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In this work, hydrogels formed by interaction of biopolymeric electrolytes and oppositely charged surfactants are studied from the point of view of their ability to incorporate model hydrophobic dyes in their micelle-like structure. Two types of hydrogels were investigated. The first type was based on cationized dextran cross-linked by sodium dodecylsulphate. The second type was prepared by interactions of hyaluronan with carbethoxypendecinium bromide (septonex). Nile red and Atto488 were used as model dyes for the diffusion experiments. The dyes were dissolved in two different media: surfactant and physiological saline. The diffusion of dyes into hydrogel was monitored over time. Effective diffusion coefficients were determined. It was found that their values are strongly influenced by the hydrogel character, the types of dye used and the solvent. The obtained effective coefficients were higher in comparison with the values determined for the diffusion in the opposite direction (release from the hydrogel). The dyes are presented as free in physiological saline and in the form of micelles or micelle aggregates in surfactants. During diffusion into the hydrogel, they can be gradually incorporated in a “pearl necklace structure” which suppresses their mobility. In contrast, this partial immobilization of dyes can increase the concentration gradient which is a driving force of diffusion. Also, the gradual incorporation of dyes into hydrogel structures influences the values of the effective diffusion coefficients. Nilská červeň a Atto 488 byly použity jako modelová barviva pro studium transportních vlastnosttí hydrogelů připravených na bázi polyelektrolytů a opačně nabitých tenzidů. Jako polyelektrolyty byly použity kationizovaný dextran a hyaluronan dvou různých molárních hmotností. Opačně nabitými tenzidy byly SDS v případě dextranu a Septonex v případě obou hyaluronanů.

High-resolution ultrasound spectroscopy (HR-US), size and ζ-potential titrations, and isothermal titration calorimetry (ITC) were used to characterize the interactions between hyaluronan and catanionic ion pair amphiphile vesicles composed of hexadecyltrimethylammonium-dodecylsulphate (HTMA-DS), dioctadecyldimethylammonium chloride (DODAC), and cholesterol. In addition to these methods, visual observations were performed with the selected molecular weight of hyaluronan. A very good correlation was obtained between data from size titration, HR-US, and visual observation, which indicated in lower charge ratios the formation of hyaluronan-coated vesicles. On the contrary, at higher charge ratios, coated vesicles disintegrated to a size of around 2000 nm. The intensity of these interactions and the disaggregation were dependent on the molecular weight of hyaluronan. All interactions studied by ITC showed strong exothermic behavior, and these interactions between vesicles and hyaluronan were confirmed from the first addition, independently of the molecular weight of hyaluronan.

This work is focused on the study of the effect of cholesterol on the properties of vesicular membranes of ionic amphiphilic pairs at different temperatures. The hexadecyltrimethylammonium-dodecyl sulfate ionic amphiphilic pair system with the addition of 10 mol % dioctadecyldimethylammonium chloride was chosen for a detailed study of vesicle properties. A large range of cholesterol concentrations (0-73 mol %) in the temperature range 10-80 °C was studied. Under these conditions, the size distribution, the membrane fluidity, and the surface layer were monitored together with the change in the mobility of water in the surface layer. Obtained quantities were correlated with each other and combined into appropriate graphs. It was found that in stable systems that meet the condition of unimodal size distribution with a PDI value lower than 0.3, temperature has virtually no effect on the size of vesicular systems. On the contrary, when studying the hydration and fluidity of the membrane, significant changes in these parameters were found, which, however, do not affect the short-term stability of these vesicular systems. The presented results thus indicate the possibility of adjusting the composition of the vesicular system in terms of fluidity and membrane hydration while maintaining short-term stability and size distribution.

Here, we present the potential analytical applications of photochemistry in combination with fluorescence fingerprinting. Our approach analyzes the fluorescence of samples after ultraviolet light (UV) treatment. Especially in presence of metal ions and thiol-containing compounds, the fluorescence behavior changes considerably. The UV-induced reactions (changes) are unique to a given sample composition, resulting in distinct patterns or fingerprints (typically in the 230–600 nm spectral region). This method works without the need for additional chemicals or fluorescent probes, only suitable diluent must be used. The proposed method (UV fingerprinting) suggests the option of recognizing various types of pharmaceuticals, beverages (juices and wines), and other samples within only a few minutes. In some studied samples (e.g. pharmaceuticals), significant changes in fluorescence characteristics (mainly fluorescence intensity) were observed. We believe that the fingerprinting technique can provide an innovative solution for analytical detection.

This work is focused on the study of properties associated with the effect of cholesterol levels on the stability of vesicular systems based on the ion pair amphiphile hexadecyltrimethylammonium-dodecylsulphate (HTMA-DS) at laboratory temperature. The HTMA-DS catanionic system was doped with dioctadecyldimethylammonium chloride in a 9:1 M ratio and cholesterol in the amount of 0, 3, 13, 23, 33, 43, 53, 63, and 73 mol.% was added. In this system, the size distributions were studied using the dynamic light-scattering technique and the zeta potential was determined. These standard techniques were supplemented by ultrasonic and fluorescence spectroscopy techniques. Due to low stability and high opalescence of samples, spectral techniques were used only for the samples with cholesterol content above 23 mol.%. The results from High-Resolution Ultrasonic Spectroscopy and from Fluorescence Spectroscopy are in agreement. They equally point to a change in the amount of hydration water in the membrane, the largest amount of which is present in the samples with 43 and 53 mol.% cholesterol. Using the light-scattering technique, the short-term stability of prepared vesicular systems was also observed over the first 36 days. Obtained results confirmed that the most stable systems are those containing 43 or 53 mol.% of cholesterol.

In this study, three different molecules (cholesterol, phosphatidic acid, and polyethylene glycol) were used for the stabilization of liposomes during the nebulization process. The purpose of this article is to answer the question of whether the change in the composition of liposomes affected the parameters of generated aerosol and whether the nebulization process affected observed properties of liposomes. Firstly, liposomes with different composition were prepared and their properties were checked by dynamic and electrophoretic light scattering. The membrane properties were measured by fluorescence spectroscopy – especially generalized polarization (Laurdan) and anisotropy (Diphenylhexatriene). The same characteristic of liposomes was measured after the nebulization by vibrating mesh nebulizer. Cholesterol was capable of liposome stabilization because of increased membrane fluidity. The membrane properties of the outer and inner parts were not influenced by the nebulization process. Electrostatic stabilization was successful for the lowest concentration of phosphatidic acid, but after the nebulization process the hydration of the membrane outer part was changed. Higher amount of PEG needs to be added for successful steric stabilization. The nebulization process of the two lowest concentrations of PEG slightly influenced immobilized water and the rigidity of inner part of the membrane (especially around the phase transition temperature).