Infrared characterization of biocidal nylon

Evaluation of Novel Antibacterial N-Halamine Nanoparticles Prodrugs towards Susceptibility of Escherichia coli Induced by DksA Protein

Novel N-halamine nanoparticles potentially useful for killing pathogenic bacteria, i.e., SiO2@PS/N-halamine NPs, were successfully synthesized via the immobilization of N-halamines onto the polystyrene-coated silica nanoparticles (SiO2@PS NPs). The effect of reaction conditions, i.e., chlorination temperature, bleaching concentration, chlorination time, on the oxidative chlorine content in the products was systematically investigated. The antibacterial activity of the products was tested via the modified plate counting methd using Escherichia coli (E. coli) as a model bacterium. The possible mechanism of the antibacterial action of the products was also studied using scanning electron microscopy combined with a inhibition zone study. The antimicrobial capability of the products was well controlled by tuning the oxidative chlorine content in the products. More importantly, the role of DksA protein in the susceptibility of E. coli against the products was proven using a time-kill assay. This in-depth investigation of the sensitivity of E. coli towards N-halamine NPs provides a systematic understanding of the utility of N-halamines for deactivating bacteria or even disease control.

Design, synthesis and biocidal effect of novel amine N-halamine microspheres based on 2,2,6,6-tetramethyl-4-piperidinol as promising antibacterial agents

Novel superior antibiotics, i.e. amine N-halamine nanoparticles were synthesized via the radical copolymerization, and their bactericidal effects were studied.

Antimicrobial N-halamine polymers and coatings: a review of their synthesis, characterization, and applications

Antimicrobial N-halamine polymers and coatings have been studied extensively over the past decade thanks to their numerous qualities such as effectiveness toward a broad spectrum of microorganisms, long-term stability, regenerability, safety to humans and environment and low cost. In this review, recent developments are described by emphasizing the synthesis of polymers and/or coatings having N-halamine moieties. Actually, three main approaches of preparation are given in detail: polymerization, generation by electrochemical route with proteins as monomers and grafting with precursor monomers. Identification and characterization of the formation of the N-halamine bonds (>N-X with X = Cl or Br or I) by physical techniques such as Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and by chemical reactions are described. In order to check the antimicrobial activity of the N-halamine compounds, bacterial tests are also described. Finally, some examples of application of these N-halamines in the water treatment, paints, healthcare equipment, and textile industries are presented and discussed.

Rechargeable biofilm-controlling tubing materials for use in dental unit water lines

A simple and practical surface grafting approach was developed to introduce rechargeable N-halamine-based antimicrobial functionality onto the inner surfaces of continuous small-bore polyurethane (PU) dental unit waterline (DUWL) tubing. In this approach, tetrahydrofuran (THF) solution of a free-radical initiator, dicumyl peroxide (DCP), flowed through the PU tubing (inner diameter of 1/16 in., or 1.6 mm) to diffuse DCP into the tubing's inner walls, which was used as initiator in the subsequent grafting polymerization of methacrylamide (MAA) onto the tubing. Upon chlorine bleach treatment, the amide groups of the grafted MAA side chains were transformed into acyclic N-halamines. The reactions were confirmed with attenuated total reflectance infrared (ATR) spectra and iodometric titration. The mechanical properties of the tubing were not significantly affected by the grafting reactions. The biofilm-controlling function of the new N-halamine-based PU tubing was evaluated with Pseudomonas aeruginosa (P. aeruginosa), one of the most isolated water bacteria from DUWLs, in a continuous bacterial flow model. Bacteria culturing and SEM studies showed that the inner surfaces of the new N-halamine-based PU tubing completely prevented bacterial biofilm formation for at least three to four weeks. After that, bacteria began to colonize the tubing surface. However, the lost function was fully regenerated by exposing the tubing inner surfaces to diluted chlorine bleach. The recharging process could be repeated periodically to further extend the biofilm-controlling duration for long-term applications.

Acyclic N-Halamine Polymeric Biocidal Films

Low concentrations of acyclic amide monomers, methacrylamide (MAM) and acrylamide (AM), were copolymerized with vinyl acetate (VAc). No significant differences between the synthesized copolymers and poly(VAc) were seen by 1H-NMR, FTIR, and DSC analysis. Biocidal films, formed by coating the copolymers onto polyester transparency slides and polyester fabric swatches, were chlorinated by exposure to sodium hypochlorite solutions. Both S. aureus and E. coli O157: H7 were completely inactivated within 1 min on the transparency slides and polyester fabric swatches derived from poly(VAc-co-MAM). The chlorine on the films was stable under UVA irradiation and the surfaces were rechargeable upon chlorine loss.

AcyclicN-halamine-based biocidal tubing: Preparation, characterization, and rechargeable biofilm-controlling functions

In this study, the surfaces of polypropylene tubing were hydroxylated with potassium persulfate. The resultant tubing surfaces were grafted with methacrylamide (MAA) using ceric(IV) ammonium nitrate as an initiator. Upon chlorination treatment with diluted chlorine bleach, some of the amide groups in the grafted MAA side chains were transformed into stable acyclic N-halamines. The reactions were confirmed with attenuated total reflectance infrared, X-ray photoelectron spectra, and iodimetric titration. The resultant tubing was challenged with Pseudomonas aeruginosa (P. aeruginosa) in a continuous flowing model. Bacteria culturing and scanning electron microscope studies showed that the chlorinated MAA-grafted tubing could provide potent and rechargeable biofilm-controlling functions against the test microorganisms.

Comparação de Técnicas FTIR de Transmissão, Reflexão e Fotoacústica na Análise de Poliamida-6, Reciclada e Irradiada

Um estudo comparativo envolvendo técnicas de análise por espectroscopia no infravermelho com transformada de Fourier (FTIR) de transmissão, reflexão e fotoacústica é apresentado com análise de poliamida-6. O potencial e as limitações destes métodos são investigados para analisar as alterações espectrométricas que ocorrem no interior e na superfície da poliamida-6, reciclada, e irradiada na presença de oxigênio, com feixe de elétrons de 1,5 MeV, na dose de 500 kGy. As técnicas mostram-se sensíveis para detectar pequenas mudanças de estruturas que ocorrem na poliamida-6 reciclada e irradiada. Os espectros sugerem formação de grupos --OH, HOC=O-, e -C=O, e mudanças estruturais relacionadas com grupos NH e -CN-C=O. Basicamente, as mesmas alterações espectrométricas são observadas com o uso das técnicas, sendo mais evidenciadas no interior das amostras pela espectroscopia-FTIR de transmissão, e na sua superfície, pela microscopia-FTIR.