The effect of radiolabeled antibiotics on biofilm and microorganism within biofilm

Journal of Radioanalytical and Nuclear Chemistry - The aim of this study was to investigate the 131I and 127I labeled linezolid and moxifloxacin effects of minimum inhibitory concentration, and...     

The effect of polyolefin's molecule and supermolecule structures on some industrial processes

In this study, the raw materials and their structural properties were analyzed in synthetic polymer pipe production by the following events: 1) The effect of extruder processes to dynamic-mechanical properties of polyethylene (PE) and polypropylene (PP) pipes in pipe production; 2) The effect of the fiber direction on dynamic-mechanical properties and extruder materials; 3) The heat process on welding during the pipe production and the effect of polymer structure on welding duration; 4) Physical properties and structural changes of pigmented PE and PP raw materials. 5) The relationship between dynamic-mechanical properties of polymers with thermodynamic and kinetic concepts and effect of temperature. The results (that were) derived after several measurements are as follows: 1) The best stability properties were observed on the pipe samples which have same fibre direction. In samples with opposite and vertical fiber directions the stability properties are 30% lower. 2) The maximum dynamic-mechanical properties of the pipe samples were observed when the extruder temp. Is 463 k. These properties were lower in the pipe compared to the samples taken from the inner and outer part of the extruder. For the sample during this time the concentration of the oxygen groups are at the lowest and amorphous regions are at the highest level. These results prove that the temperature, the pressure and the cooling rate of the material taken from the extruder have too much effect on polymer structure. 3) Welding duration is investigated without changing the fibrillar structure. The best welding conditions have been obtained in case of deformation graphs with minimum areas. The results can be explained with the difference in polymer structures at different temperatures during pipe manufacturing process. 4) The σ, τ, γ values differ greatly in the samples taken from different companies (∼ 50%). The analyses of IR spectra and microphotographs show that this difference depends on the differences of the polymer structures and the initial data.     

The Ludwig–Soret effect and stochastic processes

New general stochastic models of thermodiffusion are proposed, which include velocity-dependent friction coefficient and noise tensor. These coefficients are computed exactly from the Boltzmann equation for the particular case of thermodiffusion in dilute gas mixtures. The Soret coefficients predicted by the new thermodiffusion models are computed via a Chapman–Enskog expansion and compared favorably to predictions of earlier models. In particular, the new models can accommodate for Soret coefficients of both signs, as observed experimentally.     

The MPEG effect: improving asymmetric processes by simple additives

Small amounts of simple methoxy poly(ethylene glycol)s (MPEGs) have a beneficial effect on catalyzed asymmetric aryl and alkyl transfer reactions onto aldehydes. The enantiomeric excesses of the products are improved, and this "MPEG effect" allows a reduction of the catalyst loading by a factor of 10.     

Investigating the effect of antibiotics on quorum sensing with whole-cell biosensing systems

Quorum sensing (QS) allows bacteria to communicate with one another by means of QS signaling molecules and control certain behaviors in a group-based manner, including pathogenicity and biofilm formation. Bacterial gut microflora may play a role in inflammatory bowel disease pathogenesis, and antibiotics are one of the available therapeutic options for Crohn’s disease. In the present study, we employed genetically engineered bioluminescent bacterial whole-cell sensing systems as a tool to evaluate the ability of antibiotics commonly employed in the treatment of chronic inflammatory conditions to interfere with QS. We investigated the effect of ciprofloxacin, metronidazole, and tinidazole on quorum sensing. Several concentrations of individual antibiotics were allowed to interact with two different types of bacterial sensing cells, in both the presence and absence of a fixed concentration of N-acylhomoserine lactone (AHL) QS molecules. The antibiotic effect was then determined by monitoring the biosensor’s bioluminescence response. Ciprofloxacin, metronidazole, and tinidazole exhibited a dose-dependent augmentation in the response of both bacterial sensing systems, thus showing an AHL-like effect. Additionally, such an augmentation was observed, in both the presence and absence of AHL. The data obtained indicate that ciprofloxacin, metronidazole, and tinidazole may interfere with bacterial communication systems. The results suggest that these antibiotics, at the concentrations tested, may themselves act as bacterial signaling molecules. The beneficial effect of these antibiotics in the treatment of intestinal inflammation may be due, at least in part, to their effect on QS-related bacterial behavior in the gut.     

The effect of diffusion on nanoaerosol filtration through porous materials with allowance for desorption processes

The effects of the finite residence time of aerosol particles in the bound state and their detachment due to thermal fluctuations on the filtration efficiency of porous and fibrous materials have been investigated with allowance for longitudinal diffusion in a flow. It has been shown that the desorption of particles affects the filtration efficiency even at times shorter than residence time τ_d of the particles in the bound state, while, at t ? τ_d, filtration stops. Allowance for the diffusion of aerosol particles in the flow leads to a decrease in the filtration efficiency as compared with the calculations performed without taking into account the longitudinal diffusion.     

Plasmon-based free-radical photopolymerization: effect of diffusion on nanolithography processes

This Article interrogates the mechanisms responsible for nanoscale photopolymerization induced by confined and enhanced electromagnetic fields. Surface plasmon dipolar resonance of individual Ag nanoparticles was used as an optical near-field source to locally trigger the reaction of a photopolymerizable formulation. Laser excitation of the nanoparticles embedded in the formulation reproducibly generates polymer features with typical dimensions ranging from 2 nm to a few tens of nanometer. We have determined the physicochemical parameters and mechanisms controlling the spatial extent of the photopolymerization process. We found that the diffusion of the dye is the main process limiting the polymerization reaction, as opposed to what is observed at the microscale with an equivalent chemical system. This approach demonstrates that plasmon-based polymerization can achieve true nanometer scale resolution and also provides a unique opportunity to investigate photochemistry at this length scale.     

Evaluation of retention and release processes of two antibiotics from the biocompatible core-shell microparticles

By dropwise addition of a chitosan solution into different non-solvent, such as: 1 N and 2 N NaOH as well as 1 N NaOH: C₂H₅OH mixture (2:1, v/v) at temperature of 25 °C and 50 °C under stirring, the spherical pure chitosan microparticles were performed. As solvents for chitosan was used 0.1 N acetic acid or 0.1 N HCl. The immersion of the pure chitosan microparticles in hyaluronan solution led to complex microparticles, namely chitosan microparticles covered by a hyaluronan layer. For all the microparticles performed the behaviours in the retention process of two antibiotics: chloramphenicol succinate sodium salt and cefotaxime sodium salt were analyzed. Also, the study shows the release behaviour of cefotaxime sodium salt by the microparticles loaded with this drug. Among the microparticles performed a type of complex microparticles can be considered a suitable drug delivery system for cefotaxime. These microparticles were performed by dropwise addition of chitosan solution in 0.1 N acetic acid into the 1 N NaOH: C₂H₅OH (2:1, v/v) non-solvent at 20 °C for 3 h, followed by their washing up to alkalinity loss and the immersion in hyaluronan solution of 10 g/L concentration for 24 h.     

The effect of fullerene on the resistance to thermal degradation of polymers with different degradation processes

Investigations were made about the effect of fullerene (C₆₀) on the resistance to thermal degradation of high density polyethylene (HDPE), polypropylene (PP), polymethyl methacrylate (PMMA), and bisphenol A polycarbonate (PC) matrix by using thermogravimetric analysis coupled to Fourier transform infrared spectroscopy. The results showed that the influences of C₆₀ on the resistance to the thermal degradation of different polymers were dependent on their thermal degradation mechanism. The resistance to the thermal degradation of HDPE, PP, and PMMA were improved with the addition of C₆₀, especially for HDPE matrix, which indicated that the radical trapping played a dominant role. PP and PMMA released more gaseous products at high temperature by the random scission of C–C backbone; owing to the lower bond dissociation energy of C–C in the backbone for the existence of side chains. Meanwhile, the steric hindrance of side chains also made the radicals hard to recombine with each other and accelerated the random scission, leading to the less effect on the resistance to the thermal degradation of PP and PMMA. However, few changes of resistance to the thermal degradation were found in PC matrix with the addition of C₆₀ for its non-radical degradation mechanism.     

The impact of antibiotics on bacterial cellulose in vivo

This study investigated how antibiotics, to which Gluconacetobacter hansenii is naturally resistant, impact cellulose crystallinity, allomorph, aggregation into bundles and layers, cellulose yield, and cell morphology. G. hansenii was exposed to 100 μg/mL ampicillin, chloramphenicol, and kanamycin for 7 days, and cellulose structure was analyzed using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Biomass and cellulose weights were also assessed. Ampicillin increased bundle thickness, and the bundles also showed nodular deposits indicative of non-cellulosic exopolysaccharide deposition. Ampicillin also yielded the lowest amount of cellulose per gram of biomass (p < 0.01) and induced significant filamentation behavior. Chloramphenicol inhibited biomass production (p < 0.01), increased the I-α allomorph content (p < 0.01), and also induced filamentation, though not as profusely as ampicillin. We hypothesize that defects in the peptidoglycan layer and in protein production lowered cellulose yield and promoted cells to undergo filamentation as a survival tactic. Additionally, we hypothesize that antibiotic stress caused additional exopolysaccharides to be produced and that they likely enhanced glucan chain aggregation into higher-order structures. Our findings have significant implications for downstream applications such as genetically engineering G. hansenii to produce bacterial cellulose with modified properties.     

The effect of annealing on the structure and relaxation processes of vinyl alcohol–ethylene copolymers

An annealing process has been applied to three samples of vinyl alcohol–ethylene (VAE) copolymers, richer in the former comonomer. The effect of such a process on the structure and on the relaxation mechanisms is studied. The structure of the three VAE copolymers has changed slightly. Nevertheless, the viscoelastic relaxation processes have been significantly affected for the thermal treatment. Two additional relaxations have appeared: one of them at temperatures above the relaxation associated to the glass transition, and the other at temperatures below the β mechanism of these copolymers. The temperature location, intensity, and apparent activation energy of the distinct relaxations found are discussed and compared with those in the original copolymers and the homopolymers, poly(vinyl alcohol) and polyethylene. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1–12, 2001     

How anesthetics, neurotransmitters, and antibiotics influence the relaxation processes in lipid membranes

We used pressure perturbation calorimetry to investigate the relaxation time scale after a jump into the melting transition regime of artificial lipid membranes. This time is equivalent to the characteristic rate of domain growth. The studies were performed on single-component large unilamellar and multilamellar vesicle systems with and without the addition of small molecules such as general anesthetics, neurotransmitters, and antibiotics. These drugs interact with membranes and affect melting points and profiles. In all systems, we found that heat capacity and relaxation times are linearly related to each other in a simple manner, and we outline the theoretical origin of this finding. Thus, the influence of a drug on the time scale of domain formation processes can be understood on the basis of their influence on the heat capacity profile. This allows estimations of the characteristic relaxation time scales in biological membranes.     

The effect of solvation processes on amino acid‐ and peptide‐silica stationary phases

The surface excess adsorption isotherms of water, acetonitrile, and methanol from binary hydro‐organic mobile phases were investigated on nine home‐made stationary phases with chemically bonded amino acids, dipeptides, and tripeptides using the dynamic minor disturbance method. The stationary phases were modified by the following amino acids: glycine, alanine, phenylalanine, leucine, and aspartic acid. We investigated the influence of the type of immobilized amino acids, in particular their different side chains, on the solvent adsorption. The interpretation of solvation phenomena shows significant accumulation of investigated solvents on the adsorbent surface according to their hydrophilic or hydrophobic properties. Moreover, the accumulated amount was dependent on the length and type of amino acid sequences bonded to the silica surface. Stationary phases with bonded amino acids and peptides show stronger water and acetonitrile adsorption in contrast to the stationary phase modified with aminopropyl groups—a support for the synthesis. The comparison of water and acetonitrile adsorption as well as a data obtained with the two‐site adsorption model reveal and confirm the heterogeneity of chemically bonded phases. As a consequence of performed investigations, the classification of tested stationary phases for the potential usage in particular high‐performance liquid chromatography mode was also accomplished.