Zwitterionic sulfobetaine polymers with a catechol chain end (DOPA-PSB) were applied to a variety of hydrophobic polymer sheets and fibers. In addition, a silica surface was tested as a representative hydrophilic substrate. The polymer-coated surfaces showed significantly lower fouling levels than uncoated controls. Because of the anti-polyelectrolyte nature of sulfobetaine zwitterionic polymers, the effect of salt concentration on the coating solutions and the quality of the polymer coating against fouling are studied. The coating method involves only water-based solutions, which is compatible with most surfaces and is environmentally friendly. To demonstrate the versatility of the reported method, we evaluated the fouling levels of the polymer coating on commonly used polymeric surfaces such as polypropylene (PP), polydimethylsiloxane (PDMS), polystyrene (PS), nylon, polyvinyl chloride (PVC), and poly(methyl methacrylate) (PMMA).

It is highly desirable to develop a universal nonfouling coating via a simple one-step dip-coating method. Developing such a universal coating method for a hydrophilic polymer onto a variety of surfaces with hydrophobic and hydrophilic properties is very challenging. This work demonstrates a versatile and simple method to attach zwitterionic poly(carboxybetaine methacrylate) (PCB), one of the most hydrophilic polymers, onto both hydrophobic and hydrophilic surfaces to render them nonfouling. This is achieved by the coating of a catechol chain end carboxybetaine methacrylate polymer (DOPA-PCB) assisted by dopamine. The coating process was carried out in water. Water miscible solvents such as methanol and tetrahydrofuran (THF) are added to the coatings if surface wettability is an issue, as for certain hydrophobic surfaces. This versatile coating method was applied to several types of surfaces such as polypropylene (PP), polydimethyl siloxane (PDMS), Teflon, polystyrene (PS), polymethylmethacrylate (PMMA), polyvinyl chloride (PVC) and also on metal oxides such as silicon dioxide.

Fabrication of a chemiresistive biosensor for detection of biomolecules is demonstrated on a high surface area, flexible electro‐spun nylon fiber mat. For the first time, the –OH functionalized conducting copolymer of 3,4‐ethylenedioxythiophene (EDOT) and 3‐thiopheneethanol (3‐TE) is synthesized and conformally deposited on the electro‐spun mats by oxidative chemical vapor deposition (oCVD). The free –OH functional groups of the copolymer are available for immobilization of analyte specific biomolecules. Here, avidin and biotin molecules are employed as the analyte‐specific molecule and analyte respectively for their high specificity to each other. The sensitivities of avidin immobilized conducting copolymer on electro‐spun mats are tested against micro‐molar to nano‐molar concentrations of biotin in aqueous solutions. Application of electro‐spun fiber mat in this case enhances the sensor response 6 times when compared to a flat substrate and also significantly lowers the response time. In addition to the experimental studies, current work also includes modeling of the kinetics of the change of response for the biotin‐avidin interactions as a function of time. Most importantly, this fabrication technique promises an extremely sensitive and field deployable method for the detection of other biomolecules, for example, food pathogens.

The incidence of foodborne outbreaks involving fresh produce is of worldwide concern. Lytic bacteriophage cocktails and a levulinic acid produce wash were investigated for their effectiveness against the foodborne pathogens Escherichia coli O157:H7, Shigella spp., and Salmonella on broccoli, cantaloupe, and strawberries. Inoculated samples were treated with bacteriophage cocktails (BC) before storage at 10°C for 24 h, a levulinic acid produce wash (PW) after storage at 10°C for 24 h, or a combination of the washes (BCPW) before and after storage. All three treatments were compared against a 200-ppm free available chlorine wash. Wash solutions were prepared using potable water and water with an increased organic content of 2.5 g/liter total dissolved solids and total organic carbon. BCPW was the most effective treatment, producing the highest log reductions in the pathogens. Produce treated with BCPW in potable water with a PW exposure time of 5 min resulted in the highest reduction of each pathogen for all samples tested. The type of produce and wash solution had significant effects on the efficacy of the individual treatments. The chlorine wash in water with higher organic content was the least effective treatment tested. An additive effect of BCPW was seen in water with higher organic content, resulting in greater than 4.0-log reductions in pathogens. Our findings indicate that the combination of antimicrobial BC with a commercial produce wash is a very effective method for treating produce contaminated with E. coli O157:H7, Shigella spp., and Salmonella even in the presence of high loads of organic matter.

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The interaction of cecropin P1 (CP1) with Escherichiacoli was investigated to gain insight into the time-dependent antimicrobial action. Biophysical characterizations of CP1 with whole bacterial cells were performed using both fluorescent and colorimetric assays to investigate the role of membrane permeability and lipopolysaccharide (LPS) binding in lytic behavior. The kinetics of CP1 growth inhibition assays indicated a minimal inhibitory concentration (MIC) of 3 microM. Bactericidal kinetics at the MIC indicated rapid killing of E.coli (<30 min). Membrane permeability studies illustrated permeation as a time-dependent event. Maximum permeability at the MIC occurred within 30 min, which correlates to the bactericidal action. Further investigation showed that the immediate permeabilizing action of CP1 is concentration-dependent, which correlates to the concentration-dependent nature of the inhibition assays. At the MIC and above, the immediate permeability was significant enough that the cells could not recover and exhibit growth. Below the MIC, immediate permeability was evident, but the level was insufficient to inhibit growth. Dansyl polymyxin B displacement studies showed LPS binding is essentially the same at all concentrations investigated. However, it does appear that only the immediate interaction is important, because binding continued to increase over time beyond cell viability. Our studies correlated CP1 bactericidal kinetics to membrane permeability suggesting CP1 concentration-dependent killing is driven by the extent of the immediate permeabilizing action of the peptide.

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The antibacterial effect of caprylic acid (35 and 50 mM) on Escherichia coli O157:H7 and total anaerobic bacteria at 39 degrees C in rumen fluid (pH 5.6 and 6.8) from 12 beef cattle was investigated. The treatments containing caprylic acid at both pHs significantly reduced (P < 0.05) the population of E. coli O157:H7 compared with that in the control samples. At pH 5.6, both levels of caprylic acid killed E. coli O157:H7 rapidly, reducing the pathogen population to undetectable levels at 1 min of incubation (a more than 6.0-log CFU/ml reduction). In buffered rumen fluid at pH 6.8, 50 mM caprylic acid reduced the E. coli O157:H7 population to undetectable levels at 1 min of incubation, whereas 35 mM caprylic acid reduced the pathogen by approximately 3.0 and 5.0 log CFU/ml at 8 and 24 h of incubation, respectively. At both pHs, caprylic acid had a significantly lesser (P < 0.05) and minimal inhibitory effect on the population of total anaerobic bacteria in rumen compared with that on E. coli O157:H7. At 24 h of incubation, caprylic acid (35 and 50 mM) reduced the population of total anaerobic bacteria by approximately 2.0 log CFU/ml at pH 5.6, whereas at pH 6.8, caprylic acid (35 mM) did not have any significant (P > 0.05) inhibitory effect on total bacterial load. Results of this study revealed that caprylic acid was effective in inactivating E. coli O157:H7 in bovine rumen fluid, thereby justifying its potential as a preslaughter dietary supplement for reducing pathogen carriage in cattle.