The effect of covalent surface immobilization on the bactericidal efficacy of a quaternary ammonium compound

This study investigates the effect of surface immobilization on the bactericidal function of a quaternary ammonium compound. Quaternary ammonium silane (QAS) coated planar surfaces did not produce any measurable mortality of Staphylococcus aureus, while 1 µm QAS‐coated microparticles did produce S. aureus mortality. The experiments using QAS‐coated microparticles indicate that the ability of QAS molecules to disrupt the cell wall is not hindered by covalent immobilization of QAS to a surface. These results provide evidence that S. aureus cells on a QAS‐coated planar surface are not exposed to a sufficient number of QAS molecules to produce significant mortality. This result has important implications for the development of self‐decontaminating coatings. Covalent immobilization is used to prevent leaching of the bactericidal compound. However, covalent immobilization may result in a significant tradeoff in bactericidal performance. Published in 2007 by John Wiley & Sons, Ltd.     

Preparation and antibacterial activity of hybrid materials containing quaternary ammonium salts via sol-gel process

Organic-inorganic hybrid coatings containing quaternary ammonium salts (QAS) bonded to the organic-inorganic network were prepared from tetraethoxysilane and triethoxysilane terminated poly(ethylene glycol)-block-poly(ethylene) using a sol-gel process. They were applied as a thin layer (0.6-1 μm) to PE films and the antibacterial activity of the coated films was tested against both Gram-negative (Escherichia coli ATCC 25922) and Gram-positive (Staphylococcus aureus ATCC 6538) bacteria. Measurements at different contact times showed a rapid decrease of the viable count for both the tested strains. In particular, after 48 h of contact, a decrease of 96.4% and 99.1% of E. coli and S. aureus, respectively, was observed. The permanence of the antibacterial activity of the coated films was demonstrated through repeated washings and prolonged immersion in physiological saline solutions at 37 °C. Indeed, due to the removal of QAS moieties by the nucleophilic attack of water, the antibacterial activity after 24 h was strongly reduced when measured on samples submitted to several washings. However, a quite good antibacterial activity was observed even on the same samples after 96 h, probably due to a spontaneous partial restoring of the QAS on the surface. Very good transparency, quite good adhesion and high wettability are further features of these hybrid coatings.     

Preparation and characterization of polyurethane based self-cleaning and antibacterial coating containing silver ion exchanged montmorillonite/TiO<Subscript>2</Subscript> nanocomposite

In order to reach an antibacterial, photocatalytic, and hydrophilic coating, commercial grade polyurethane (CPU) resin was modified with silver ion exchanged montmorillonite/TiO₂ nanocomposite in various montmorillonite to TiO₂ nanoparticle ratios. To characterize the prepared nanocomposites and coatings, X-ray diffraction patterns, FTIR and UV–Vis spectroscopy and SEM images were used. The modified commercial grade polyurethane coatings containing nanocomposites show better properties, including hydrophilicity, degradation of organic pollutants, antibacterial activity and water resistivity, compared to unmodified commercial grade polyurethane coatings. The water droplet contact angle of unmodified CPU coating was 70°, however it decreased to lower than 10° in modified CPU coatings after 24 h LED lamp irradiation. Decolorization efficiency of malachite green dye solution by the use of modified CPU coatings achieved up to 70% after 5 h LED lamp illumination, compared to less than 5% for unmodified CPU coatings. Modified CPU coatings also showed significant water resistivity and antibacterial properties.     

Preparation and Antibacterial Function of Quaternary Ammonium Salts Grafted Cellulose Fiber Initiated by Fe2 +-H2O2 Redox

The surface contact disinfecting technique is a newly developed method for water sterilization. In this paper, the grafted quaternary ammonium salts (QAS) antibacterial fibers were prepared and designed to apply for the surface contact disinfecting process in water treatment. The antibacterial fibers were directly prepared by grafting methacryloxylethyl benzyl dimethyl ammonium chloride (DMAE-BC) onto cellulose fiber using thiocarbonate-H₂O₂ redox system. All kinds of factors in the grafting reactions, such as reaction time, reaction temperature, monomer concentration, initiator concentration, which influence the percentage of grafting, were studied and optimized. The modified cellulose fibers were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope(SEM). The effects of the percentage of grafting of the grafted cellulose fibers on bactericidal activity were also studied. The spread plate method was used to characterize the bactericidal activity. The disinfection process was further investigated by directly observing the morphology of the bacterial cells adsorbed on the antibacterial fibers with SEM and measuring extracelluar total protein concentration in suspension. The poly(DMAE-BC)-grafted cellulose ?ber was found to exhibit particularly high activity against E.coli.     

Antibacterial photocatalytic self‐cleaning poly(vinylidene fluoride) membrane for dye wastewater treatment

Membrane technology has been successfully applied for the removal of dyes from wastewater in the textile industry. A novel poly(vinylidene fluoride) (PVDF) membrane was prepared via blending with different dosages of Ag‐TiO₂‐APTES composite for dyeing waste water treatment in our study. And the effect of Ag‐TiO₂‐APTES blended into the PVDF membrane was discussed, including the rejection rate of methylene blue (MB) dye, membrane morphology, surface hydrophilicity, antibacterial activity, and a certain photocatalytic self‐cleaning performance. X‐ray diffraction and Fourier transform infrared characterization confirmed that Ag‐TiO₂ was functionalized by amount of hydroxyl group (−OH) and amino group (NH−), which provided by APTES. Contact angle measurement certified that the hydrophilicity of the membrane surface increased, with the contact angle decrease to 61.4° compared with 81.8° of original PVDF membrane. MB rejection rate was also increased to 90.1% after addition of Ag‐TiO₂‐APTES, and the rejection of original membrane was only 74.3%. The morphologies of membranes were observed by scanning electron microscope, which indicated that Ag‐TiO₂‐APTES had a good dispersion in membrane matrix and also improved the microstructure of membranes. Besides, UV irradiation experiments were performed on the composite films contaminated by MB, and the result showed that Ag‐TiO₂‐APTES nanoparticle provided PVDF membrane with a certain photodegradation capacity under UV irradiation. Moreover, antibacterial activity of the composite membrane was also demonstrated through antibacterial experiment, Escherichia coli as the representative bacteria. Perhaps, this research may provide a new way for PVDF blending modification.     

Hexamethyldisiloxane‐modified ZnO‐SiO2‐coated superhydrophobic textiles for antibacterial application

A superhydrophobic cotton textile with high antibacterial properties has been fabricated. The cotton textile was coated through the in situ growth of ZnO‐SiO₂ nanoparticles in presence of chitosan as the template agent via a hydrothermal process at 95 °C. This process was followed by the coating of additional layers of hexadecyltrimethoxysilane (HDTMS). The obtained cotton textile showed antibacterial property against Staphylococcus epidermis and Escherichia coli with inhibition zones up to 18.26 and 8.48 mm, respectively. Scanning electron microscopy (SEM) revealed that the coating had a rough surface, which was attributed to the distribution of ZnO‐SiO₂ nanorods of hexagonal shape. This rough surface creates a superhydrophobic layer that repels the bacteria, as proven by the large water contact angle of approximately 150°. Nevertheless, the HDTMS layers prolong the durability of hydrophobicity for up to 3 h.     

Novel multifunctional water- and oil-repellent,antibacterial, and flame-retardant cellulose fibres created by the sol–gel process

This research aimed to prepare cotton fibres with novel multifunctional water- and oil-repellent, antibacterial, and flame-retardant properties. A three-component equimolar sol mixture, which included 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride, and P,P-diphenyl-N-(3-(trimethoxysilyl)propyl) phosphinic amide, was applied to the cotton fabric using the sol–gel process. The presence of the coating on the cotton fibres was confirmed by Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy. The functional properties of the coated cotton fabric were determined from liquid contact angle measurements and antibacterial activity, burning behaviour, and thermo-oxidative stability studies. The results demonstrate that a unique, compatible, and uniform organic-inorganic hybrid polymer network was formed on the fabric surface, which preserved its simultaneous hydrophobic (water contact angle of 135 ± 2°), oleophobic (n-hexadecane contact angle of 117 ± 1°), and bactericidal (bacterial reduction of 100 %) properties and incorporated the enhanced thermo-oxidative stability of the modified cellulose fibres.     

Synthesis and antibacterial activity of surface‐coated catechol‐conjugated polymer with silver nanoparticles on versatile substrate

In the present study, 2‐chloro‐3′,4′‐dihydroxyacetophenone (CCDP), a catechol derivative, was quaternized with poly(propylene oxide)‐g‐poly(dimethylaminoethyl methacrylate) (PPO‐g‐PDMA, PgP) to prepare surface coatings for various substrates. The surfaces of noble metals, oxides, and synthetic polymers were coated by immersion in an aqueous solution of CCDP quaternized with PgP (C‐PgP). The catechol functional groups that remained on the surface were used for deposition of Ag nanoparticles (AgNPs) on the coated surface, to provide a water‐resistant antibacterial polymer with long‐term antimicrobial activity. X‐ray photoelectron spectroscopy confirmed deposition of C‐PgP and AgNPs on the surface coated with the antibacterial polymer. Surface‐immobilized C‐PgP/AgNPs showed outstanding antibacterial activities against Staphylococcus aureus, a Gram‐positive bacterium, and Escherichia coli, a Gram‐negative bacterium. C‐PgP/AgNPs can be applied to a variety of substrates and can therefore be used as antibacterial materials in various fields. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface characteristic and cell response of CVD SiC coating for carbon/carbon composites used for hip arthroplasty

SiC coatings were applied on carbon/carbon composites by chemical vapor deposition for potential application in hip arthroplasty. The surface morphology, roughness, and wettability of the coatings were evaluated by scanning electron microscopy, laser confocal scanning microscope, and video‐based contact angle measuring device, respectively. The bonding strength between the coatings and carbon/carbon composites was analyzed by scratch testing. The cell responses to coatings were studied by analyzing the cell morphology and cell proliferation. The results showed that SiC coatings showed spherical morphology with a roughness of R_a = 1.0 ± 0.2 µm and a contact angle of 64.7 ± 4.0°. The coatings had lower surface roughness and better surface hydrophilicity compared with those of the uncoated carbon/carbon composites. A strong shear strength averaging 120.0 MPa between the coating and carbon/carbon composites was achieved. The cell culture experiments showed that cell spreading was improved, and cell proliferation was increased with the SiC coatings. It was demonstrated that CVD‐SiC‐coated carbon/carbon composites were good candidates as artificial hip joint materials. Copyright © 2012 John Wiley & Sons, Ltd.     

Surface characteristics and wetting properties of sol–gel coated base paper

Two hybrid coatings synthesized by using alkoxysilanes as precursors in a sol–gel process, differing from each other in terms of the organic components in alkoxysilanes, have been developed to improve the water repellent properties of base paper. The sol–gel‐coated base paper samples were characterized by scanning electron microscopy, atomic force microscopy, confocal laser scanning microscopy, X‐ray photoelectron spectroscopy, time‐of‐flight secondary ion mass spectrometry, and contact angle measurements. The sol–gel coatings were found to clearly change the surface properties of base paper. Thin coating layers were formed on base paper surfaces. The topographical data indicated the formation of discontinuous thin films; the time‐of‐flight secondary ion mass spectrometry analyses confirmed that the coatings were covering the fibres but only partially covered the fibre–fibre intersections. Water and the subsequent heat treatment used as a reference treatment reduced the surface roughness and porosity and slightly changed the surface chemistry of the base paper. The wettability and absorptivity of base paper was clearly reduced by the applied coatings. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and characterization of phenyl polysiloxane modified polyurea/polyurethanes

A series of phenyl polysiloxane‐modified polyurea/polyurethanes ( SPUs ) with different silicone loadings (10, 20, 30, and 40 wt %) have been designed and synthesized. The structures of SPUs were confirmed by ¹H NMR, ¹³C NMR, and FT‐IR. The impact of phenyl polysiloxane content on the properties of SPUs was fully studied. The residual methoxy groups on silicon could help SPUs form interpenetrating networks accompanying with the residual isocyanate under moisture, which was different with the conventional moisture‐crosslinking polyurethane system. The properties of SPUs films have been fully researched by attenuated total reflection flourier transformed infrared spectroscopy, thermal analysis, tensile tests, water contact angle, X‐ray photoelectron spectroscopy, SEM, and AFM. Results indicated that the introduction of phenyl polysiloxane improved the thermal stability and remarkably increased the water contact angles accompanying with a comparable mechanical strength to the pure polyurethane. Meanwhile, it also brought out the decreased microphase separation and water absorption. The obvious surface migration has been observed in the SPUs , which changed their surface properties. Some voids were observed in all moisture curing SPUs system, but the phenyl silicone content impacted on the numbers and sizes of the voids. The phenyl groups introduced and carbon dioxide produced in the crosslinking procedure helped to form and stabilize the voids in the SPUs . © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1794–1805     

Characterization and electric field dependence of N,N′‐bis(9H‐fluoren‐9‐ylidene)benzene‐1, 4‐diamine thin film/substrate interface

N,N′‐bis(9H‐fluoren‐9‐ylidene)benzene‐1,4‐diamine deposited onto highly oriented pyrolytic graphite (HOPG) was investigated by contact angle measurement(CAM), Raman spectroscopy and tunneling spectroscopy. The results of CAM and Raman spectra have confirmed that organic layers had deposited on substrate. Tunneling spectra obtained in the scanning tunneling microscopy measurement system were reported as a function of electrode potential. The tunneling current data were acquired at different electrode–electrode separations and depicted significant trend under the action of electric field. Under weak electric fields, the electrode–electrode separation has little effect on the potential of conductance peak. However, with the shrinkage of electrode–electrode separation, the electron transport model obeys the Ohmic law. Copyright © 2010 John Wiley & Sons, Ltd.     

The mycological effect on morphological,electrochemical and redox properties of the polyaniline surface

Biofilm formation with eight different microscopic fungi on the polyaniline surface and its effect on the morphological, electrochemical and redox properties have been studied. The investigations on selected Chrysosporium merdarium and Rhizomucor pusillus fungi behavior were performed. Conspicuous difference in the oxidation level, redox activity and oxalate impurities at the polymer surface layer treated with Chrysosporium merdarium and Rhizomucor pusillus was confirmed. The electrochemical behavior of the modified electrode was characterized using the cyclic voltammetry technique. The chemical composition of treated surface was determined by X‐ray photoelectron spectroscopy. For the estimation of conductive polymer morphology and roughness, the method of optical and scanning probe microscopy was applied, which showed that the polyaniline surfaces treated with Chrysosporium merdarium are homogenous and smoother than the polyaniline surfaces treated with Rhizomucor pusillus. Water contact angle measurements confirmed the effect of microbial growth on the properties of the polyaniline surface. Copyright © 2013 John Wiley & Sons, Ltd.     

Well‐defined polycaprolactone precursors for low surface‐energy polyurethane films

For the purpose of developing model coating systems, it is important to use well‐defined coating precursors. In this work, polyester oligomers were synthesized by controlled ring‐opening polymerization of ε‐caprolactone and 4‐tert‐butyl‐ε‐caprolactone via an activated monomer mechanism. These well‐defined oligomers, including 3‐armed hydroxyl‐functionalized polyesters and perfluoroalkyl‐end‐capped linear polyesters, have been obtained with controlled functionality and low‐molecular weight polydispersity and without the formation of cyclic structures, as demonstrated by MALDI‐ToF MS analyses. The polymer architecture and functionality can be tuned by using different initiating alcohols. These oligomers have been used as precursors to prepare model low surface‐energy polyurethane coatings. Upon the addition of about 1 wt % of fluorine in the polyurethane films, the advancing contact angles for water and hexadecane have been increased to 105° and 78°, respectively; the surface enrichment of fluorinated species has been confirmed by X‐ray photoelectron spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 218–227, 2008     

Preparation and characterization of PHB/PBAT–based biodegradable antibacterial hydrophobic nanofibrous membranes

In this study, polyhydroxybutyrate/poly(butyleneadipate‐co‐terephthalate) (PHB/PBAT) nanofibrous membranes were produced by electrospinning the blends of biodegradable PHB and PBAT. The antibacterial hydrophobic nanofiber membranes were obtained by grafting 1‐allylhydantoin and perfluorooctyl acrylate onto the PHB/PBAT membranes. The prepared nanofibrous membranes were chlorinated with chlorine bleach and characterized by scanning electron microscopy, Fourier transform infrared, and thermogravimetric analysis. The chlorinated nanofibrous membranes exhibited efficient antimicrobial activity against Escherichia coli O157:H7 (ATCC 43895) and Staphylococcus aureus (ATCC 6538) with 6.08 and 5.78 log reduction, respectively. The contact angle of this antibacterial membrane was 123.1° ± 1.9°. The treated membranes showed good stability and durability towards UV‐A light exposure and storage. Therefore, our designed antibacterial hydrophobic nanofibrous membranes may have great potential for use in food packaging.     

Full polysaccharide chitosan‐CMC membrane and silver nanocomposite: synthesis,characterization, and antibacterial behaviors

Chitosan‐carboxymethyl cellulose (CMC) full polysaccharide membrane was prepared by cross‐linking of chitosan with CMC dialdehyde and subsequent reductive amination. CMC dialdehyde molecule was prepared by periodate oxidation of CMC and then applied as a cross‐linking agent to form a new membrane network. The properties of oxidized CMC were investigated by various methods such as Fourier transform infrared (FT‐IR) spectroscopy, ¹H NMR spectroscopy, and viscosity test. Then, novel chitosan‐CMC silver nanocomposite was prepared using chitosan‐CMC as a carrier. The structure of the chitosan‐CMC membrane and the silver nanocomposite were confirmed by FT‐IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). TEM images indicate that the chitosan‐CMC nanocomposite comprises silver nanoparticles with diameters in the range of about 5–20 nm. The antibacterial studies of the nanocomposite were also evaluated. The chitosan‐CMC silver nanocomposite demonstrates good antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Copyright © 2016 John Wiley & Sons, Ltd.     

Nonbiofouling surface based on amphiphilic alkanethiol self‐assembled monolayers

A series of novel amphiphilic alkanethiols used for preparation of nonbiofouling surfaces have been synthesized and characterized. Surface properties of the resultant self assembled layers have been studied by multiple characterization techniques, such as XPS, Grazing angle infrared spectroscopy (GA‐FTIR) and contact angle measurements. The antifouling performance of surfaces grafted with terminally fluorinated alkanethiols were assayed employing the fouling diatom Nitzschia and ubiquitous Staphylococcus aureus. The results indicated that amphiphilic alkanethiol‐grafted surfaces could effectively reduce the bacterial adhesion and settlement of the fouling diatom. Copyright © 2010 John Wiley & Sons, Ltd.     

Photo‐crosslinked fluorinated thin films from azido‐functionalized random copolymers

Random copolymers of styrene, p‐azidomethylstyrene and 1H,1H,2H,2H‐perfluorodecyl methacrylate were prepared in two steps involving nitroxide‐mediated radical copolymerization and azidation reaction and further characterized by ¹H and ¹⁹F NMR, size exclusion chromatography, differential scanning calorimetry, and thermal gravimetric analysis. Ultrathin films of these azidomethyl‐functionalized fluorinated random copolymers, with thicknesses ranging from 20 to 100 nm, were spin coated onto Si substrates and then crosslinked by ultraviolet irradiation resulting in smooth and insoluble crosslinked fluorinated polymer mats. The surface properties of the supported thin films were investigated by X‐ray photoelectron spectroscopy and water contact angle measurements. These tailored photo‐crosslinked coatings afford a versatile control and homogenization of the wetting properties of different organic and inorganic substrates. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3888–3895, 2010     

Antibiotic glass slide coated with silver nanoparticles and its antimicrobial capabilities

Silver nanoparticles were covalently coated on a glass surface by overnight exposure of the glass substrate to nanoparticle solutions, using 3‐aminopropyltriethoxysilane (APTES) as a coupling agent. Washing and air‐drying yield a uniformly coated glass substrate, which can be used as a material capable of killing harmful microorganisms in food industry. Nanoparticles are stable on the glass surface and are not washed away by water; they even remain on the glass surface under short‐term ultrasonic irradiation. The morphology of silver nanoparticles on the glass substrate was characterized by scanning electron microscope (SEM). The existence of Ag nanoparticles on the substrate was also confirmed by ultraviolet‐visible (UV–Vis) spectroscopy. Fourier transform infrared (FT‐IR) measurement shows that the connection is based on covalent bonds between silver nanoparticle surface/APTES molecules. Combining the effects of low cost and effectiveness in prohibiting the growth of Escherichia coli, such materials are expected to be used as antibacterial coatings, which may have large potential applications in food industry. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation and characterization of nanostructured thin films of Au and Ag nanoparticles synthesized by ascorbic acid on modified glass surface

Immobilization of Ag and Au nanoparticles (NPs) synthesized by ascorbic acid on chemically modified glass surface has been studied. 3‐[2‐(2‐Aminoethylamino)ethylamino]propyl‐trimethoxysilane (AMPTS), N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilan, and 3‐trimethoxysilyl‐1‐propanethiol (MSPT) were used as surface modifying agents. To improve immobilization efficiency, the ammonia solution has been used along with the silane reagents, which assisted to adsorb the metal NPs on glass surface. It was found that AMPTS and MSPT have considerable effect on deposition of Ag and AuNPs on glass substrate. The fabricated thin films were characterized by using UV‐Vis spectroscopy, atomic force microscopy, energy‐dispersive X‐ray spectroscopy and subjected to antimicrobial resistance test. The UV–Vis spectra show a distinctive plasmon resonance absorbance peak for thin films of Au and AgNPs prepared with MSPT and AMPTS, respectively. Atomic force microscopy images indicate that formation of Au and AgNPs with spherical morphology after immobilization on the glass substrate and also the dimensions of NPs on the surface appear larger than those observed in the parent colloidal solution. Energy‐dispersive X‐ray spectroscopy measurements confirmed the presence of silver and gold on the modified glass surface, and elemental composition was measured. The Au and AgNPs thin films show antibacterial activity against gram negative (Escherichia coli) and gram positive (Staphylococcus aureus) bacteria in comparison with a blank sample. Copyright © 2015 John Wiley & Sons, Ltd.