Charles University Faculty of Pharmacy in Hradec Králové Department of Biophysics and Physical Chemistry Consultant: PharmDr. Jan Marek, Ph.D. Supervisor: doc. PharmDr. Veronika Nováková, Ph.D. Student: Kateřina Pekařová Title of Thesis: Cationic surface active compounds and evaluation of its properties Quaternary ammonium salts are used as surfactants in many branches of the food, pharmaceutical and chemical industries. The basic properties of these substances were studied in the thesis. The critical micellar concentration of the homologous series of five substances was determined using the conductometric method. The theory of declining critical micellar concentration with the increasing length of the side alkyl chain has been verified. The hydrolytic activity of two commonly used cationic surfactants benzalconium chloride and benzoxonium chloride for the decomposition of the organophosphorus pesticide fenitrothion was tested. For these two substances, the effect of pH and temperature changes was evaluated. The influence of tenside concentration was also monitored. Benzoxonium chloride at 50 řC and pH 11was found as the most effective hydrolytic catalyst for the decomposition of the organophosphorus pesticide fenitrothione.

Warfarin is a well-known anticoagulant drug that is used to prevent cardiovascular disease and blood coagulation such as thrombosis. In this study, the main aim was to investigate the photo physical characteristics of warfarin in the different molecular environments provided by sodium dodecyl sulfate (SDS) micelles by using ultraviolet absorption and fluorescence emission spectroscopic techniques. Warfarin and a structural analogue not existing in solution as a cyclic hemiketal, phenprocoumon, were mixed with different concentrations of SDS and spectral changes for these warfarin and phenprocoumon were recorded. Interestingly, results demonstrated, based on an evident increase in the absorption intensity at 273 nm and an evident blue shift in the fluorescence emission spectrum after the addition of an increasing concentration of SDS, that primarily the cyclic hemiketal isomer of warfarin was found to be solvated by SDS micelles at an apparent recorded critical micelle concentration of ~8mM.  Altogether these observations suggest that warfarin may be used as a molecular probe to explore the polarities of complex colloidal mixtures. Moreover, the possibility of using micelles for controlling the isomeric state of warfarin is interesting and can potentially be used for better controlling dosage of warfarin thereby reducing side effects.

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Organic materials are ubiquitous in the geologic environment, and can exert significant influence over the interfacial properties of minerals. However, due to the complexity in their structure and interaction with soil solids, their impact has remained relatively unquantified. This study investigated the engineering behaviors of organoclays, which were synthesized in the laboratory using naturally occurring clay minerals and quaternary ammonium compounds of controlled structure and density of loading. Organic cations were chosen to study the effects of functional group structure and size. The laboratory investigation showed that the presence of the organic cations on the mineral surfaces led to increased hydrophobicity of all clays tested. Conduction studies on the electrical, hydraulic, and thermal properties of the organoclay composites suggested that increasing the total organic carbon content resulted in decreased electrical and thermal conductivity, but increased hydraulic conductivity, due to the reduced swelling of the base clay mineral phase. Electrokinetic properties of the organoclays illustrated that compared with the clay's naturally occurring inorganic cations, exchanged quaternary ammonium cations were more likely bound within a particle's shear plane. Consequently, organoclays had less negative zeta potential than that of unmodified bentonite. Increasing the length of one carbon tail was more effective at binding organic cations within the shear plane than increasing the size of the cation, when compared on the basis of total organic carbon content. In terms of large strain strength, the modified organic clays exhibited increased shear strength, in part owing to the reduction in water content caused by the presence of the hydrophobic organic layering. Shear strength increased with single carbon tail length or with cation size, although the latter effect tended to reach a plateau as the length of the four short cation tails increased from 2 to 4. In terms of small strain behavior, the shear modulus was shown to be a function of the total organic carbon content. It is believed that number of particle contacts increased as the organic carbon content increased. Stiffness increased as either the size of the cation or the total organic carbon content was increased. Damping also increased as the organic loading was increased, with the organic phase acting as an energy dissipation mechanism.

The thesis deals with the study of surface-active properties, zeta potential, particle size and adhesion of surfactants (Arkopal N110, Igepal CO-520, Igepal CO-890, Dehyton PL, sodium dodecyl sulfate and dodecyltrimethylammonium bromide) selected for full notch creep test method. To determine the surface phenomena occuring in a solution due to their presence at 25, 50 and 80 °C, the Du Noüy ring method of surface tension measurement was used. The importance of factors such as concentration, ionic character and the molecular structure of the surfactants, temperature and dispersion media (pH, purity) were analysed. Dynamic light scattering measurements were performed in order to evaluate the particle size and the electrophoresis method was used to determine the zeta potential. The results were compared to the contact angle measurements, i. e. adhesion tendency between surfactant solutions and the surface of selected types of high density polyethylene. The optical analysis was used to evaluate the contact angle. The negative impact of water purity was negated. The temperature dependecy was specific for each of the examined surfactant species, however the relationship between temperature and the length of hydrophilic chain was discovered. Alkaline pH was less convenient for amphoteric surfactant than acid or neutral environment, but this might have been caused by components contained in the buffer. The character of surfactant solutions was mostly monodisperse. The only exceptions were 1mM Igepal CO-520 and 3mM Dehyton PL. Further investigation led to conclusion that the molecules tend to form agglomerates. Adhesion was in accordance with surfactant effectiveness of surface reduction and adsorption. However, this theory did not match the data obtained from testing acid and neutral Dehyton PL solutions' adhering to polyethylene species containing carbon black.

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This work deals with the current topic of carrier systems. Since the biggest problem is the passage of hydrophobic drugs through the bloodstream, or through universal body barriers (eg blood-brain), it is necessary to chemically modify these carriers in order to be able to administer hydrophobic substances effectively. Based on a literature search, several systems are designed and subsequently studied, in which there is a presumption of possible use for carrier systems and at the same time they have biosurfactants incorporated in them due to their ability to solubilize hydrophobic molecules. The theoretical part of this work will describe the individual biosurfactants, the process of their production, their physicochemical properties, and the possibility of their use in carrier systems. At the same time, the individual carrier systems, the procedure of their preparation, the possibilities of their use are described, and their advantages and disadvantages are also compared. In the practical part, the screening of both individual substances and their mutual interactions, as well as methods used to study the emerging structures is then performed. The study of molecular interactions is primarily performed using the technique of dynamic light scattering. The next part describes the optimization of hydrogel formation with incorporated biosurfactants in their structure and then the formed gels are subjected to rheological and solubilization tests. The study of the internal structure of these gels is performed using a scanning electron microscope.

This disertation thesis is focused on the study of physico-chemical interactions of hyaluronan (with molecular weights from 10 to 1750 kDa) with cationic surfactants measured using uncommon technique named high resolution ultrasonic spectroscopy. Densitometer was also used for the study of these interactions, in measuring of density and ultrasonic velocity of hyaluronan with different molecular weight in dependence on elevated temperature (25 50 °C). The aim is the determination of critical micelle concentration (CMC) and critical aggregation concentration (CAC) of the suractants in the absence and in the presence of hyaluronan with various molecular weights. Interactions in this system are important for the design of the systems for the targeted delivery, especially for the drugs. The experiments were made in water and sodium chloride solution. The significant breakpoint in the ultrasonic velocity showed changes in the system hyaluronan-surfactant.

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