Browsing by Author "Lishchuk, Valeriia"

In the theoretical part of the thesis, the main trends in the study of lipid aggregates as a pseudostationary phase in capillary electrokinetic chromatography (EKC) over the past 15 years is reviewed. Due to ability of liposomes to mimic cell membranes, they have found wide application in the biomedical field and analytical chemistry. Currently, various liposomal formulations are used as background electrolyte solutions in liposome EKC. The possibility to vary the lipid content in the lipid aggregates is increasingly expanding the usage of liposome for solving specific tasks. One of the main components of vertebrate cell membranes is cholesterol. The enormous effect of this sterol on the bilipid layer has been well studied. Properties of the lipid layer in the liposomes can be altered by changing the molar percentage of cholesterol and by this it is possible to regulate and bring the experimental conditions closer to biological conditions. In the kingdom of fungi, the function of cholesterol is performed by ergosterol. The similarity of the sterols suggests that compounds would have a similar effect on the lipid bilayer. However, comparative analyses of systems involving cholesterol and ergosterol show less obvious results. Understanding the mechanisms of drug interactions with ergosterol-containing liposomes may provide ideas for the potential development of e.g., antifungal drugs. The experimental part of the thesis describes LEKC experiments with five steroids, namely 21-deoxycortisol, corticosterone, testosterone, 17α-hydroxyprogesterone, and progesterone. Two different sets of liposome formulations containing ergosterol or cholesterol were investigated. A total of nine pairs of both liposome dispersions were used as background electrolytes for the study the interactions between the liposomes and the steroids. The experimentally determined retention coefficients and the corresponding calculated distribution constants (KD) reflected the dependency of the interaction with the lipophilicity of the analytes. With increasing lipophilicity (hydrophobicity), the affinity of the steroids to the liposomes increased, as seen by stronger interactions with the lipid phase. The average relative standard deviation of the distribution constants for each steroid was not more than 5.5% for the cholesterol-rich liposomes and 4.3% for the ergosterol-rich liposomes. The regression model of log KD Ergo vs. Log KD Chol demonstrated a linear correlation between the obtained data. The linear determination coefficient (R²) was 0.9254. Pearson's linear correlation coefficient reflected also a strong linear correlation (r = 0.9615).