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Charles University, Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Technology Author: Eliška Šrámová Supervisor: Dr. Georgios Paraskevopoulos, Ph. D Consultant: Mgr. Anna Nováčková Title of Thesis: Study of the effect of cholesterol concentration on monolayer models Skin is composed of 3 major layers: hypodermis, dermis, and epidermis. The uppermost layer, which is called stratum corneum (SC), has a unique structure resembling a well-built wall. Corneocytes represent bricks and the lipid matrix works like a mortar. Ceramides, free fatty acids, and cholesterol (Chol) are the main lipids creating the human SC matrix. In a healthy SC, the ratio of these lipids is equimolar. This ratio is crucial, not only to maintain the barrier function of the skin, but also for the organization of lipids in SC. Chol appears to be required for the correct lamellar organization, and the ordering of lipids inside of the lamellar formation (lateral organization) in SC. Abnormalities in the ratio of the lipids and depleted amount of Chol can lead to a disruption of the skin barrier function resulting in skin disease or multisystemic diseases (e.g. X-linked ichthyosis, Conradi-Hünermann-Happle syndrome, and CHILD syndrome.) The present work deals with a Chol deficiency study on lipid organization on...

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Self-assembled monolayers on gold and glass substrates are employed as templates to direct the crystal growth and polymorphism of active pharmaceutical ingredients. Orthogonal approaches are used to control polymorphism either through complementary hydrogen-bonding interactions or through repulsive interactions.

"Previous studies carried out in our laboratory resulted in the development of noncovalently assembled multilayered thin films incorporating metal ions such as Cu(II) and organic ligands including dicarboxypyridine. In one study, a SAM consisting of 4-[(10- mercaptodecyl)oxy]pyridine-2,6-dicarboxylic acid was deposited on gold. The pyridine group was then used to complex a layer of Cu(II) ions which in turn were capped by cis- 2,2’-dipyridylethylene. This stilbene analog undergoes photoinduced cis-trans isomerization on the surface resulting in a substantial increase in the hydrophilicity of the surface leading to the possibility of creating virtual microfluidic valves and pumps. However, the photoswitchable wettability was irreversible. Stilbene-4,4-dicarboxylic acid was the ligand selected for generating a reversible system. The decision to use this stilbene moiety was based on molecular modeling and the commercial availability of both cis and trans forms. When 4-[(10-mercaptodecyl)oxy]pyridine-2,6-dicarboxylic acid was used as SAM, the stilbene-4,4’-dicarboxylic acid did not undergo photoisomerization. Prolonged irradiation leads to photodegradation of film. A mixed SAM of dodecanethiol and mercaptoundecanoic acid was used to create space on the surface and facilitate isomerization. But cis-trans isomerization of the stilbene moiety was not achieved by this system. When a mixed SAM of 4-[(10-mercaptodecyl)oxy]pyridine-2,6-dicarboxylic acid and 4-tert butylbenzenethiol was used, stilbene-4,4-dicarboxylic acid showed reversible photoinduced cis-trans isomerization for one complete cycle leading to a reversible change in wettability. After one cycle of isomerization the film photodegrades."

Amphipathic molecules are basically long chains, one end of which likes water (is hydrophilic) and the other end abhors it (is hydrophobic). These molecules tend to sit vertically in a fluid and adhere to each other. This attraction of adjacent molecules causes the molecules to condense into regions, referred to as polymer Langmuir layer domains, which are a single molecule thick and behave like a two dimensional fluid. This attraction also manifests itself as a line tension, analogous to surface tension in a fluid droplet, which causes the regions to become circular as they attempt to minimize the length of their perimeter. Often the layer will form holes, gaps in the liquid monolayer which contain a much smaller density of molecules. In the presence of humidity, the holes are observed to close up, pulled together by the line tension as well as condensation of the hole molecules at the boundary. Previous researchers have computed the fluid velocity for the process when the hole is assumed to be a vacuum. I, however, propose to replace this model with a gas, adding condensation of gas from the hole into the liquid domain of the monolayer to the line tension force. The hope is to obtain a mathematical model that better corresponds to the physical problem than current models do.

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