Chitosan-based matrix as a carrier for bacteriophages

Wound healing is a dynamic and complex process where infection prevention is essential. Chitosan, thanks to its bactericidal activity against gram-positive and gram-negative bacteria, as well as anti-inflammatory and hemostatic properties, is an excellent candidate to design dressings for difficult-to-heal wound treatment. The great advantage of this biopolymer is its capacity to be chemically modified, which allows for the production of various functional forms, depending on the needs and subsequent use. Moreover, chitosan can be an excellent polymer matrix for bacteriophage (phage) packing as a novel alternative/supportive antibacterial therapy approach. This study is focused on the preparation and characteristics of chitosan-based material in the form of a film with the addition of Pseudomonas lytic phages (KTN4, KT28, and LUZ19), which would exhibit antibacterial activity as a potential dressing that accelerates the wound healing. We investigated the method of producing a polymer based on microcrystalline chitosan (MKCh) to serve as the matrix for phage deposition. We described some important parameters such as average molar mass, swelling capacity, surface morphology, phage release profile, and antibacterial activity tested in the Pseudomonas aeruginosa bacterial model. The chitosan polysaccharide turned out to interact with phage particles immobilizing them within a material matrix. Nevertheless, with the high hydrophilicity and swelling features of the prepared material, the external solution of bacterial culture was absorbed and phages went in direct contact with bacteria causing their lysis in the polymer matrix. KEY POINTS: • A novel chitosan-based matrix with the addition of active phages was prepared • Phage interactions with the chitosan matrix were determined as electrostatic • Phages in the matrix work through direct contact with the bacterial cells.

Subdiffusion equation with Caputo fractional derivative with respect to another function in modeling diffusion in a complex system consisting of a matrix and channels

Anomalous diffusion of an antibiotic (colistin) in a system consisting of packed gel (alginate) beads immersed in water is studied experimentally and theoretically. The experimental studies are performed using the interferometric method of measuring concentration profiles of a diffusing substance. We use the g-subdiffusion equation with the fractional Caputo time derivative with respect to another function g to describe the process. The function g and relevant parameters define anomalous diffusion. We show that experimentally measured time evolution of the amount of antibiotic released from the system determines the function g. The process can be interpreted as subdiffusion in which the subdiffusion parameter (exponent) α decreases over time. The g-subdiffusion equation, which is more general than the "ordinary" fractional subdiffusion equation, can be widely used in various fields of science to model diffusion in a system in which parameters, and even a type of diffusion, evolve over time. We postulate that diffusion in a system composed of channels and a matrix can be described by the g-subdiffusion equation, just like diffusion in a system of packed gel beads placed in water.

Experimental and Theoretical Analysis of Metal Complex Diffusion through Cell Monolayer

The study of drugs diffusion through different biological membranes constitutes an essential step in the development of new pharmaceuticals. In this study, the method based on the monolayer cell culture of CHO-K1 cells has been developed in order to emulate the epithelial cells barrier in permeability studies by laser interferometry. Laser interferometry was employed for the experimental analysis of nickel(II) and cobalt(II) complexes with 1-allylimidazole or their chlorides’ diffusion through eukaryotic cell monolayers. The amount (mol) of nickel(II) and cobalt(II) chlorides transported through the monolayer was greater than that of metals complexed with 1-allylimidazole by 4.34-fold and 1.45-fold, respectively, after 60 min. Thus, laser interferometry can be used for the quantitative analysis of the transport of compounds through eukaryotic cell monolayers, and the resulting parameters can be used to formulate a mathematical description of this process.

How to determine a boundary condition for diffusion at a thin membrane from experimental data

We present a method of deriving a boundary condition for diffusion at a thin membrane from experimental data. Based on experimental results obtained for normal diffusion of ethanol in water, we show that the derived boundary condition at a membrane contains a term with a Riemann-Liouville fractional time derivative of order 1/2. Such a form of the boundary condition shows that a transfer of particles through a thin membrane is a "long-memory process." The presented method is an example that an important part of the mathematical model of physical processes may be derived directly from experimental data.

The effects of nickel(II) complexes with imidazole derivatives on pyocyanin and pyoverdine production by Pseudomonas aeruginosa strains isolated from cystic fibrosis

Pseudomonas aeruginosa infection is problematic in patients with cystic fibrosis (CF). P. aeruginosa secretes a diversity of pigments, such as pyocyanin and pyoverdine. The aim of this study was to evaluate the effects of complexes of nickel(II) ([Ni(iaa)2(H2O)2]·H2O (iaa = imidazole-4-acetate anion), [Ni(1-allim)6](NO3)2 (1-allim = 1-allylimidazole) and NiCl2 on pyocyanin and pyoverdine production by 23 strains of P. aeruginosa isolated from cystic fibrosis under growth conditions specific for the CF respiratory system. The antibacterial effects and biophysical properties of the tested substances were measured by spectrofluorometric techniques, as well as by laser interferometry, confocal and atomic force microscopy. The cytotoxic properties of all compounds were measured by Annexin/IP assay against A549 cells. All tested compounds have no effect on pyocyanin production and decrease the pyoverdine secretion in about 40% of tested P. aeruginosa strains at non-cytotoxic range of concentrations. Imidazole-4-acetate anion and 1-allylimidazole have good diffusion properties in the mature P. aeruginosa PAO1 biofilm. In conclusion, the tested nickel(II) complexes do not have clinical implications in P. aeruginosa eradication in cystic fibrosis. The diffusion properties of 1-allylimidazole and imidazole-4-acetate and their lack of effect on A549 cells suggest that they might be considered for chemical synthesis with other transition metals.

Laser interferometric investigation of solute transport through membrane-concentration boundary layer system

We investigate diffusive transport in a membrane system with a horizontally mounted membrane under concentration polarization conditions performed by a laser interferometry method. The data obtained from two different theoretical models are compared to the experimental results of the substance flux. In the first model, the membrane is considered as infinitely thin, while in the second one as a wall of finite thickness. The theoretical calculations show sufficient correspondence with the experimental results. On the basis of interferometric measurements, the relative permeability coefficient (ζ_s) for the system, consisting of the membrane and concentration boundary layers, was also obtained. This coefficient reflects the concentration polarization of the membrane system. The obtained results indicate that the coefficient ζ_s of the membrane-concentration boundary layer system decreases in time and seems to be independent of the initial concentration of the solute.

Laser interferometric analysis of glucose and sucrose diffusion in agarose gel

The paper presents the investigation results of glucose and sucrose diffusion in agarose gel studied with laser interferometry method and the results of fluorescence analysis of the macroscopic gel structure. The diffusion kinetics of these substances released from aqueous solutions of a molar concentration of 0.05 M into the agarose solutions of concentrations of 0.5% and 3% in two gravitational configurations of measuring system was analysed. In the first configuration the solute diffused according, whereas in the second one - opposite to the gravitational force. The diffusion was analysed in the time period between 120 and 2400 s with a time interval of Δt = 120 s. We observed that the convective instabilities were damped well by the agarose gel, which gives the possibility of the interferometric studies of the diffusive transport for other substances in different gravitational configurations of the system. The time characteristics of glucose and sucrose fluxes in both configurations of the system and the gravitational polarisation coefficient values were obtained. The substantial differences in fluxes of glucose and sucrose diffused according and opposite to the gravitational force were observed. Additionally, we observed the differences between the diffusive fluxes of these substances in both configurations in dependence on the gel solution concentration (which is associated with gel porosity dependent on its concentration) and the kind of diffused substance.

Morphological changes in Proteus mirabilis O18 biofilm under the influence of a urease inhibitor and a homoserine lactone derivative

Proteus mirabilis is a pathogenic gram-negative bacterium that frequently causes kidney infections, typically established by ascending colonization of the urinary tract. The present study is focused on ureolytic activity and urease inhibition in biofilms generated by P. mirabilis O18 cells. Confocal microscopy revealed morphological alterations in biofilms treated with urea and a urease inhibitor (acetohydroxamic acid, AHA), as some swarmer cells were found to protrude from the biofilm. The presence of a quorum-sensing molecule (N-butanoyl homoserine lactone, BHL) increased biofilm thickness and its ureolytic activity. Laser interferometric determination of diffusion showed that urea easily diffuses through P. mirabilis biofilm, while AHA is blocked. This may suggest that the use of urease inhibitors in CAUTIs may by less effective than in other urease-associated infections. Spectroscopic studies revealed differences between biofilm and planktonic cells indicating that polysaccharides and nucleic acids are involved in extracellular matrix and biofilm formation.

Laser interferometry analysis of ciprofloxacin and ampicillin diffusion from liposomal solutions to water phase

The paper presents experimental investigations of diffusion of antibiotics (ciprofloxacin or ampicillin) into the water phase from mixtures of neutral or negatively charged liposomes, and antibiotic-liposome interactions. Using the laser interferometry technique, the amounts and fluxes of released antibiotics, concentration field evolution, and the velocity of the concentration boundary layer's "growth" were determined. To avoid the limitations of membranes, a measurement system without the artificial boundary of phases with a free water-solution interface has been proposed. It was found that the diffusion of anionic and neutral liposomes into the water phase was insignificant and mainly the diffusion of antibiotics was measured. Differences in the diffusion kinetics of ciprofloxacin and ampicillin from liposomal solutions to the water phase were observed. Ampicillin diffused more efficiently than ciprofloxacin regardless of the liposomal solution type. Moreover, the amount of ampicillin and ciprofloxacin released from the anionic liposomal phase was higher than that from the neutral one. Our results confirm that ciprofloxacin at neutral pH shows little tendency to bind neutral liposomes. Additionally, it was also observed that ciprofloxacin disrupts negatively charged liposomes as a final effect of antibiotic-lipid interactions.

The Investigation of Time-dependent Solute Transport through Horizontally Situated Membrane: The Effect of Configuration Membrane System

This paper presents an experimental and theoretical investigation ofsolute transport through a horizontally situated membrane. Theexperimental investigation was carried out by the laserinterferometric method in association with a computer system ofinterference image analysis. On the basis of this analysis thicknessof near-membrane layers, solution concentration drops on these layersas well as diffusion fluxes of diluted substance are determined.Different fluxes of the soluble substance are observed depending onthe configuration of the system. The results of the experimental andtheoretical investigation of diffusion fluxes are conformable inrespect of measurement error, with one adjustment parameter, i.e. thesolute partition coefficient.

Analysis of ciprofloxacin and gentamicin diffusion in Proteus mirabilis O18 biofilm by laser interferometry method

Laser interferometry is a measurement technique used in physical sciences, with a potential for new applications in microbiology. Our previously studies, focused on the quantitative analysis of antibiotics diffusion through membranes or their releasing from gel structure, indicate that this method might be useful in analysis of substances diffusion across the bacterial biofilms. As antibiotic - biofilm interaction model, we tested above method for determination of ciprofloxacin or gentamicin diffusion through Proteus mirabilis O18 biofilm. Laser interferometry analysis of antibiotics diffusion showed that the amount of ciprofloxacin transported through mature biofilm is 1.9 times higher than gentamicin. It was correlated with lower level of gentamicin in compare to the level of ciprofloxacin in biofilm, which amounts were predicted in biofilm during diffusion process by laser interferometry method. We suggest that the analysis of antibiotic diffusion in biofilm might by helpful in evaluation of effectiveness of antibacterial agents.

Analysis of ciprofloxacin and gentamicin diffusion in Proteus mirabilis O18 biofilm by laser interferometry method

Laser interferometry is a measurement technique used in physical sciences, with a potential for new applications in microbiology. Our previously studies, focused on the quantitative analysis of antibiotics diffusion through membranes or their releasing from gel structure, indicate that this method might be useful in analysis of substances diffusion across the bacterial biofilms. As antibiotic - biofilm interaction model, we tested above method for determination of ciprofloxacin or gentamicin diffusion through Proteus mirabilis O18 biofilm. Laser interferometry analysis of antibiotics diffusion showed that the amount of ciprofloxacin transported through mature biofilm is 1.9 times higher than gentamicin. It was correlated with lower level of gentamicin in compare to the level of ciprofloxacin in biofilm, which amounts were predicted in biofilm during diffusion process by laser interferometry method. We suggest that the analysis of antibiotic diffusion in biofilm might by helpful in evaluation of effectiveness of antibacterial agents.