passivation effects in comparison to calix[4]resorcinarenetetrathiol counterparts. The individual effects of outer surface biofouling and electrode passivation on exposure to whole blood have been investigated. Our findings suggest that PEG moieties help prevent sorption of the biofouling film, thus possibly minimizing the release of a number of low molecular weight solutes which are thought to be involved with the passivation of electrode responses within clinical bio‐ and chemical sensors. 相似文献
A colorimetric method for quantification of galactose, which utilizes a nanostructured multi-catalyst system consisting of Fe(3)O(4) magnetic nanoparticles (MNPs) and galactose oxidase (Gal Ox) simultaneously entrapped in large pore sized mesocellular silica, is described. Gal Ox, immobilized in a silica matrix, promotes reaction of galactose to generate H(2)O(2) that subsequently activates MNPs in silica mesopores to convert a colorimetric substrate into a colored product. By using this colorimetric method, galactose can be specifically detected. Along with excellent reusability via application of simple magnetic capturing, enhanced operational stability was achieved by employing a cross-linked enzyme aggregate (CLEA) method for Gal Ox immobilization. This protocol leads to effective prevention of enzyme leaching from the pores of mesocellular silica. The analytical utility of the new colorimetric biosensor was demonstrated by its use in diagnosing galactosemia, a genetic metabolic disorder characterized by the inability to utilize galactose, through analysis of clinical dried blood spot specimens. A microscale well-plate format was employed that possesses a multiplexing capability. The multi-catalyst system entrapping Gal Ox and MNPs represents a new approach for rapid, convenient, and cost-effective quantification of galactose in human blood and it holds promise as an alternative method for galactosemia diagnosis, replacing the laborious procedures that are currently in use. 相似文献