The use of conducting polymers as coating layers for the protection of surfaces against corrosion represents an important topic for investigation, as reported in the literature. In this work, polypyrrole/Fe3O4 nanoparticles (Fe3O4_NPs/PPy) hybrid nanocomposites (HN) were incorporated as anticorrosive additives in an epoxy paint to protect SAE 1010 carbon steel from corrosion. The HN particles were obtained by chemical polymerization of pyrrole in an aqueous solution in the presence of Fe3O4_NPs and were characterized by infrared absorption spectrophotometry, dynamic light scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy (TEM). The electrochemical impedance spectroscopy (EIS) was used in the analysis of the electrochemical response of the coated surface with and without HN. DLS data showed that the Fe3O4_NPs and Fe3O4_NPs/PPy obtained in solution present average diameters of (19.7 ± 9.6) nm and (63.5 ± 27.7) nm, respectively. TEM images showed Fe3O4_NPs with smaller sizes (10 nm - 30 nm), and that the HN had diameters smaller than 100 nm, consisting of Fe3O4 cores coated with polypyrrole. EIS measurements have shown that the addition of HN to the epoxy paint could improve the efficiency of the anticorrosive coating when compared to the original epoxy paint prepared without any corrosion inhibitor.

The production of conductive and organic devices from a 3D printer represents a promising strategy for several areas. In particular, the synthesis of polypyrrole-coated acrylonitrile butadiene styrene (ABS) composites can be considered an important step to produce conductive supports for 3D printing. Herein, it is reported the production of ABS samples through the additive manufacturing process (3D printing) accordingly to the Fused Deposition Modeling (FDM) method. The hydrophilic behavior was controlled by the surface treatment using air plasma for the following step of coating with polypyrrole (PPy) via an in situ polymerization, using two different oxidants: ferric chloride (FeCl3.6H2O) and ammonium persulfate (APS). The chemical, optical, surface, and electrical properties of these materials were characterized through Fourier Transform infrared spectroscopy (FTIR), contact angle measurements, cyclic voltammetry, Scanning Electron Microscopy (SEM), 4-probe electrical measurement, and mechanical tensile testing. The ABS/PPy (FeCl3) composite exhibited a low electrical contact resistance and better performance for applications that require electrodes with a good conductance level.

RESUMO: Bactérias do gênero Aeromonas são patógenos altamente disseminados no ambiente aquático, responsáveis por grandes perdas econômicas na piscicultura de diversos países. São micro-organismos oportunistas e sua patogenicidade está ligada a alguns fatores de virulência, como a formação de biofilme. O estresse salino é um dos fatores que favorecem a formação dessas colônias e, consequentemente, o aumento de infecções. Essas infecções quando estão associadas ao biofilme são ainda mais resistentes aos antimicrobianos. Nesse contexto, o polipirrol destaca-se como uma alternativa antimicrobiana por possuir vários atributos terapêuticos e não apresentar toxicidade aos organismos. Dessa forma, o objetivo desse estudo foi avaliar o perfil de susceptibilidade e a capacidade de formação de biofilme dos isolados de Aeromonas spp. associados aos diferentes níveis de salinidade e polipirrol. Determinou-se a atividade antibacteriana dos isolados e ensaios de motilidade foram realizados com bactérias que carreavam o gene fla. Também verificou-se a capacidade do cloreto de sódio e polipirrol em interferir na formação do biofilme. Os resultados foram evidenciados com a microscopia eletrônica de varredura. As concentrações de 2 e 3% de NaCl inibiram a motilidade bacteriana. Na formação do biofilme, 83% dos isolados bacterianos induziram a produção na concentração de 0,25%. O polipirrol causou a morte de todos os isolados testados na concentração de 125μg/mL. Além disso, esse composto diminuiu a motilidade bacteriana nas concentrações de 0,25 a 3%, sendo que em relação à produção de biofilme, não houve interferência. Esses resultados evidenciam que os diferentes níveis de NaCl influenciam na formação do biofilme favorecendo a persistência da infecção. Este estudo também realçou a potencialidade do polipirrol como agente bactericida, sendo uma alternativa eficaz às drogas antimicrobianas para o tratamento das infecções causadas por Aeromonas spp.

ABSTRACT: Bacteria of the genus Aeromonas are highly disseminated pathogens in the aquatic environment, responsible for great economic losses in the pisciculture of several countries. They are opportunistic microorganisms and their pathogenicity is linked to some virulence factors, such as biofilm formation. Saline stress is one of the factors that favor the formation of these colonies and, consequently, the increase of infections. These infections, when associated with biofilm, are even more resistant to antimicrobials. In this context, polypyrrole stands out as an antimicrobial alternative because it has several therapeutic attributes and does not present toxicity to organisms. Thus, the objective of this study was to evaluate the susceptibility profile and the biofilm formation capacity of Aeromonas spp. associated with different levels of salinity and polypyrrole. The antibacterial activity of the isolates was determined and motility assays were performed with bacteria bearing the fla gene. The ability of sodium chloride and polypyrrole to interfere with biofilm formation has also been demonstrated. The results were evidenced with scanning electron microscopy. Concentrations of 2 and 3% of NaCl inhibited bacterial motility. In the biofilm formation, 83% of the bacterial isolates induced production at the concentration of 0.25%. Polypyrrole caused the death of all the isolates tested at the concentration of 125μg/mL. In addition, this compound decreased bacterial motility at concentrations of 0.25 to 3%, and no biofilm was produced. These results show that the different levels of NaCl influence in the formation of the biofilm favoring the persistence of the infection. This study also highlighted the potential of polypyrrole as a bactericidal agent, being an effective alternative to antimicrobial drugs for the treatment of infections caused by Aeromonas spp.

RESUMO: O uso indiscriminado de antimicrobianos tem proporcionado a algumas bactérias patogênicas a seleção de cepas multirresistentes, situação que pode ser agravada pela formação do biofilme. Desta forma, as nanopartículas de prata (AgNPs) vêm se destacando como uma alternativa inovadora, de baixo custo e eficiente contra doenças causadas por bactérias. O objetivo deste estudo foi determinar a atividade antimicrobiana das AgNPs e a interferência na formação do biofilme de Aeromonas spp. obtidas de organismos aquáticos. As AgNPs foram sintetizadas quimicamente utilizando como agente redutor o citrato trissódico e caracterizadas por espectrofotometria ultravioleta-visível (UV-Vis). A atividade antimicrobiana foi realizada contra três isolados pelo método de microdiluição em caldo para determinar a concentração bactericida mínima (CBM) e um cultivo com CCCP, um inibidor da bomba de efluxo, foi realizado para complementar o efeito das AgNPs. A interferência no biofilme foi realizada segundo o protocolo de formação e consolidado, além da caracterização desta estrutura de resistência por microscopia eletrônica de varredura. No teste da CBM, as AgNPs não foram capazes de inativar o crescimento dos isolados, ao passo que o nitrato de prata obteve eficiência em diferentes concentrações. Na presença do inibidor de bomba de efluxo, dos isolados analisados, um passou de resistente a sensível na presença das nanopartículas. As AgNPs foram eficazes em diminuir a formação de biofilme, como também atuaram sobre o biofilme consolidado em todos os isolados testados. Estes resultados indicam o potencial das nanopartículas de prata em interferir com o biofilme de Aeromonas spp. de organismos aquáticos e seres humanos.

ABSTRACT: The indiscriminate use of antibiotics has selected some pathogenic bacteria being multidrug-resistant, a situation that can be exacerbated by biofilms formation. Thus, silver nanoparticles (AgNPs) have been highlighted as an innovative alternative, low-cost and effective against bacterial diseases. The aim of this study was to determine the antimicrobial activity of AgNPs and the interference in Aeromonas spp. biofilm formation. The strains were obtained from aquatic organisms. The AgNPs were chemically synthesized using as reducing agent trisodium citrate and characterized by ultraviolet-visible spectroscopy (UV-Vis). The antimicrobial activity was carried out against three isolates by the microdilution broth method for determining minimum bactericidal concentration (CBM) and cultivation of CCCP, an inhibitor of the efflux pump, was carried out to complement the effect of AgNPs. Interference in the biofilm formation was performed according to the protocol and consolidated, within the resistance structure characterization by scanning electron microscopy. In the test of the CBM, the AgNPs were unable to inactivate the growth of the isolates, while the silver nitrate obtained efficiency in different concentrations. In the efflux pump inhibitor presence the isolates were analyzed, one went from resistant to nanoparticles to sensitive. The AgNPs were effective in reducing of biofilm formation and acted on the consolidated biofilm in all tested isolates. These results indicate the silver nanoparticles to interfere with Aeromonas spp. biofilm from aquatic organisms and human bodies.

Dielectric characterization has been applied as a convenient tool for evaluation of transport and polarization mechanisms in soft materials. In this work, we have explored the study of charge transport mechanisms in alginate hydrogel containing neomycin-loaded liposomes. For comparison, drug release kinetic was evaluated by using UV-Vis spectrophotometry and electrical impedance spectroscopy (EIS) at different external direct current (DC) polarization (100 mV and 1 V). The charge transfer resistance (Rct) was proportional to DC electrical stimulation and inversely to the amount of released neomycin. Optical and electrical measurements confirmed the dependence of neomycin release under influence of electrical potentials. The kinetic profile of these systems was described by zero-order model. In addition, the Korsmeyer-Peppas model also suggested a diffusion mechanism based on super case II transport (non-Fickian). These results encouraged the use of EIS as a “dark" spectroscopy technique, since EIS is effective for studies of release kinetics controlled by DC external electrical excitation.

The development of organic devices based on conducting polymers for biofilm detection requires the combination of superior electrical response and high surface area for biofilm incorporation. Polypyrrole is a potential candidate for application in biofilm detection and control due to its characteristic superior electrical response and strong interaction with bacteria, which enables the use of the bioelectric effect in resulting devices. In this study, chemically synthesized polypyrrole was applied as a support for biofilm growth of S. aureus. Modifications in the electrical response of the polymeric template were explored to identify general mechanisms established during the deposition of the biofilm.

Large scale preparation of hybrid electrical actuators represents an important step for the production of low cost devices. Interfacial polymerization of polypyrrole in the presence of multi-walled carbon nanotubes represents a simple technique in which strong interaction between components is established, providing composite materials with potential applications as actuators due to the synergistic interaction between the individual components, i.e., fast response of carbon nanotubes, high strain of polypyrrole, and diversity in the available geometry of resulting samples.

Compósitos de poli(álcool vinílico)/dióxido de titânio preparados pela técnica de eletrofiação são potenciais candidatos para aplicações nas quais grande absorbância na região do ultra-violeta e transparência na região do visível são requeridas. A incorporação de semicondutor nas fibras pode ser inferida pela redução da impedância elétrica das fibras fabricadas por eletrofiação, como consequência do aumento na densidade de grãos de semicondutor dispersos nas fibras poliméricas. As propriedades térmicas do compósito polímero/semicondutor são dominadas pela resposta do PVA sendo a influência do dióxido de titânio detectada no espectro de absorção de luz pela maximização da absorbância na faixa de 240 nm a 400 nm. Os resultados indicam que o compósito de PVA/TiO2 pode ser convenientemente aplicado como curativo com proteção adicional contra efeitos de radiação ultravioleta (UVA e UVB) na pele humana. Uma aplicação adicional para o compósito PVA/TiO2 foi abordada com o estudo dos processos fotocatalíticos na degradação da rodamina B.

Electrospun composites of polyvinyl alcohol/titanium dioxide are potential candidates for applications that require high level of absorbance in the UV and transparency in the visible region. The incorporation of semiconductor particles in the core of fibers can be inferred from the reduction in the electrical impedance of electrospun fibers, as a consequence of the increased density of semiconductor granules along the fiber. The thermal properties of PVA dominate in the complete response of the composite while the influence from titanium dioxide is noted with an increased absorption from 240 nm to 400 nm. The results indicate that the PVA/TiO2 composites can be applied as wound dressing with additional protection against effects of ultraviolet radiation (UVA and UVB) on human skin. An additional application studied here was based on the use of PVA/TiO2 nanocomposites as active agent in photodegrading rhodamine B.

Neste trabalho, compósitos híbridos metal/polímero (nanopartículas de ouro/polipirrol) foram sintetizados a partir da polimerização química do pirrol sobre a superfície de nanopartículas metálicas estabilizados por um agente surfactante (dodecil sulfato de sódio). A posterior solubilização do compósito em álcool polivinílico permitiu a obtenção de uma matriz orgânica auto-sustentável, flexível, com boa resistência mecânica e aplicável na detecção de compostos voláteis (com especial atenção ao metanol). Nessa direção, foram otimizadas as condições de preparação do compósito, no sentido de promover a detecção e quantificação do metanol em misturas com etanol, com o intuito de aplicar o dispositivo no reconhecimento de resquícios de metanol em bebidas alcoólicas. Dos sistemas analisados, a sensibilidade dos dispositivos se mostrou diretamente proporcional à constante dielétrica do volátil utilizado, indicando que interações físicas ocorrem na matriz na presença de voláteis.

In this study, hybrid composites of gold nanoparticles and polypyrrole (AuNPs-PPy) were manufactured by chemical polymerization of the pyrrole monomer on the surface of metal nanoparticles, which were then incorporated in a poly(vinyl alcohol) (PVA) matrix to be exploited in sensing technologies for detecting methanol. The preparation conditions were optimized to maximize sensitivity, allowing for the determination of relative concentrations of methanol molecules in binary mixtures of methanol/ethanol. This was carried out using the electrical response of the sensor, which depends on the dielectric constant of the volatile organic compounds.