Preston A. Fulmer

Surface Self-Concentrating Amphiphilic Quaternary Ammonium Biocides as Coating Additives

A variety of amphiphilic quaternary dimethylammonium compounds bearing n-alkyl and oxyethylene groups have been designed and synthesized as antimicrobial additives for use in self-decontaminating surfaces. The effectiveness of these additives stems from a unique ability to self-concentrate at the air-polymer interface without the incorporation of exotic perfluorinated or polymeric functionalities. X-ray photoelectron spectroscopy analysis reveals surface enrichment as high as 18-fold, providing a 7-log reduction of both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The migration to the surface is a consequence of the hydrophobicity of the additive within the hydrophilic polyurethane resin, over which an unprecedented level of control can be exerted by altering the lengths of the n-alkyl and oxyethylene groups. Thus, for the first time, specific surface and bulk coating concentrations can be achieved as desired using a single class of antimicrobial additives.

Synthesis and Development of a Multifunctional Self-Decontaminating Polyurethane Coating

A unique, durable, nonleaching antimicrobial urethane coating possessing energy-dampening properties is reported. Five novel diol-functionalized quaternary ammonium bromide salts were designed, synthesized, and cross-linked with a commercial polyisocyanate to afford novel multifunctional self-decontaminating coatings. Leaching of the antimicrobial into the environment is eliminated because of the biocidal tether. The effectiveness of these molecules to self-concentrate at the air-polymer interface without addition of other surface modifying additives proved extremely advantageous, and consequently resulted in microphase separation as confirmed by AFM. The coatings were designed to continuously decontaminate against a variety of pathogenic bacteria in addition to affording preliminary dampening properties. Minimum inhibitory concentration studies as well as surface antimicrobial evaluations were conducted using both Gram-positive and Gram-negative bacteria. Additionally, viscoelastic properties, hardness, tack, and surface energy measurements were used to correlate with coating performance.

Development of antimicrobial peptides (AMPs) for use in self-decontaminating coatings.

Antimicrobial peptides (AMPs) are a class of short polypeptides usually associated with the host organisms innate immune system. AMPs have been identified in a wide range of host organisms, including plants, amphibians, fish, and humans. These peptides usually consist of 30-100 amino acids and are most often cationic. In addition to a net positive charge, AMPs often are amphipathic, containing both hydrophobic and hydrophilic domains. This property allows for increased interaction with and insertion into negatively charged cell walls and membranes of microbes. Because of the prevalence of antibiotic resistance among common human pathogens, recent research into AMPs has revolved around the attempt to increase the availability of drugs to which microbes are susceptible. Because the mechanism of kill for AMPs is different from that of most conventional antibiotics, which tend to be very specific in their targets, AMPs are thought to be a very attractive future substitute for traditional antibiotics. The development of novel self-decontaminating surfaces containing two AMPs previously isolated from Chrysophrys major is reported. These AMPs, Chrysophsin-1 and -3, demonstrated 1-4 logs kill of both Gram-positive and Gram-negative bacteria when incorporated into control acrylic coating systems.

Evidence for Singlet-Oxygen Generation and Biocidal Activity in Photoresponsive Metallic Nitride Fullerene−Polymer Adhesive Films

The adhesive properties, as measured by bulk tack analysis, are found to decrease in blends of isomerically pure Sc3N@I(h)-C80 metallic nitride fullerene (MNF) and polystyrene-block-polyisoprene-block-polystyrene (SIS) copolymer pressure-sensitive adhesive under white light irradiation in air. The reduction of tack is attributed to the in situ generation of 1O2 and subsequent photooxidative cross-linking of the adhesive film. Comparisons are drawn to classical fullerenes C60 and C70 for this process. This work represents the first demonstration of 1O2 generating ability in the general class of MNFs (M3N@C80). Additional support is provided for the sensitizing ability of Sc3N@I(h)-C80 through the successful photooxygenation of 2-methyl-2-butene to its allylic hydroperoxides in benzene-d(6) under irradiation at 420 nm, a process that occurs at a rate comparable to that of C(60). Photooxygenation of 2-methyl-2-butene is found to be influenced by the fullerene sensitizer concentration and O2 flow rate. Molar extinction coefficients are reported for Sc3N@I(h)-C80 at 420 and 536 nm. Evaluation of the potential antimicrobial activity of films prepared in this study stemming from the in situ generation of 1O2 led to an observed 1 log kill for select Gram-positive and Gram-negative bacteria.

Development of broad-spectrum antimicrobial latex paint surfaces employing active amphiphilic compounds.

With the increase in antibiotic-resistant microbes, the production of self-decontaminating surfaces has become an area of research that has seen a surge of interest in recent years. Such surfaces, when incorporated into commercial products such as childrens toys, medical devices and hospital surfaces could reduce the number of infections caused by pathogenic microorganisms. A number of active components for self-decontaminating surfaces have been investigated, including common antibiotics, metal ions, quaternary ammonium salts (QAS), and antimicrobial peptides (AMP). A recent research focus has been development of a wide range of amphiphilic antimicrobial additives that when combined with modern low volatile organic compound (VOC), water-based paints leads to a surface concentration of the active compounds as the coating cures. Herein we report the development of antimicrobial coatings containing a variety of additives, both QAS and AMP that are active against a broad-spectrum of potentially pathogenic bacteria (1-7 log kill), as well as enveloped viruses (2-7 log kill) and fungi (1-2 log kill). Additionally, these additives were compatible with water-dispersed acrylate coatings (latex paint) which have a broad range of real world applicability, and remained active for multiple challenges and when exposed to various cleaning scenarios in which they might encounter in real world situations.

Enhancing the Fouling Resistance of Biocidal Urethane Coatings via Surface Chemistry Modulation

A group of novel cross-linked polyurethane materials with varying ratios of hydroxyl-terminated macrodiols and tethered quaternary ammonium biocides have been prepared. The resulting materials had a wide range of thermal, mechanical, and surface properties, dictated by the macrodiol composition and biocide concentration. The complex interplay between surface chemistry and biocide concentration was shown to have a profound effect on the fouling resistance of these materials. While the combination of quaternary ammonium salt (QAS) diols with poly(tetramethylene oxide) macrodiols did not result in any enhancement of fouling resistance, addition of biocides to poly(ethylene glycol)-containing urethanes resulted in up to a 90% increase in biocidal activity compared to control materials while reducing the ability for microbes to adhere to the surface by an additional 60%. Materials prepared with polybutadiene macrodiols underwent a thermally induced oxidation, resulting in partial decomposition of the quaternary ammonium salt biocide and joint antimicrobial activity arising from remaining QAS and peroxide compounds.

Biodegradation of medium chain hydrocarbons by Acinetobacter venetianus 2AW immobilized to hair-based adsorbent mats†

The natural attenuation of hydrocarbons can be hindered by their rapid dispersion in the environment and limited contact with bacteria capable of oxidizing hydrocarbons. A functionalized composite material is described herein, that combines in situ immobilized alkane‐degrading bacteria with an adsorbent material that collects hydrocarbon substrates, and facilitates biodegradation by the immobilized bacterial population. Acinetobacter venetianus 2AW was isolated for its ability to utilize hydrophobic n‐alkanes (C10–C18) as the sole carbon and energy source. Growth of strain 2AW also resulted in the production of a biosurfactant that aided in the dispersion of complex mixtures of hydrophobic compounds. Effective immobilization of strain 2AW to the surface of Ottimat™ adsorbent hair mats via vapor phase deposition of silica provided a stable and reproducible biocatalyst population that facilitates in situ biodegradation of n‐alkanes. Silica‐immobilized strain 2AW demonstrated ca. 85% removal of 1% (v/v) tetradecane and hexadecane within 24 h, under continuous flow conditions. The methodology for immobilizing whole bacterial cells at the surface of an adsorbent, for in situ degradation of hydrocarbons, has practical application in the bioremediation of oil in water emulsions. Published 2011 American Institute of Chemical Engineers Biotechnol Prog., 2011

Printing soil: a single‐step, high‐throughput method to isolate micro‐organisms and near‐neighbour microbial consortia from a complex environmental sample

Summary Traditional high throughput methods for isolating microorganisms from environmental samples such as soil or sediment require pre-processing steps to remove the living species from their solid-phase microniche, creating a liquid-phase sample. This process destroys near-neighbor relationships that could be crucial to culturing and studying the microorganisms to be isolated. An automated, high throughput method is described here that isolates pure microbial cultures and spatially related microbial consortia directly from a solid-phase complex environmental sample. By using an orifice-free printing mechanism, Biological Laser Printing (BioLP) enabled single-step isolation of viable environmental microorganisms directly from soil. Soil was spread onto a titania-coated quartz plate prior to initiating printing of soil micro-particles with focused ultraviolet laser pulses. Tunable amounts of soil were printed to glass slides, Luria Bertani agar plates and broth filled 96-well plates at deposition rates exceeding 20 micro-particles per second, demonstrating the ability to isolate thousands of micro-particles of soil in minutes. Viability, culturability and significant morphological diversity were demonstrated post-printing. Results show that single step soil printing can be used to (a) generate pure microbial cultures (isolates), and (b) isolate consortia from a micro-ecological system that exists naturally in near-neighbor proximity, undisturbed from the environmental sample.

Thermal polycondensation of poly(diol citrate)s with tethered quaternary ammonium biocides

The synthesis and characterization of a series of novel, antimicrobial, aliphatic polyesters based on citric acid, alkanediols, and quaternary ammonium salt (QAS) diols is described. These materials possess a wide range of mechanical and thermal properties (storage modulus, E′ = 1.03–17.53 MPa at 25 °C; Tg = −15.7–38.6 °C) primarily dictated by alkanediol selection and the presence of biocide. Surface analysis via contact angle and FTIR-ATR studies indicate the presence of biocide at the material/air interface providing high antimicrobial activity (5–7 log kill of S. aureus over controls) for all materials containing tethered QAS. Hydrolysis of these cross-linked materials was also highly controlled based on the QAS, alkanediol structure, and curing duration; and significant hydrolysis occurs in as little as 4 weeks.

Coatings Capable of Germinating and Neutralizing Bacillus anthracis Endospores

Endospores are formed by various bacterial families, including Bacillus and Clostridium, in response to environmental stresses as a means to survive conditions inhospitable to vegetative growth. Although metabolically inert, the endospore must interact with its environment to determine an optimal time to return to a vegetative state, a process known as germination. Germination has been shown to occur in response to a variety of chemical stimuli from specific nutrient germinants including amino acids, sugars and nucleosides. This process is known to be mediated primarily by the GerA family of spore-specific receptor proteins which initiates a signal transduction cascade that results in a return of oxidative metabolism in response to germinant receptor interactions. Herein, we report the development of a novel coating system capable of germinating B. anthracis endospores, followed by rapid killing of the vegetative bacteria by a novel incorporated amphiphilic biocide. The most effective formulation tested exhibited an ability to germinate and kill B. anthracis endospores and vegetative bacteria, respectively. The formulation reported resulted in a 90% reduction in as little as 5 min, and a 6 log reduction by 45 min.