Microfluidic approaches to bacterial biofilm formation

Bacterial biofilms-aggregations of bacterial cells and extracellular polymeric substrates (EPS)-are an important subject of research in the fields of biology and medical science. Under aquatic conditions, bacterial cells form biofilms as a mechanism for improving survival and dispersion. In this review, we discuss bacterial biofilm development as a structurally and dynamically complex biological system and propose microfluidic approaches for the study of bacterial biofilms. Biofilms develop through a series of steps as bacteria interact with their environment. Gene expression and environmental conditions, including surface properties, hydrodynamic conditions, quorum sensing signals, and the characteristics of the medium, can have positive or negative influences on bacterial biofilm formation. The influences of each factor and the combined effects of multiple factors may be addressed using microfluidic approaches, which provide a promising means for controlling the hydrodynamic conditions, establishing stable chemical gradients, performing measurement in a high-throughput manner, providing real-time monitoring, and providing in vivo-like in vitro culture devices. An increased understanding of biofilms derived from microfluidic approaches may be relevant to improving our understanding of the contributions of determinants to bacterial biofilm development.     

Preparation of polymeric nanostructured materials

A procedure for forming nanostructured materials by impregnation filling of pores of poly(ethylene terephthalate) track membranes with polymeric compounds was examined. The relationships of formation of these materials were elucidated, and the structural and surface properties of these materials were studied.     

Transparent polymeric materials with elevated adhesion to silicate glass and fire resistance

Polymer–monomeric compositions consisting of polyvinylbutyral, phosphorus- chlorine dimethacrylate, and 2-hydrohypropyl-methacrylate with increased adhesion to silicate glass, fire resistance, and thermal resistance are developed. It is shown that these polymeric materials may be recommended for manufacturing fireproof glass-polymeric structures.     

Ionic gelators: oligomeric and polymeric electrolytes as novel gel forming materials

In this article, novel gel‐forming materials based on oligomeric and polymeric electrolytes for not only water but also organic solvents, including ionic liquids, are highlighted especially the synthesis, derivatization, and physical property. The oligoelectrolytes with cationic pyridinium backbone can be very easily prepared by the intermolecular quaternization of the ampholytic monomer. The ionene polymers with N,N′‐(p‐phenylene)dibenzamide linkages as polyelectrolyte were also straightforwardly synthesized in high yields by the copolymerization of 1,4‐bis[4‐(chloromethyl)benzamide]benzene and commercially available α,ω‐ditertiary amines. The oligo‐ and polyelectrolytes provided physical hydrogels under ca. 1–5 wt% of the concentrations after heating and cooling at room temperature without any other additives. These cationic gelators have characteristic properties, such as acid resistance, a self‐healing nature after mechanical collapse, and a dispersant ability for single‐walled carbon nanotubes, which have been rarely attainable for conventional physical gelators. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 10: 230–242; 2010: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.201000007     

Small molecule inhibitors of bacterial quorum sensing and biofilm formation

Bacteria monitor their local population densities using small molecules (or autoinducers) in a process known as quorum sensing. Here, we report a new and efficient synthetic route to naturally occurring bacterial autoinducers [N-acyl l-homoserine lactones (AHLs)] that is readily amenable to the synthesis of analogues. This route has been applied in the first synthesis of a library of non-native AHLs. Evaluation of these compounds in bacterial reporter gene and biofilm assays has revealed a potent set of quorum sensing antagonists. These ligands will serve as valuable new tools to explore the role of quorum sensing in bacterial pathogenesis.     

Use of noncovalent interactions to form novel liquid crystalline polymeric materials

A novel concept in polymeric liquid crystalline (LC) materials, via electrostatic grafting or complexation of functionalized mesogens and appropriate polymers, is described. It is applied to three specific systems characterized by side-chain LC architecture, two of which involve hydrogen-bonding interactions, the third ionic interactions. In these systems, complexation tends to create greater order in the mesophases present. In the hydrogen-bonded systems, the transition temperature from the isotropic state tends to decrease compared to that of the functionalized mesogen; in the ionically-bonded system, the reverse is true. At low concentrations, the mesogens act as plasticizers.     

Adhesive compositions based on perchlorovinyl resin with enhanced adhesion to polymeric elastic materials

A possibility of modifying the adhesive compositions based on perchlorovinyl resin with amino-containing compounds is studied. Aniline and N-nitrosodiphenylamine were used as amino-containing adhesion promoters. It is shown that, at an optimal content of an adhesion promoter, ED-20 resin, and plasticizer additives in the gluing composition, the bond strength of vulcanized resins based on different rubbers and linoleum increases by 1.7–3.3 times.     

Preparation of a novel polymeric fluorescent nanoparticle

A new type of narrowly dispersed fluorescent crosslinked polystyrene (PS) nanoparticles (20-50 nm) was synthesized via a modified microemulsion copolymerization of styrene, crosslinker divinyl benzene (DVB) and a hydrophilic comonomer amino ethyl methacrylate hydrochloride (AEMH), in the presence of pyrene. Characterized by steady-state fluorescence spectra, these nanoparticles show high luminescent intensity and the embedded pyrene has a negligible desorption from the nanoparticles. The emission intensity I₁ of the pyrene in the crosslinked nanoparticles is 40 times higher than that of pyrene in toluene or styrene solution with the same concentration. The fluorescence emission intensity can be varied by the amount of the monomer, crosslinker and pyrene, but is influenced little by the amount of AEMH in the range of investigation. The surface of the nanoparticles is modified by amino and amidino functional groups introduced by the comonomer and the initiator 2, 2'-azobis(2-amidinopropane) dihydrochloride (V₅₀), which controls the zeta potential on the particle surface.     

Investigation of novel composites to be used as backfill materials in radioactive waste disposal facilities

Journal of Radioanalytical and Nuclear Chemistry - The current work aims at the preparation and characterization of novel composite materials of acrylic acid/charcoal/montmorillonite (MMT) (PAACM...     

ATR-FTIR spectroscopy reveals bond formation during bacterial adhesion to iron oxide

The contribution of various bacterial surface functional groups to adhesion at hematite and ZnSe surfaces was examined using attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy. When live Shewanella oneidensis, Pseudomonas aeruginosa, and Bacillus subtilis cells were introduced to a horizontal hematite (alpha-Fe(2)O(3))-coated internal reflection element (IRE), FTIR peaks emerged corresponding to bacterial phosphate group binding. These IR peaks were not observed when bacteria were introduced to the uncoated ZnSe IRE. When cells were added to colloidal suspensions of alpha-Fe(2)O(3) at pH 7, spectra included peaks corresponding to P-OFe and nu(COOH), the latter being attributed to bridging of carboxylate at mineral surface OH groups. Selected model organic compounds with P-containing functionalities (phenylphosphonic acid [PPA], adenosine 5'-monophosphate [AMP], 2'-deoxyadenyl(3'-->5')-2'-deoxyadenosine [DADA], and deoxyribonucleic acid [DNA]) produce spectra with similar peaks corresponding to P-OFe when adsorbed to alpha-Fe(2)O(3). The data indicate that both terminal phosphate/phosphonate and phosphodiester groups, either exuded from the cell or present as surface biomolecules, are involved in bacterial adhesion to Fe-oxides through formation of innersphere Fe-phosphate/phosphonate complexes.     

Synthesis of novel fluorescent molecule and its polymeric form with aniline as fluorescent and supercapacitor electrode materials

In this study, a fluorescent material, 2‐naphthyl‐4‐amino benzoate, is synthesized by the esterification of 4‐aminobenzoic acid with 2‐naphthol. This molecule is used in the bulk polymerization of aniline, which results in the formation of poly(aniline‐2‐naphthyl‐4‐aminobenzoate). For comparison, polyaniline and also poly(aniline‐4‐aminobenzoic acid) salts are prepared via bulk polymerization. Formation and properties of these polymeric materials are evaluated by Fourier‐transform infrared (FT‐IR), ¹³C nuclear magnetic resonance, matrix‐assisted laser desorption ionization, UV‐Vis, Fluorescence, X‐ray diffraction (XRD), Field emission‐scanning electron microscopy (FE‐SEM), Differential scanning calorimetry (DSC), thermogravimetric analysis, electrical resistance and electrochemical techniques. P(ANI‐2NA4ABA) is obtained in nanofiber morphology in 106 wt% yield with respect to the amount of aniline used with comparable conductivity of conventional polyaniline salts. This polymer salt is stable up to 220°C and indicates melting at 146°C on heating and crystal formation at 128°C on cooling. This polymer shows higher wavelength fluorescence compared to the conventional polyaniline salts. This polymer is used as an electrode material without binder, which shows a specific capacitance of 360 F g^?1 at 0.25 A g^?1.     

Chaperones mainly suppress primary nucleation during formation of functional amyloid required for bacterial biofilm formation

Unlike misfolding in neurodegenerative diseases, aggregation of functional amyloids involved in bacterial biofilm, e.g. CsgA (E. coli) and FapC (Pseudomonas), is carefully regulated. However, it is unclear whether functional aggregation is inhibited by chaperones targeting pathological misfolding and if so by what mechanism. Here we analyze how four entirely different human chaperones or protein modulators (transthyretin, S100A9, Bri2 BRICHOS and DNAJB6) and bacterial CsgC affect CsgA and FapC fibrillation. CsgA is more susceptible to inhibition than FapC and the chaperones vary considerably in the efficiency of their inhibition. However, mechanistic analysis reveals that all predominantly target primary nucleation rather than elongation or secondary nucleation, while stoichiometric considerations suggest that DNAJB6 and CsgC target nuclei rather than monomers. Inhibition efficiency broadly scales with the chaperones'' affinity for monomeric CsgA and FapC. The chaperones tend to target the most aggregation-prone regions of CsgA, but do not display such tendencies towards the more complex FapC sequence. Importantly, the most efficient inhibitors (Bri2 BRICHOS and DNAJB6) significantly reduce bacterial biofilm formation. This commonality of chaperone action may reflect the simplicity of functional amyloid formation, driven largely by primary nucleation, as well as the ability of non-bacterial chaperones to deploy their proteostatic capacities across biological kingdoms.

Unlike misfolding in neurodegenerative diseases, aggregation of functional amyloids involved in bacterial biofilm, e.g. CsgA (E. coli) and FapC (Pseudomonas), is carefully regulated.     

Preparation of MgCo2O4/graphite composites as cathode materials for magnesium-ion batteries

Journal of Solid State Electrochemistry - Magnesium-ion batteries are fabricated with MgCo2O4/graphite composites as the cathode material. MgCo2O4 nanoparticles are prepared using a...     

Adsorption to metal oxides of the Pseudomonas aeruginosa siderophore pyoverdine and implications for bacterial biofilm formation on metals

The initiation of biofilm formation is poorly understood, and in particular, the contribution of chemical bond formation between bacterial cells and metal surfaces has received little attention. We have previously used in situ infrared spectroscopy to show, during the initial stages of Pseudomonas aeruginosa biofilm formation, the formation of coordinate covalent bonds between titanium dioxide particle films and pyoverdine, a mixed catecholate and hydroxamate siderophore. Here we show using infrared spectroscopy that pyoverdine can also form covalent bonds with particle films of Fe2O3, CrOOH, and AlOOH. Adsorption to the metal oxides through the catechol-like 2,3-diamino-6,7-dihydroxyquinoline part of pyoverdine was most evident in the infrared spectrum of the adsorbed pyoverdine molecule. Weaker infrared absorption bands that are consistent with the hydroxamic acids of pyoverdine binding covalently to TiO2, Fe2O3, and AlOOH surfaces were also observed. The adsorption of pyoverdine to TiO2 and Fe2O3 surfaces showed a pH dependence that is indicative of the dominance of the catechol-like ligand of pyoverdine. Infrared absorption bands were also evident for pyoverdine associated with the cells of P. aeruginosa on TiO2 and Fe2O3 surfaces and were notably absent for genetically modified cells unable to synthesize or bind pyoverdine at the cell surface. These studies confirm the generality of pyoverdine-metal bond formation and suggest a wider involvement of siderophores in bacterial biofilm initiation on metals.     

Polyester resin and carbon nanotubes based nanocomposite as new-generation coating to prevent biofilm formation

In this article, we have developed protective nanocomposite coatings using unsaturated polyester resin and multiwalled carbon nanotubes showing antimicrobial activity and mechanical durability. Carbon nanotubes retain the mechanical resilience of polyester resin in the nanocomposite, improve its hydrophobic character, and increase the adhesion features of the coating, preventing its stiffness from decreasing due to water absorption or exposure to UV rays. Nanocomposite coating exhibits an appreciable antimicrobial property and a lower level of toxicity compared to pure resin. All these features make this material a good candidate for its use in the field of anti-biofilm coatings.     

A novel model for quantification of the moisture absorption of polymeric laminated composites

In the present study, a new model was developed that considers the amount of the environmental fluid absorption by different constituents of polymeric laminated composites including fibers, resin, fiber-matrix interphase region, ply interface region, and voids. By knowing the fluid absorption behavior of the composite constituents, the present model can predict the amount of fluid absorption of different constituents of polymeric laminated composites with an arbitrary resin volume fraction and stacking sequence. Test specimens were fabricated by glass fibers and vinyl ester resin. The environmental fluids, examined in this study, were distilled and saline water under different temperatures and salt concentrations. To investigate the absorption behavior of different constituents of polymeric composite, various tests were conducted on fibers, pure cured resin, unidirectional composite specimens, and laminated composites. Based on the results of the tests, a new theoretical model was developed to quantify and predict the amount of fluid absorption of different constituents of laminated polymeric composites. The thickness of the interphase region between the fiber and matrix was also measured using the scanning electron microscope (SEM) images and nano-indentation tests. The consistency of experimental results with the outcomes of the theoretical model indicates the accuracy of the model.     

Preparation and modification of low-viscous polymeric composites in rotary-pulsatory apparatus in the self-oscillating mode

Preparation and modification of low-viscous polymeric composites in rotary-pulsatory apparatus operating in the self-oscillating mode are described. These are synthesis of antioxidant dispersions, preparation of artificial latexes from an isoprene rubber, modification of epoxy resins with low-molecular-weight carboxyl-containing rubbers, modification of cis-1,4-polyisoprene with a salt of n-nitrosodiphenylamine. The possibility of substantial intensification of these processes is analyzed.     

Determination of the flammability properties of polymeric materials: A novel method

Standard flammability tests, like the Cone Calorimeter, were developed several decades ago and provided sufficient flammability data for the purposes of the time. However, recent pyrolysis models have revealed the limitations of the standard test in providing adequate data for current flammability analysis and modelling. This paper reviews the assumptions in the standard test and proposes a novel sample holder for the cone calorimeter which incorporates a large block of aluminium at the rear face of the sample under test. This allows the heat losses at the rear face of the sample to be measured precisely and enables more accurate calculation of the material flammability properties. Tests of PA6 and a nano-composite of PA6 & Cloisite 30B, carried out using the standard and new sample holders, are presented and discussed. The peak of high heat release rate observed in standard tests of PA6 is not observed using the novel sample holder, where the burning behaviour of PA6 and the nano-composite material are largely similar. The implications of these observations are discussed.     

Polynitrile anions as ligands: From magnetic polymeric architectures to spin crossover materials

The use of polynitrile anions as ligands (L) either alone or in combination with neutral co-ligands (L′) is a very promising and appealing strategy to get molecular architectures with different topologies and dimensionalities thanks to their ability to coordinate and bridge metal ions in many different ways. The presence of several potentially coordinating nitrile groups (or even other donor groups as –OH, –SH or –NH₂), their rigidity and their electronic delocalization allow the synthesis of original magnetic high dimensional coordination polymers with transition metals ions. Furthermore, these ligands have shown coordinating and bridging capabilities in novel discrete and polymeric bistable materials (materials showing original magnetic behaviours or spin crossover (SCO) transitions). Here we report an overview of the results obtained with some of these modified polynitrile ligands, showing their rich coordination chemistry and their crucial role in new molecular materials exhibiting unusual magnetic transitions.     

Preparation and performance of novel temperature‐resistant thickening agent

In this article, a novel kind of temperature‐resistant thickening agent (LK) was copolymerized with acrylamide, acrylic acid, sodium p‐styrenesulfonate, and dimethyl diallyl ammonium chloride via free radical copolymerization. The polymerization conditions were optimized by the single‐variable method. Subsequently, the structure of the copolymer was characterized through Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. Thermal gravimetric analysis demonstrates that the thickening agent LK has an excellent ability of temperature‐resistance and the degradation temperature of the copolymer is higher than 300°C. The 3‐dimensional network structure formed in the fracturing fluid was observed via experimental results of scanning electron microscopy. Several aspects of the properties of fracturing gel system, such as temperature and shear tolerance, salt resistance and viscoelasticity, and gel breaking and filter loss were evaluated. Results indicates that the fracturing gel system presents good comprehensive performances under high‐temperature condition.