We present a simple method of fabricating highly potent dual action antibacterial composites consisting of a cationic polymer matrix and embedded silver bromide nanoparticles. A simple and novel technique of on-site precipitation of AgBr was used to synthesize the polymer/nanoparticle composites. The synthesized composites have potent antibacterial activity toward both gram-positive and gram-negative bacteria. The materials form good coatings on surfaces and kill both airborne and waterborne bacteria. Surfaces coated with these composites resist biofilm formation. These composites are different from other silver-containing antibacterial materials both in the ease of synthesis and in the use of a silver salt nanoparticle instead of elemental silver or complex silver compounds. We also demonstrate the ability to tune the release of biocidal Ag(+) ions from these composites by controlling the size of the embedded AgBr nanoparticles. These composites are potentially useful as antimicrobial coatings in a wide variety of biomedical and general use applications.

Synthetic amphiphilic polymers that mimic the membranedisrupting properties of natural antimicrobial peptides [1] show potent biocidal activity towards bacteria, [2][3][4] fungi, [5] and viruses.[6] Their easy synthesis, stability towards enzymatic degradation, and facile chemical tailoring make them promising candidates as novel chemical disinfectants and nonleaching biocides for a variety of biomedical applications. However, there is a delicate balance between useful biocidal activity and detrimental toxicity towards mammalian cells. Herein, we report the interplay between the chemical structure and antibacterial versus hemolytic properties of amphiphilic pyridinium polymers.The membrane-disrupting activity of amphiphilic polymers is mainly dependent on the charge and hydrophobicity, which have to be optimized to cause membrane disruption. [4,7,8] Structure-activity relationships have previously been reported on the effect of the length of the alkyl tail, an increase in the positive charge, and the overall hydrophobicity/hydrophilicity of the polymer on the membrane-disrupting activity. [7][8][9][10][11][12][13][14] All these variables also influence the balance between the antimicrobial and the hemolytic (toxicity) properties of the amphiphilic polymers. An important, yet unexplored, question is how the activity of an amphiphilic polycation varies as a function of the spatial positioning of the positive charge and the hydrophobic alkyl tail. For example, would the antibacterial and hemolytic activity of a polycation be any different if the positive charge and the alkyl tail were on the same center, as opposed to being spatially separated? We address this and related questions by comparing series of homologous amphiphilic pyridinium polymers that differ only in how the positive charge and the alkyl tail are spatially related. We observe that the spatial positioning of the charge and tail significantly influences the toxicity of these polymers, and this result may be used as a guiding principle in the design of polymeric antimicrobial compounds with reduced toxicity.Two series (A and B) of amphiphilic pyridinium-methacrylate copolymers differing only in the spatial positioning of the positive charge and the alkyl tail were synthesized as shown in Scheme 1. Series A consisted of pyridiniummethacrylate copolymers in which the positive charge and the alkyl tail are on the same center. A copolymer consisting of approximately 50 mol % vinylpyridine (VP) units and about 50 mol % methyl methacrylate (MMA) units was synthesized by radical polymerization. All the pyridine units were then completely N alkylated by heating with an excess of the respective n-iodoalkane. This process yielded six cationic polymers in series A, that is, A 2 , A 3 , A 4 , A 6 , A 8 , and A 10 with alkyl tails that were 2, 3, 4, 6, 8, and 10 carbon atoms long, respectively. Series B consisted of vinylpyridinium-alkyl methacrylate copolymers in which the positive charge and the alkyl tail are on separate centers. Copolymers of VP with different n...

Inspired by the superhydrophobic effect displayed in nature, we set out to mimic the interplay between the chemistry and physics in the lotus leaf to see if the same design principle can be applied to control wetting and adhesion between toners and inks on various printing surfaces. Since toners and inks are organic materials, superoleophobicity has become our design target. In this work, we report the design and fabrication of a model superoleophobic surface on silicon wafer. The model surface was created by photolithography, consisting of texture made of arrays of ∼3 μm diameter pillars, ∼7 μm in height with a center-to-center spacing of 6 μm. The surface was then made oleophobic with a fluorosilane coating, FOTS, synthesized by the molecular vapor deposition technique with tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane. Contact angle measurement shows that the surface exhibits super repellency toward water and oil (hexadecane) with a water and hexadecane contact angles at 156° and 158°, respectively. Since the sliding angles for both liquids are also very small (∼10°), we conclude that the model surface is both superhydrophobic and superoleophobic. By comparing with the contact angle data of the bare silicon surfaces (both smooth and textured), we also conclude that the superoleophobicity is a result of both surface texturing and fluorination. Results from investigations of the effects of surface modification and pillar geometry indicate that both surface oleophobicity and pillar geometry are contributors to the superoleophobicity. More specifically, we found that superoleophobicity can only be attained on our model textured surface when the flat surface coating has a relatively high oleophobicity (i.e., with a hexadecane contact angle of >73°). SEM examination of the pillars with higher magnification reveals that the side wall in each pillar is not smooth; rather it consists of a ∼300 nm wavy structure (due to the Bosch etching process) from top to bottom. Comparable textured surfaces with (a) smooth straight side wall pillars and (b) straight side wall pillars with a 500 nm re-entrant structure made of SiO(2) were fabricated and the surfaces were made oleophobic with FOTS analogously. Contact angle data indicate that only the textured surfaces with the re-entrant pillar structure are both superoleophobic and superhydrophobic. The result suggests that the wavy structure at the top of each pillar is the main geometrical contributor to the superoleophobic property observed in the model surface.

Synthetic amphiphilic polymers that mimic the membranedisrupting properties of natural antimicrobial peptides [1] show potent biocidal activity towards bacteria, [2][3][4] fungi, [5] and viruses. [6] Their easy synthesis, stability towards enzymatic degradation, and facile chemical tailoring make them promising candidates as novel chemical disinfectants and nonleaching biocides for a variety of biomedical applications. However, there is a delicate balance between useful biocidal activity and detrimental toxicity towards mammalian cells. Herein, we report the interplay between the chemical structure and antibacterial versus hemolytic properties of amphiphilic pyridinium polymers.The membrane-disrupting activity of amphiphilic polymers is mainly dependent on the charge and hydrophobicity, which have to be optimized to cause membrane disruption. [4,7,8] Structure-activity relationships have previously been reported on the effect of the length of the alkyl tail, an increase in the positive charge, and the overall hydrophobicity/hydrophilicity of the polymer on the membrane-disrupting activity. [7][8][9][10][11][12][13][14] All these variables also influence the balance between the antimicrobial and the hemolytic (toxicity) properties of the amphiphilic polymers. An important, yet unexplored, question is how the activity of an amphiphilic polycation varies as a function of the spatial positioning of the positive charge and the hydrophobic alkyl tail. For example, would the antibacterial and hemolytic activity of a polycation be any different if the positive charge and the alkyl tail were on the same center, as opposed to being spatially separated? We address this and related questions by comparing series of homologous amphiphilic pyridinium polymers that differ only in how the positive charge and the alkyl tail are spatially related. We observe that the spatial positioning of the charge and tail significantly influences the toxicity of these polymers, and this result may be used as a guiding principle in the design of polymeric antimicrobial compounds with reduced toxicity.Two series (A and B) of amphiphilic pyridinium-methacrylate copolymers differing only in the spatial positioning of the positive charge and the alkyl tail were synthesized as shown in Scheme 1. Series A consisted of pyridiniummethacrylate copolymers in which the positive charge and the alkyl tail are on the same center. A copolymer consisting of approximately 50 mol % vinylpyridine (VP) units and about 50 mol % methyl methacrylate (MMA) units was synthesized by radical polymerization. All the pyridine units were then completely N alkylated by heating with an excess of the respective n-iodoalkane. This process yielded six cationic polymers in series A, that is, A 2 , A 3 , A 4 , A 6 , A 8 , and A 10 with alkyl tails that were 2, 3, 4, 6, 8, and 10 carbon atoms long, respectively. Series B consisted of vinylpyridinium-alkyl methacrylate copolymers in which the positive charge and the alkyl tail are on separate centers. Copolymers of VP with different ...

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We demonstrate a versatile methodology combining both covalent surface anchoring and polymer cross-linking that is capable of forming long-lasting coatings on reactive and nonreactive surfaces. Polymers containing reactive methoxysilane groups form strong Si-O-Si links to oxide surfaces, thereby anchoring the polymer chains at multiple points. The interchain cross-linking of the methoxysilane groups provides additional durability to the coating and makes the coatings highly resistant to solvents. By tailoring the chemical structure of the polymer, we were able to control the surface energy (wetting) of a variety of surfaces over a wide range of water contact angles of 30-140 degrees . In addition, we synthesized covalently linked layer-by-layer polymeric assemblies from these novel methoxysilane polymers. Finally, antibacterial agents, such as silver bromide nanoparticles and triiodide ions, were introduced into these functional polymers to generate long-lasting and renewable antiseptic coatings on glass, metals, and textiles.

Composite materials made up from a pyridinium polymer matrix and silver bromide nanoparticles embedded therein feature excellent antimicrobial properties. Most probably, the antimicrobial activity is related to the membrane-disrupting effect of both the polymer matrix and Ag(+) ions; both may work synergistically. One of the most important applications of antimicrobial materials would be their use as surface coatings for percutaneous (skin-penetrating) catheters, such as central venous catheters (CVCs). These are commonly used in critical care, and serious complications due to bacterial infection occur frequently. This study aimed at examining the possible effects of a highly antimicrobial pyridinium polymer/AgBr composite on the blood coagulation system, i.e., (i) on the coagulation cascade, leading to the formation of thrombin and a fibrin cross-linked network, and (ii) on blood platelets. Evidently, pyridinium/AgBr composites could not qualify as coatings for CVCs if they trigger blood coagulation. Using a highly antimicrobial composite of poly(4-vinylpyridine)-co-poly(4-vinyl-N-hexylpyridinium bromide) (NPVP) and AgBr nanoparticles as a thin adherent surface coating on Tygon elastomer tubes, it was found that contacting blood platelets rapidly acquire a highly activated state, after which they become substantially disrupted. This implies that NPVP/AgBr is by no means blood-compatible. This disqualifies the material for use as a CVC coating. This information, combined with earlier findings on the hemolytic effects (i.e., disruption of contacting red blood cells) of similar materials, implies that this class of antimicrobial materials affects not only bacteria but also mammalian cells. This would render them more useful outside the biomedical field.

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